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Language-induced voice quality variability in bilinguals
Journal of Phonetics (1994) 22, 19-31
Language-induced voice quality variability in bilinguals Marielle Bruyninckx and Bernard Harmegnies Service de Ia communication parlee, Universite de Mons-Hainaut, B-7000 Mons, Belgium
Joaquim Llisterri and Dolors Poch-Oiive Departament de Filologia Espanyola, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Spain Received 22nd May 1991, and in revised form 8th February 1993
The paper examines whether the language spoken exerts influences on a speaker's voice quality. Bilingual (Catalan/Spanish) subjects were studied in order to neutralize the speakers individual characteristics. The Long Term Average Spectrum (LTAS) was used as an acoustical measure of voice quality. The sample of 12 males and 12 females was divided into two categories of linguistic dominance (Catalan and Spanish dominances). Each subject produced five repetitions each of a Spanish and a Catalan phonetically balanced text. A 400-line LT AS was computed for each repetition; the 240 spectra so obtained were compared by means of a pattern recognition procedure (SDDD dissimilarity index). Within-speaker comparisons of two kinds were performed: the between-language (Catalan/Spanish) and the within-language (Catalan/Catalan and Spanish/Spanish) ones. The between-language variability was higher than the within-language variability, irrespective of the sex and language dominance categories. The data, moreover, exhibited a tendency towards greater within-language variability in the dominant language than in the non-dominant one. Finally, a greater correlation in the Catalan dominant group between intra- and inter-language LT AS dissimilarities suggests differences in the mastery of the second language between the two dominance groups.
1. Introduction
Many experimenters involved in acoustical analysis of voice quality have based their works upon the use of Long Term Average Spectra (LT AS). Both theoretical and empirical reasons seem to plead for their choice. On the one hand, remembering the definition that Abercrombie (1967:91) gave for the concept of voice quality ("[voice quality] is a quasi-permanent quality running through all the sound that issues from his [the speaker's] mouth") , it seems quite reasonable to apply an averaging process to speech samples in order to peutralize the short-term segment characteristics and thus collect phoneme-independent speaker-dependant information. This is definitely the purpose of long-term spectra, which are made of instantaneous spectra averaged over a sample of speech "long enough for the effect of individual linguistic segments 0095-4470/94/010019 + 13 $08.00/0
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no longer to be significant" (Nolan, 1983:130). On the other hand, many experiments have established the validity of the LT AS taken as an acoustical cue to the speaker's identity, mainly in the field of speaker recognition (Ramishvili, 1970; Gubrynowicz, 1971; Furui, ltakura & Saito, 1972, 1975; Majewski & Hollien, 1974; Zalewski, Majewski & Hollien, 1975; etc.). Experiments dealing with abnormal voices have, moreover, proved its sensitivity to special phonation types (e.g., in deaf subjects, Formby & Monsen, 1982; Plant, 1983; esophageal voices, Weinberg, Horii & Smith, 1980; voice after surgery , Fritzell, Hallen & Sundberg, 1974; Finck & Harmegnies, forthcoming). Other experiments (Nolan, 1983; Harmegnies, Bruyninckx , Llisterri & Poch, 1989) have also shown important correlations between LTAS variations and the use of specific "settings" as described by Laver (1980). The long-term spectrum therefore appears as a promising tool for the study of voice quality , or at least for substantial aspects of it. Among the determinants of voice quality, variables such as the speaker's sex, age, emotional state and social origin, have received special attention. Whether the language spoken should be considered or not as a supplementary source of the voice quality variability is nevertheless still an open debate. Most experiments dealing with this topic have focused on the popular conception that languages could be characterized each by specific overall spectral tendencies. However, no precise conclusion can be drawn from these works. Some authors have reported significant effects of the language spoken by a given speech community on the long-term spectral features of individual speakers (Tarn6czy, 1958, 1962; Banuls-Terol, 1971; etc.), while others failed to find a correlation between these factors (Lorand, Minier & Saliou, 1975; Boullosa & Perez Ruiz, 1984; etc.) . The consistency of the results obtained in the field of speaker recognition is no greater, since different experiments dealing with various languages have led to apparently contradictory results. In this respect, Nolan (1983) emphasizes the apparent conflict between Tosi 's (1979) results showing a relative invariance in the long-term average spectrum (LTAS) for a given speaker and Majewski & Hollien's (1975), suggesting a language effect on the speaker's LT AS. Harmegnies & Landercy (1985) have reviewed the descriptive research in the field of voice quality, showing the lack of efficient ways of quantifying the observed variability. They have also suggested that, in some cases, at least part of the assumed language effects reported might be attributed to intrinsic individual variability. They therefore focused on bilingual speakers (French/Dutch), in order to neutralize it. A mixed quantitative/qualitative methodology has been developed, allowing careful examination of the differences between languages, notwithstanding the speaker-related variability. The results confirmed the existence of a significant language-related component of long-term spectral variability, but also revealed that language effects are smaller than individual effects (Harmegnies & Landercy, 1985; Harmegnies, Landercy and Bruyninckx, 1987). These findings make it possible to understand some of the reasons for the apparently contradictory conclusions in previously published experiments , but they also show the need for applying the same methodology to other languages. In this paper we will report on our joint research concerning differences in long-term spectral features related to the use of Castillian Spanish as opposed to Catalan in bilingual speakers of these languages.
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2. Sociolinguistic background We will refer in this study to subjects living in the area of Barcelona (Catalonia, Spain). Catalan and Spanish are the official languages of the autonomous community of Catalonia; they are both taught at school and used in the media and in everyday communication. Both monolingual and bilingual speakers are found among the population of Catalonia. Catalan monolingualism is a very unlikely possibility, due to the official character of Spanish in Spain. Monolingual Spanish speakers are mainly to be found among recently arrived immigrants to Catalonia. They may be speakers of any variety of peninsular Spanish. Bilingual subjects range from native Catalan speakers who know standard Spanish (which is the official language of the whole State) to native Spanish speakers with different dialectal backgrounds who have acquired Catalan as a second language, with greater or lesser proficiency. Due to those socio-linguistic factors, most bilingual speakers in Catalonia therefore exhibit either Catalan or Spanish dominance. This paper will focus on subjects with a fairly equal knowledge of both languages, but showing a degree of language dominance either in Catalan or in Spanish .
3. Experiment 3.1. Selection of subjects The choice of speakers was made according to answers to a written questionnaire, introduced by Viladot (1981), administered to a large group of first year university students at the Universitat Autonoma de Barcelona. The questions addressed their use of Catalan and Spanish in four different skills: listening, speaking, reading and writing. Subjects had to give a subjective percentage figure representing their use of each language in a series of specific environments or situations (at home, with friends, at the University, at work, in everyday activities in town, communicating with the Administration, etc.) . This gave an estimate of their patterns of language use for each activity related to the above-mentioned skills. Questions about geographical origins and language background in the family have also been included. A sample of 24 bilingual subjects has been retained for the present study . They are all bilingual, but their use of Catalan and Spanish exhibits different tendencies: in half of the group the percentage of use is at least 60% for Catalan, and at most 40 % for Spanish in at least two-thirds of the situations examined for each skill-those being the Catalan-dominant subjects; the other half, the Spanishdominant speakers, shows the opposite linguistic behaviour. Spanish-dominant subjects are all users of standard peninsular Spanish . Moreover, since the degree of LT AS variability has turned out to be sex-dependent (Harmegnies, 1988a ), both male and female subjects were recorded. The population studied then is as follows : six male and six female bilinguals with Catalan dominance, and six male and six female bilinguals with Spanish dominance. 3.2. Corpus A phonetically balanced text was prepared for each language (see the Appendix) following the phonetic distribution reported for Catalan by Rafel (1979) and for
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Spanish by Navarro Tomas (1946). The Catalan corpus consisted of 177 vowels and 210 consonants with a total of 387 phonological units, whereas the Spanish one consisted of 209 vowels and 231 consonants, yielding a total of 440 units. Figure 1 compares the distribution of phonemes in the text with their general distribution in both languages. The texts lasted for about 20 s and were read at the speaker's natural rate.
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3. 3. Experimental setting Five repetitions of each text were recorded for each subject. The recordings took place in a sound-proof room, with the speakers sitting in front of a microphone placed at a constant distance of 20 em from the mouth. A Revox A 77 tape recorder and a Sennheiser MD 441N cardioid microphone were used. 3.4. Acoustical analysis The procedure we used to compute our LTAS is of the same type as those used in classicallitterature about long-term spectra (Furui et al., 1975; Zalewski et al., 1975; Hollien & Majewski, 1977; etc .), i.e., it allows straightforward averaging of the whole portion of signal taken into account, notwithstanding the kind of segments contained in it. The built-in so-called "linear" averaging procedure of a Briiel & Kjaer 2033 analyser was selected for that purpose . This device, which was previously used by several experimenters (Frokjaer-Jensen & Prytz, 1976; Boullosa & Perez Ruiz, 1984; Dejonckheere, 1984; etc.) is based upon a converging algorithm which allows real-time averaging of the input signal, and thus does not require that the signal duration be known in advance. It is therefore possible to interrupt the averaging process at any time , on the basis of aural control of the input signal (e.g., in order to reject noisy segments , or unexpected repetitions of words, etc.) In the case of the present experiment, averaging was stopped just after the end of each corpus utterance. This procedure ensures invariance of the speech material accounted for by all the LTAS across utterances, speakers and groups in each language. This was not achieved in experiments by other authors where the integrating time was held constant, leaving room for corpus-induced variability. 3. 5. Comparison procedure
3. 5.1. Dissimilarity measure For the purpose of assessing language-induced effects on the long-term spectrum, a quantitative methodology has been used . Comparisons of the shapes of the LT AS were performed by means of a pattern-matching measure, the SDDD index (Harmegnies, 1988b ), defined as follows : p ,u .. r/'lt,r r-_rv ~~-' {d!r 1 k L£,YV' ~ 1"""\ , SDDDss' = - ~ (S;- Sf- M") 2 iY ~~.ff:._(Ji)_
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where S and S' are the spectra being compared, each one defined by its s; and sf level values for each of the k frequency components, and M" is the mean for the S;- Sf differences. As equation (1) shows, SDDD is the Standard Deviation of the Differences Distribution. If the shapes of the spectra compared are highly similar, the S;- Sf differences deliver values that vary little across the frequency components and the standard deviation is therefore small. If the shapes are different , large level differences can be found in certain frequency channels, and small ones in others and the standard deviation of the S;- Sf differences therefore increases. Hence SDDD is a dissimilarity index: high SDDD values indicate considerable dissimilarity between spectra. Moreover, being insensitive to variations in the overall levels of the
M. Bruyninckx et al. compared spectra, SDDD does not need any intensity normalization prior to the computation. 3.5.2. Comparison types Two types of within-speaker comparisons of the stored LT AS were performed for each subject: between-language comparisons and within-language comparisons. In the case of the between-language comparisons (Catalan vs. Spanish), each Catalan LT AS of each subject was matched against each Spanish LTAS of the same subject; this procedure resulted in 600 between-language/within-speaker comparisons (25 comparisons x 2 dominance groups x 2 sexes x 6 subjects). For the within-language matchings (i.e ., Catalan vs. Catalan , and Spanish vs. Spanish), one comparison was performed for each possible non-redundant pair of the five LTAS in each language for each one of the 24 speakers, i.e., 10 comparisons by subject and by language, thus 480 within-speaker comparisons for the whole sample (2 languages x 2 sexes x 6 subjects x 10 matchings x 2 dominance groups). Thus, a total of 1080 comparisons have been performed altogether. 4. Results
An exhaustive presentation of the whole set of 1080 dissimilarity values being impossible, the results of the comparison procedure described above have been summarized . They are shown in Fig. 2, where lowest and highest values, together with means and standard deviations of the SDDD index , have been plotted for each subject and each comparison condition. Overall statistics are given in Table I for each comparison condition in each sex/language dominance subgroup of six speakers. It can be easily seen from Figs 2(a)-(d) that the SDDD values drawn from within-language comparisons exhibit the same tendencies as reported by Harmegnies (1988a ), on the occasion of within-language comparisons of various French LTAS: the average SDDD values score around 2.5 for men and 3.2 for women . As usual , the data show a considerable amount of between-speaker variability: the individual average SDDD values vary from 1.93 to 4.43 for Catalan vs . Catalan, from 1.83 to 4.59 for Spanish vs. Spanish , and from 2.41 to 5.03 for Catalan vs. Spanish. An examination of the groups' central tendencies shows that the SDDD index values derived from between-language comparisons tend to score higher than those drawn from within-language matchings. This relationship can be observed in Table I for the average values in each sex/dominance group . This tendency appears moreover to be very strong, since the relationship holds true for each one of the 24 speakers in the sample (see Fig. 2 where the third bar consistently shows the largest mean). Although the language effect appeared rather obvious on the basis of this simple descriptive study of the results , we nevertheless decided to confirm its significance by inferential means. For that purpose , we considered the average SDDD for each subject in each comparison condition as an overall measure of his or her voice quality variability. Our hypothesis was that the speakers would exhibit a greater voice consistency intralingually than inter-lingually (i .e ., their between-language
Voice quality and bilingualism
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Figure 2. Bar graph showing means ± standard deviation, and lower and upper values for each comparison condition (for each subject, the order of bars from top to bottom is: CAT/CAT, SPAN/SPAN, CAT/SPAN). (a) Catalan-dominant males; (b) Catalan-dominant females ; (c) Spanish-dominant males; and (d) Spanish-dominant females.
26
M. Bruyninckx et al. TABLE I. Grand means of the SDDD values for each language dominance/sex subgroups in each comparison condition
Catalan vs. Catalan
Castilian vs. Castilian
Catalan vs. Castilian
Catalan Males Females Castilian Males Females
2.34 3.27
2.08 3.24
3.11 4.00
2.54 3.04
2.58 3.35
2.98 3.80
All
2.80
2.81
3.47
voice quality variability would be significantly greater than their within-language one). We first applied the treatment as in our previous research (Harmegnies et al., 1989). In that experiment, a homogeneous group of bilingual subjects was studied so that language dominance and sex did not vary. Three comparison conditions were established as in the present study: Catalan/Catalan, Spanish/Spanish and Catalan/Spanish. An overall comparison of these three conditions revealed a significant between-conditions effect; nevertheless, once the between-language (Catalan/Spanish) comparisons were removed, the same processing resulted in a lack of significance. Thus, according to this study, the between-condition differences were attributed to between-language differences only. In order to reproduce the treatment with our new data, we performed a one-way non-parametric Friedman analysis of variance performed on the whole group of 24 subjects , disregarding dominance and sex category. The three data sets under analysis consisted of average SDDD values drawn from the three comparison conditions (within-language Catalan; within-language Spanish; between-language). As in previous research, there was a significant effect of comparison condition (Friedman analysis of variance: chi-square= 6, df = 2, p < 0.001). As the difference between the first two comparison conditions (i.e., both within-language) is very small (overall averages are , respectively, 2.80 and 2.81) and not significant at all (Wilcoxon test , p = 0.8864), it appears very clearly that the overall effect of condition is due to differences between the intralanguage and the inter-language values. The analyses thus confirm our earlier results. A closer examination of the results, taking into account the subjects' linguistic dominance, nevertheless suggests the existence of sources of variability that were not observed previously . Table I shows that in Catalan dominant speakers, the CAT /CAT SDDD values tend to score higher than the SPAN /SPAN ones, and the opposite relationship can be observed in Spanish dominant subjects . This informal observation was tested by inferential analysis: the whole sample was split by language dominance (i .e., we made two groups of 12 speakers , with the same language dominance in each group), and we performed again inferential tests aimed at comparing the two within-language comparison conditions. This revealed significant differences between the two
Voice quality and bilingualism
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within-language comparison conditions in both language groups (Wilcoxon test, Catalan-dominant group: p = 0.0499; Wilcoxon test, Spanish-dominant group: p = 0.0499). These results therefore could suggest a new idea: voice consistency in bilinguals is greater in the non-dominant language; between-language variability is nevertheless greater than within-language ones. Such a finding could not have been drawn from previous research, where both dominance categories had actually been merged; the dominance-related differences were therefore neutralized within the whole group. In addition to examining their differences, another interesting way of analysing the data is to study their covariations. It can be seen, for instance, that notwithstanding the differences stressed above, the within-language average SDDD values exhibit a high degree of covariation for all speakers in the sample. In other words, higher within-Catalan values are associated with higher within-Spanish values, and conversely. Thus, whatever the differences between the two kinds of within-language comparisons, they tend to be rather constant among speakers. This observation can be confirmed by the computation of a Bravais-Pearson correlation coefficient (Catalan group, r = 0. 9808; Spanish group, r = 0. 96627). By contrast, the association between the inter-language values and the intralanguage ones is weaker, particulaly for the Catalan dominant group (Catalandominant group: Catalan/Catalan vs. Catalan/Spanish, r = 0. 7374; Spanish/Spanish us. Catalan/Spanish, r = 0. 7454; Spanish-dominant group: Catalan/Catalan vs. Catalan/Spanish, r = 0. 9336; Spanish/Spanish vs. Spanish/ Catalan, r = 0. 9530). This weaker covariation in the Catalan-dominant speakers is due to the fact that, in this group, the differences between intralanguage and inter-language SDDD values are quite variable. The Catalan-dominant group contains some speakers with exceptional differences between their intra- and inter-language values, i.e., subjects with relatively low intralanguage values and high inter-language ones (e.g., male subjects 2 and 3, and female subjects 1 and 2).
5. Discussion As in previous research, between-language spectral differences appear to be significant: the statistical differences found above are due to systematically larger be tween-language dissimilarity values, relative to the within-language ones. However, in the current research a new source of variation emerges: when the whole sample is split by language dominance, the within-language comparisons of the SDDD indices achieve significance in both groups. It seems therefore that the within-language consistency tends to depend upon the language spoken: the significant differences in the Catalan-dominant group are attributable to greater voice consistency in Spanish, as opposed to Catalan , whereas in Spanish-dominant speakers, the significant differences are due to greater voice consistency in Catalan. Thus , there is a tendency towards greater voice quality variability for a given speaker in his or her dominant language, while the degree of voice coherence tends to be higher in the non-dominant language. Our covariation analyses, moreover, pointed out differences between the two groups under study, i.e., the Spanish-dominant one seems to be more homogeneous than the Catalan-dominant one. This finding requires a deeper understanding of relationships between bilingualism and voice quality variability. Very tentatively,
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one may suppose that perfectly balanced bilingual speakers exhibit similar degrees of voice consistency in each language, but large differences between their two languages; on the ot-her hand, subjects with a more marked dominance in a given language would show more between-language similarity. If this is so, our data could suggest that our Catalan-dominant sample is more heterogeneous than the Spanishdominant one, because several subjects in that sample have an unexpectedly high level of bilingualism. This could have been caused by the fact that the range of degrees of bilingualism is wider in our Catalan-dominant sample, because some speakers in this group are " more bilingual" than we expected on the basis of their written answers to the questionnaire . Distortions may have occurred , either because subjects had a wrong perception of their own usual behaviour, or because they were not used to expressing such behaviour by means of quantitative scales. Also, the relationship between proficency in a language and percentage of use may not be directly causal: particular environmental constraints may modify the ratio of linguistic activity in the two languages. For example, a better proficiency in the speaker's non-dominant language is more likely to be found if his or her non-dominant language is spoken by a larger number of people in the whole State, being at the same time its official language. 6. Conclusion
This study has investigated voice quality variability in a group of Catalan/Spanish bilinguals divided into two subgroups according to their linguistic dominance. The initial aim of the research was to assess the influence of the language spoken on the LTAS . Language effects on the long-term average spectrum have been confirmed, in agreement with the findings reported by Harmegnies & Landercy (1985) concerning French and Dutch and by Harmegnies et a!. (1989) dealing with Catalan and Spanish . The trend has been established despite the proximity of the languages under consideration , that belong to the same linguistic group. A measure of voice consistency related to the variability observed in their LTAS for each language has been established for the subjects in the chosen population . This is associated with the language dominance exhibited by each speaker. The results show a greater voice coherence in the non-dominant language, allowing more variability in the dominant one. This is to say that-at least in our experimental situation-bilingual speakers seem to be more constrained in the production of their non-dominant language. Language dominance, then, seems to be a significant variable in the characterization of the phonetic behaviour of speakers using more than one language . Further statistical treatment has revealed differences between dominance groups that might be explained in terms of different degrees of bilingualism between the subjects classified in the same subgroup. This is the case of the Catalan-dominant population. This finding may be explained by considering the socio-political characteristics of the two-languages in the Spanish State. Finally, measuring the LTAS variability in order to assess the degree of bilingualism appears to be quite a promising approach. It is also necessary to find some other tools to assess the degree of bilingualism of our subjects. Although self-assessment has been widely used in previous studies on bilingualism, several authors have shown that sometimes this is not a completely
Voice quality and bilingualism
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accurate manner of establishing language dominance. Complementary testing methods are being developed to better characterize the linguistic profile of the peakers, taking into account both phonetic and socio-linguistic parameters . The main aim of this paper was to decide whether the language spoken by an individual can act as a source of his or her voice quality variability. As to our bilingual Catalan/Spanish population, that seems to be the case; at least, long-term spectra clearly appear to be influenced. Since the validity of LT AS as a tool for the assessment of voice quality has been established in several different ways (see the Introduction), it seems rather likely that the observed phenomena were truly voice quality variations. In order to give this assertion a firmer basis, it is nevertheless important to discuss, on the one hand, whether artifactual phenomena could have influenced the observations and, on the other hand, whether other explanations of the observed phenomena can be proposed. One might believe that differences between the languages' phoneme inventories are responsible for a part of the LTAS between-language variability. We do not think that this was a major source of variation in our experiment. First, Catalan and Spanish share a large number of phonetic segments, and no spectacular differences between the two languages could be found. Second, previous research focussing on other languages (Harmegnies, 1988a) has shown, as a general rule, that corpusinduced LT AS variability, though existing, is not very big. Moreover, preliminary results involving the same languages and the same degrees of linguistic proficiency as those studied in this paper confirm that the observed between-languages differences are still obvious even when the between-language differences have been neutralized or the within-language differences have been maximized in the corpus, (Harmegnies, Bruyninckx, Llisterri & Poch, 1991). Moreover, even if differences between inventories had biased our results, they would have exposed all the subjects to the same amount of error, and should therefore not have distorted the betweenindividual and between-group contrasts. Finally, as Bruyninckx & Harmegnies (1990) and Harmegnies & Poch (1992) suggested, both on the basis both of speculative reasoning and analysis of previous research (Nolan, 1983; Esling, 1983; Esling & Dickson, 1985; de Boysson-Bardies, Sagart, Halle & Durand, 1986; among others), we think that the reasons for the between-language LT AS variability are properly to be found in voice quality shifts due to variation in the dominant features of articulatory behaviours. This obviously remains to be tested by means of specific methodology, out of the range of the present experiment. The authors are grateful to Professor M. Beckman for her useful comments on the manuscript and her editorial assistance, and also to Professor A . Landercy for his advice during the development of the project.
References Abercrombie, D . (1967) Elements of general phonetics. Edinburgh: Edinburgh University Press . Banus-Terol, V . (1971) Weighted average spectrum of human speech: an approach, Proceedings of the 7th International Congress on Acoustics, 253-256. Boullosa, R. R. & Perez Ruiz, S. J . (1984) Long-term average spectrum of Spanish, Applied Acoustics, 17, 201-208. de Boysson-Bardies, B., Sagart, L., Halle, P. & Durand. D. (1986) Acoustic investigations of cross-linguistic variability in babling. In Precursors of early speech (B. Lindblom & R. Zetterstrom , editors), pp. 113-126. Southampton: Stokton.
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Bruyninckx, M. & Harmegnies, B. (1990) Note sur les invariants spectraux imputables aux langues et leurs repercussions en didactique , Actes du col/oque " Le franrais et le developpement", Vancouver, 195-211.. Dejonckheere, P. H. (1984) Comparison between long-time average-spectra of the voice and the sonagraphic degree of hoarseness according to Yanagihara's classification, International Journal of Rehabilitation Research, 7, 73-74. Esling , J. H. (1983) Quantitative analysis of acoustic correlates of supralaryngeal voice quality features in the long time spectrum , Proceedings of the lOth International Congress of the Phonetic Sciences, Utrecht, 363. Esling, J. H. & Dickson, C. (1985). Acoustical procedures for articulatory setting analysis accent. In Papers from the 5th International Conference on Methods in Dialectology (H. J. Warkentyne , editor). Victoria: University of Victoria. Finck, C. & Harmegnies, B. (1994) A versatile, voice quality based procedure for the assessment of phonatory evolution, Acts of the 1st /CPLA Symposium. Cardiff: Benjamins series. Formby, C. & Monsen , R. B. (1982) Long-term speech spectra for normal and hearing-impaired adolescents , Journal of the Acoustical Society of America, 71, 196-202. Fritzell, B., Hallen , 0. & Sundberg, J . ( 1974) Evaluation of teflon injection procedures for paralytic dysphonia, Folia Phoniatrica , 26, 414-421. Frokjaer-Jensen , B. & Prytz, S. (1976) Registration of voice quality, BruiH & Kjaer Technical Review, 3 , 3-17. Furui, S. , Itakura , F. & Saito , S. (1972) Talker recognition considering the variation of long-time average spectrum , Trans. IECE, 55-A, 10, 550. Furui , S. , Itakura , F. & Saito , S. (1975) Personal information in the long time average speech spectrum, The Electrical Communication Laboratories, 23 , 9-10. Gubrynowicz, R. (1971) Methode d 'analyse statistique du spectre de Ia parole : Application a Ia reconnaissance automatique du locuteur, Proceedings of the 7th International Congress on Acoustics, 3, 25-28. Harmegnies, B. ( 1988a) Contribution a Ia caracterisation de Ia qualite vocale ; analyses plurielles de spectres moyen.~ a long terme de parole, Doctoral Dissertation, Universite de Mons. Harmegnies , B. ( 1988b) A new dissimilarity index for the comparison of speech spectra, Pattern Recognition Letters, 8, 153-158. Harmegnies, B. , Bruyninckx, M. , Llisterri , J. & Poch , D. (1989) Effects of language change on voice quality. An experimental contribution to the study of the Catalan-Castillian case, Proceedings of the 1st European Conference on Speech Communication and Technology, Paris, 489-492. Harm egni es. B., Bruyninckx , M., Llisterri , J. & Poch, D. ( 1991) Effects of language change in voice qualit y in bilingual speakers, Proceedings of the 2nd European Conference on Speech Communication and Technology , Genova, 1, 165-168. Harm egni es, B. & Landercy, A. (1985) Language features in the long-term average spectrum, Revue de Phonetique Appliquee, 73-75 , 69- 80. Harmegnies, B., Landercy, A. & Bruyninckx, M. (1987) An experiment in inter-languages speaker recognition using the SDDD index , Proceedings of the lith International Congress of Phonetic Sciences, Tallinn , 241-244. Harmegnies , B. & Poch , D. (1992) Fausse science et marketing linguistique, Actes du Congres "Enseignement des langues etrangeres: recherche et pratique, vers une convergence?", Revue de Phonetique Appliquee, 103-104, 211-217. Hollien, H. & Majewski, M. ( 1977) Speaker identification by long-term spectra under normal and distorted speech conditions , Journal of the Acoustical Society of America , 62, 975-980. Laver, J. (1980) The phonetic description of voice quality. Cambridge: Cambridge University Press. Lorand, P., Minier, G. & Saliou , A. (1975) Determination du spectre a long terme de Ia parole (langue fran<;aise), Recherches en Acoustique, CNET, II, 15-25. Majewski, W. & Hollien , H. ( 1974) Speaker identification by means of long-term speech spectra, 8th International Congress on Acoustics, London, 274. Majewski, W. & Hollien , H. (1975) Euclidean distances between long term spectra as a criterion for speaker identification. In Speech communication , Vol. 3, (G . Fant, editor), pp. 303-310. Stockholm: Almqvist and Wiksell. Navarro Tomas, T. (1946). Escalade frecuencia de los fonemas espaiioles . In £studios de fonologia espanola. pp. 15-30. New York: Las Americas Publishing Company. Nolan, F. (1983) The phonetic bases of speaker recognition. Cambridge: Cambridge University Press. Plant, G. (1983) The effects of an acquired profound hearing loss on speech production, British Journal of Audiology, 18, 39-48. Rafel, J. (1979) Dades sobre Ia freqiiencia de les unitats fonologiques en catala, Estudis Universitaris Catalans, 23, 473-496. Ramishvili, G. S. (1970) Some problems in automatic identification of spoken utterances and speakers, Speech Transmission Laboratory Quaterly Progress and Status Report, 2, 36.
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31
Ta rn6czy, T . (1958) Determination du spectre de Ia parole avec une methode nouvelle , Acustica, 8 , 392-395 . Ta rn 6czy , T . (1962) Sprachliche verschiede n erhalten durch spechhormethode , 4th International Congress on A coustics, Copenhagen , 627, 1-4. Tosi. 0. (1979) Voice identification: theory and legal applications. Baltimore: University Park Press. \ "iladot, M. A. (1981) El bilingiiisme a Catalunya. lnvestigaci6 i psicologia. Barcelona : Laia. Weinberg, 8. , Horii , Y. & Smith , B. (1980) Long--time spectral and intensity characteristics of oesoph ageal speech, Journal of the Acoustical Society America , 67, 1781-1784. Za lewski , J., Majewski , W. & Hollien , H . (1975) Cross-correlation of long-te rm speech spectra as a speaker identification technique , Acustica, 34, 20-24 .
Appendix
Catalan text El barri de xalets de Sitges era un Hoc on m'agradava d'anar a passejar a omenc;aments de temporada. I Ia platja era el lloc on feiem Ia primera cabussada de Ia temporada amb les noies del pis. No ens agradava tant com les platges de \f allorca pen) de tots els llocs de Ia costa baixa proxima a Barcelona era el mes passador. Els mallorquins sempre trobem a faltar Ia nostra terra que jutgem millor. \1 es endavant elles se n'anaven a l'illa a passar l'estiu i jo tornava a banyar-m'hi se mpre que podia. Ara ja feia dotze anys que no hi havia vingut. { ~I
bari
d~
f ~lets d~ sid3 er~ un A.;,k on m~gr~dab~ d~na ;} p;}S;}3a ;} kum;}fiS;}mens de
~ m purad~
i le plad3~ er~ ~I A.;-,k on fci~m Jg primer~ k~busad~ dg Jg t~mpurade gm l;u nJ~z dgl pis no ~nz ~gr~dabg tan bm les plad3~z de mgA.;-,rb peo d~ tots ~lz .b kz d~ I~ bstg af d pDksimg g b~rs~long er~ gl mes pgs~do dlz m;:Ji\urkins semprg trubcm ~ f~lta Jg n;-,stre tcr~ k~ 3ud3cm miA.o mez ;:Jnd~ban ei\gs s~ ngnabgn g lii\g ~ pgsa l~stiu i 3;, turnabe ~ b~parmi sempr~ b pudid ar;:) ia fcig dodzd ;J]1S b no i ;Jbi~ bil)gut]
Spanish text El joyero Federico Vanero ha sido condenado porIa Audiencia de Santander a ocho meses de arresto mayor y cincuenta mil pesetas de multa por un delito de compra de objetos robados. La vistra oral se celebr6 el miercoles pasado y, durante ella, uno de los fiscales, Carlos Valcarcel, pidi6 para el joyero tres afios de prisi6n menor y una multa de cincuenta mil pesetas. Gracias a las revelacinoes de Vanero de hace dos afios y media se lleg6 a descubrir Ia existencia de una sospechosa mafia policial en Espana, parte de Ia cual se vio envuelta en el llamado " caso El Nani". {el xoj.ero federiko banero a sido kondenado por Ia audien9ia de santander a otfo meses de aresto maior i 9inkuenta mil pesetas de multa por un delito de kompra de obxetos robados Ia bista oral se 9elebro el mierkoles pasado i durante eA.a uno de los fiskales karlos alk ar9el pidio para al xoj.ero tres apos de prision menor i una multa de 9inkuenta mil pesetas . == ra9ias a las rebela9iones de banero de aee dos apos i medio se A.ego a deskubrir Ia egsisten9ia de una sospetfosa mafia poli9ial en espapa parte de Ia kual se bj.o em buelta en el A.amado kaso el nani]
Language-induced voice quality variability in bilinguals Marielle Bruyninckx and Bernard Harmegnies Service de Ia communication parlee, Universite de Mons-Hainaut, B-7000 Mons, Belgium
Joaquim Llisterri and Dolors Poch-Oiive Departament de Filologia Espanyola, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Spain Received 22nd May 1991, and in revised form 8th February 1993
The paper examines whether the language spoken exerts influences on a speaker's voice quality. Bilingual (Catalan/Spanish) subjects were studied in order to neutralize the speakers individual characteristics. The Long Term Average Spectrum (LTAS) was used as an acoustical measure of voice quality. The sample of 12 males and 12 females was divided into two categories of linguistic dominance (Catalan and Spanish dominances). Each subject produced five repetitions each of a Spanish and a Catalan phonetically balanced text. A 400-line LT AS was computed for each repetition; the 240 spectra so obtained were compared by means of a pattern recognition procedure (SDDD dissimilarity index). Within-speaker comparisons of two kinds were performed: the between-language (Catalan/Spanish) and the within-language (Catalan/Catalan and Spanish/Spanish) ones. The between-language variability was higher than the within-language variability, irrespective of the sex and language dominance categories. The data, moreover, exhibited a tendency towards greater within-language variability in the dominant language than in the non-dominant one. Finally, a greater correlation in the Catalan dominant group between intra- and inter-language LT AS dissimilarities suggests differences in the mastery of the second language between the two dominance groups.
1. Introduction
Many experimenters involved in acoustical analysis of voice quality have based their works upon the use of Long Term Average Spectra (LT AS). Both theoretical and empirical reasons seem to plead for their choice. On the one hand, remembering the definition that Abercrombie (1967:91) gave for the concept of voice quality ("[voice quality] is a quasi-permanent quality running through all the sound that issues from his [the speaker's] mouth") , it seems quite reasonable to apply an averaging process to speech samples in order to peutralize the short-term segment characteristics and thus collect phoneme-independent speaker-dependant information. This is definitely the purpose of long-term spectra, which are made of instantaneous spectra averaged over a sample of speech "long enough for the effect of individual linguistic segments 0095-4470/94/010019 + 13 $08.00/0
©
1994 Academic Press Limited
20
M. Bruyninckx et al.
no longer to be significant" (Nolan, 1983:130). On the other hand, many experiments have established the validity of the LT AS taken as an acoustical cue to the speaker's identity, mainly in the field of speaker recognition (Ramishvili, 1970; Gubrynowicz, 1971; Furui, ltakura & Saito, 1972, 1975; Majewski & Hollien, 1974; Zalewski, Majewski & Hollien, 1975; etc.). Experiments dealing with abnormal voices have, moreover, proved its sensitivity to special phonation types (e.g., in deaf subjects, Formby & Monsen, 1982; Plant, 1983; esophageal voices, Weinberg, Horii & Smith, 1980; voice after surgery , Fritzell, Hallen & Sundberg, 1974; Finck & Harmegnies, forthcoming). Other experiments (Nolan, 1983; Harmegnies, Bruyninckx , Llisterri & Poch, 1989) have also shown important correlations between LTAS variations and the use of specific "settings" as described by Laver (1980). The long-term spectrum therefore appears as a promising tool for the study of voice quality , or at least for substantial aspects of it. Among the determinants of voice quality, variables such as the speaker's sex, age, emotional state and social origin, have received special attention. Whether the language spoken should be considered or not as a supplementary source of the voice quality variability is nevertheless still an open debate. Most experiments dealing with this topic have focused on the popular conception that languages could be characterized each by specific overall spectral tendencies. However, no precise conclusion can be drawn from these works. Some authors have reported significant effects of the language spoken by a given speech community on the long-term spectral features of individual speakers (Tarn6czy, 1958, 1962; Banuls-Terol, 1971; etc.), while others failed to find a correlation between these factors (Lorand, Minier & Saliou, 1975; Boullosa & Perez Ruiz, 1984; etc.) . The consistency of the results obtained in the field of speaker recognition is no greater, since different experiments dealing with various languages have led to apparently contradictory results. In this respect, Nolan (1983) emphasizes the apparent conflict between Tosi 's (1979) results showing a relative invariance in the long-term average spectrum (LTAS) for a given speaker and Majewski & Hollien's (1975), suggesting a language effect on the speaker's LT AS. Harmegnies & Landercy (1985) have reviewed the descriptive research in the field of voice quality, showing the lack of efficient ways of quantifying the observed variability. They have also suggested that, in some cases, at least part of the assumed language effects reported might be attributed to intrinsic individual variability. They therefore focused on bilingual speakers (French/Dutch), in order to neutralize it. A mixed quantitative/qualitative methodology has been developed, allowing careful examination of the differences between languages, notwithstanding the speaker-related variability. The results confirmed the existence of a significant language-related component of long-term spectral variability, but also revealed that language effects are smaller than individual effects (Harmegnies & Landercy, 1985; Harmegnies, Landercy and Bruyninckx, 1987). These findings make it possible to understand some of the reasons for the apparently contradictory conclusions in previously published experiments , but they also show the need for applying the same methodology to other languages. In this paper we will report on our joint research concerning differences in long-term spectral features related to the use of Castillian Spanish as opposed to Catalan in bilingual speakers of these languages.
Voice quality and bilingualism
21
2. Sociolinguistic background We will refer in this study to subjects living in the area of Barcelona (Catalonia, Spain). Catalan and Spanish are the official languages of the autonomous community of Catalonia; they are both taught at school and used in the media and in everyday communication. Both monolingual and bilingual speakers are found among the population of Catalonia. Catalan monolingualism is a very unlikely possibility, due to the official character of Spanish in Spain. Monolingual Spanish speakers are mainly to be found among recently arrived immigrants to Catalonia. They may be speakers of any variety of peninsular Spanish. Bilingual subjects range from native Catalan speakers who know standard Spanish (which is the official language of the whole State) to native Spanish speakers with different dialectal backgrounds who have acquired Catalan as a second language, with greater or lesser proficiency. Due to those socio-linguistic factors, most bilingual speakers in Catalonia therefore exhibit either Catalan or Spanish dominance. This paper will focus on subjects with a fairly equal knowledge of both languages, but showing a degree of language dominance either in Catalan or in Spanish .
3. Experiment 3.1. Selection of subjects The choice of speakers was made according to answers to a written questionnaire, introduced by Viladot (1981), administered to a large group of first year university students at the Universitat Autonoma de Barcelona. The questions addressed their use of Catalan and Spanish in four different skills: listening, speaking, reading and writing. Subjects had to give a subjective percentage figure representing their use of each language in a series of specific environments or situations (at home, with friends, at the University, at work, in everyday activities in town, communicating with the Administration, etc.) . This gave an estimate of their patterns of language use for each activity related to the above-mentioned skills. Questions about geographical origins and language background in the family have also been included. A sample of 24 bilingual subjects has been retained for the present study . They are all bilingual, but their use of Catalan and Spanish exhibits different tendencies: in half of the group the percentage of use is at least 60% for Catalan, and at most 40 % for Spanish in at least two-thirds of the situations examined for each skill-those being the Catalan-dominant subjects; the other half, the Spanishdominant speakers, shows the opposite linguistic behaviour. Spanish-dominant subjects are all users of standard peninsular Spanish . Moreover, since the degree of LT AS variability has turned out to be sex-dependent (Harmegnies, 1988a ), both male and female subjects were recorded. The population studied then is as follows : six male and six female bilinguals with Catalan dominance, and six male and six female bilinguals with Spanish dominance. 3.2. Corpus A phonetically balanced text was prepared for each language (see the Appendix) following the phonetic distribution reported for Catalan by Rafel (1979) and for
M. Bruyninckx et al.
22
Spanish by Navarro Tomas (1946). The Catalan corpus consisted of 177 vowels and 210 consonants with a total of 387 phonological units, whereas the Spanish one consisted of 209 vowels and 231 consonants, yielding a total of 440 units. Figure 1 compares the distribution of phonemes in the text with their general distribution in both languages. The texts lasted for about 20 s and were read at the speaker's natural rate.
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Figure 1. Observed and expected frequencies of the phonemes in the (a) Catalan corpus and (b) Spanish corpus.
Voice quality and bilingualism
23
3. 3. Experimental setting Five repetitions of each text were recorded for each subject. The recordings took place in a sound-proof room, with the speakers sitting in front of a microphone placed at a constant distance of 20 em from the mouth. A Revox A 77 tape recorder and a Sennheiser MD 441N cardioid microphone were used. 3.4. Acoustical analysis The procedure we used to compute our LTAS is of the same type as those used in classicallitterature about long-term spectra (Furui et al., 1975; Zalewski et al., 1975; Hollien & Majewski, 1977; etc .), i.e., it allows straightforward averaging of the whole portion of signal taken into account, notwithstanding the kind of segments contained in it. The built-in so-called "linear" averaging procedure of a Briiel & Kjaer 2033 analyser was selected for that purpose . This device, which was previously used by several experimenters (Frokjaer-Jensen & Prytz, 1976; Boullosa & Perez Ruiz, 1984; Dejonckheere, 1984; etc.) is based upon a converging algorithm which allows real-time averaging of the input signal, and thus does not require that the signal duration be known in advance. It is therefore possible to interrupt the averaging process at any time , on the basis of aural control of the input signal (e.g., in order to reject noisy segments , or unexpected repetitions of words, etc.) In the case of the present experiment, averaging was stopped just after the end of each corpus utterance. This procedure ensures invariance of the speech material accounted for by all the LTAS across utterances, speakers and groups in each language. This was not achieved in experiments by other authors where the integrating time was held constant, leaving room for corpus-induced variability. 3. 5. Comparison procedure
3. 5.1. Dissimilarity measure For the purpose of assessing language-induced effects on the long-term spectrum, a quantitative methodology has been used . Comparisons of the shapes of the LT AS were performed by means of a pattern-matching measure, the SDDD index (Harmegnies, 1988b ), defined as follows : p ,u .. r/'lt,r r-_rv ~~-' {d!r 1 k L£,YV' ~ 1"""\ , SDDDss' = - ~ (S;- Sf- M") 2 iY ~~.ff:._(Ji)_
~
K; = I
0-
"<;;
where S and S' are the spectra being compared, each one defined by its s; and sf level values for each of the k frequency components, and M" is the mean for the S;- Sf differences. As equation (1) shows, SDDD is the Standard Deviation of the Differences Distribution. If the shapes of the spectra compared are highly similar, the S;- Sf differences deliver values that vary little across the frequency components and the standard deviation is therefore small. If the shapes are different , large level differences can be found in certain frequency channels, and small ones in others and the standard deviation of the S;- Sf differences therefore increases. Hence SDDD is a dissimilarity index: high SDDD values indicate considerable dissimilarity between spectra. Moreover, being insensitive to variations in the overall levels of the
M. Bruyninckx et al. compared spectra, SDDD does not need any intensity normalization prior to the computation. 3.5.2. Comparison types Two types of within-speaker comparisons of the stored LT AS were performed for each subject: between-language comparisons and within-language comparisons. In the case of the between-language comparisons (Catalan vs. Spanish), each Catalan LT AS of each subject was matched against each Spanish LTAS of the same subject; this procedure resulted in 600 between-language/within-speaker comparisons (25 comparisons x 2 dominance groups x 2 sexes x 6 subjects). For the within-language matchings (i.e ., Catalan vs. Catalan , and Spanish vs. Spanish), one comparison was performed for each possible non-redundant pair of the five LTAS in each language for each one of the 24 speakers, i.e., 10 comparisons by subject and by language, thus 480 within-speaker comparisons for the whole sample (2 languages x 2 sexes x 6 subjects x 10 matchings x 2 dominance groups). Thus, a total of 1080 comparisons have been performed altogether. 4. Results
An exhaustive presentation of the whole set of 1080 dissimilarity values being impossible, the results of the comparison procedure described above have been summarized . They are shown in Fig. 2, where lowest and highest values, together with means and standard deviations of the SDDD index , have been plotted for each subject and each comparison condition. Overall statistics are given in Table I for each comparison condition in each sex/language dominance subgroup of six speakers. It can be easily seen from Figs 2(a)-(d) that the SDDD values drawn from within-language comparisons exhibit the same tendencies as reported by Harmegnies (1988a ), on the occasion of within-language comparisons of various French LTAS: the average SDDD values score around 2.5 for men and 3.2 for women . As usual , the data show a considerable amount of between-speaker variability: the individual average SDDD values vary from 1.93 to 4.43 for Catalan vs . Catalan, from 1.83 to 4.59 for Spanish vs. Spanish , and from 2.41 to 5.03 for Catalan vs. Spanish. An examination of the groups' central tendencies shows that the SDDD index values derived from between-language comparisons tend to score higher than those drawn from within-language matchings. This relationship can be observed in Table I for the average values in each sex/dominance group . This tendency appears moreover to be very strong, since the relationship holds true for each one of the 24 speakers in the sample (see Fig. 2 where the third bar consistently shows the largest mean). Although the language effect appeared rather obvious on the basis of this simple descriptive study of the results , we nevertheless decided to confirm its significance by inferential means. For that purpose , we considered the average SDDD for each subject in each comparison condition as an overall measure of his or her voice quality variability. Our hypothesis was that the speakers would exhibit a greater voice consistency intralingually than inter-lingually (i .e ., their between-language
Voice quality and bilingualism
25
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Figure 2. Bar graph showing means ± standard deviation, and lower and upper values for each comparison condition (for each subject, the order of bars from top to bottom is: CAT/CAT, SPAN/SPAN, CAT/SPAN). (a) Catalan-dominant males; (b) Catalan-dominant females ; (c) Spanish-dominant males; and (d) Spanish-dominant females.
26
M. Bruyninckx et al. TABLE I. Grand means of the SDDD values for each language dominance/sex subgroups in each comparison condition
Catalan vs. Catalan
Castilian vs. Castilian
Catalan vs. Castilian
Catalan Males Females Castilian Males Females
2.34 3.27
2.08 3.24
3.11 4.00
2.54 3.04
2.58 3.35
2.98 3.80
All
2.80
2.81
3.47
voice quality variability would be significantly greater than their within-language one). We first applied the treatment as in our previous research (Harmegnies et al., 1989). In that experiment, a homogeneous group of bilingual subjects was studied so that language dominance and sex did not vary. Three comparison conditions were established as in the present study: Catalan/Catalan, Spanish/Spanish and Catalan/Spanish. An overall comparison of these three conditions revealed a significant between-conditions effect; nevertheless, once the between-language (Catalan/Spanish) comparisons were removed, the same processing resulted in a lack of significance. Thus, according to this study, the between-condition differences were attributed to between-language differences only. In order to reproduce the treatment with our new data, we performed a one-way non-parametric Friedman analysis of variance performed on the whole group of 24 subjects , disregarding dominance and sex category. The three data sets under analysis consisted of average SDDD values drawn from the three comparison conditions (within-language Catalan; within-language Spanish; between-language). As in previous research, there was a significant effect of comparison condition (Friedman analysis of variance: chi-square= 6, df = 2, p < 0.001). As the difference between the first two comparison conditions (i.e., both within-language) is very small (overall averages are , respectively, 2.80 and 2.81) and not significant at all (Wilcoxon test , p = 0.8864), it appears very clearly that the overall effect of condition is due to differences between the intralanguage and the inter-language values. The analyses thus confirm our earlier results. A closer examination of the results, taking into account the subjects' linguistic dominance, nevertheless suggests the existence of sources of variability that were not observed previously . Table I shows that in Catalan dominant speakers, the CAT /CAT SDDD values tend to score higher than the SPAN /SPAN ones, and the opposite relationship can be observed in Spanish dominant subjects . This informal observation was tested by inferential analysis: the whole sample was split by language dominance (i .e., we made two groups of 12 speakers , with the same language dominance in each group), and we performed again inferential tests aimed at comparing the two within-language comparison conditions. This revealed significant differences between the two
Voice quality and bilingualism
27
within-language comparison conditions in both language groups (Wilcoxon test, Catalan-dominant group: p = 0.0499; Wilcoxon test, Spanish-dominant group: p = 0.0499). These results therefore could suggest a new idea: voice consistency in bilinguals is greater in the non-dominant language; between-language variability is nevertheless greater than within-language ones. Such a finding could not have been drawn from previous research, where both dominance categories had actually been merged; the dominance-related differences were therefore neutralized within the whole group. In addition to examining their differences, another interesting way of analysing the data is to study their covariations. It can be seen, for instance, that notwithstanding the differences stressed above, the within-language average SDDD values exhibit a high degree of covariation for all speakers in the sample. In other words, higher within-Catalan values are associated with higher within-Spanish values, and conversely. Thus, whatever the differences between the two kinds of within-language comparisons, they tend to be rather constant among speakers. This observation can be confirmed by the computation of a Bravais-Pearson correlation coefficient (Catalan group, r = 0. 9808; Spanish group, r = 0. 96627). By contrast, the association between the inter-language values and the intralanguage ones is weaker, particulaly for the Catalan dominant group (Catalandominant group: Catalan/Catalan vs. Catalan/Spanish, r = 0. 7374; Spanish/Spanish us. Catalan/Spanish, r = 0. 7454; Spanish-dominant group: Catalan/Catalan vs. Catalan/Spanish, r = 0. 9336; Spanish/Spanish vs. Spanish/ Catalan, r = 0. 9530). This weaker covariation in the Catalan-dominant speakers is due to the fact that, in this group, the differences between intralanguage and inter-language SDDD values are quite variable. The Catalan-dominant group contains some speakers with exceptional differences between their intra- and inter-language values, i.e., subjects with relatively low intralanguage values and high inter-language ones (e.g., male subjects 2 and 3, and female subjects 1 and 2).
5. Discussion As in previous research, between-language spectral differences appear to be significant: the statistical differences found above are due to systematically larger be tween-language dissimilarity values, relative to the within-language ones. However, in the current research a new source of variation emerges: when the whole sample is split by language dominance, the within-language comparisons of the SDDD indices achieve significance in both groups. It seems therefore that the within-language consistency tends to depend upon the language spoken: the significant differences in the Catalan-dominant group are attributable to greater voice consistency in Spanish, as opposed to Catalan , whereas in Spanish-dominant speakers, the significant differences are due to greater voice consistency in Catalan. Thus , there is a tendency towards greater voice quality variability for a given speaker in his or her dominant language, while the degree of voice coherence tends to be higher in the non-dominant language. Our covariation analyses, moreover, pointed out differences between the two groups under study, i.e., the Spanish-dominant one seems to be more homogeneous than the Catalan-dominant one. This finding requires a deeper understanding of relationships between bilingualism and voice quality variability. Very tentatively,
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M. Bruyninckx et al.
one may suppose that perfectly balanced bilingual speakers exhibit similar degrees of voice consistency in each language, but large differences between their two languages; on the ot-her hand, subjects with a more marked dominance in a given language would show more between-language similarity. If this is so, our data could suggest that our Catalan-dominant sample is more heterogeneous than the Spanishdominant one, because several subjects in that sample have an unexpectedly high level of bilingualism. This could have been caused by the fact that the range of degrees of bilingualism is wider in our Catalan-dominant sample, because some speakers in this group are " more bilingual" than we expected on the basis of their written answers to the questionnaire . Distortions may have occurred , either because subjects had a wrong perception of their own usual behaviour, or because they were not used to expressing such behaviour by means of quantitative scales. Also, the relationship between proficency in a language and percentage of use may not be directly causal: particular environmental constraints may modify the ratio of linguistic activity in the two languages. For example, a better proficiency in the speaker's non-dominant language is more likely to be found if his or her non-dominant language is spoken by a larger number of people in the whole State, being at the same time its official language. 6. Conclusion
This study has investigated voice quality variability in a group of Catalan/Spanish bilinguals divided into two subgroups according to their linguistic dominance. The initial aim of the research was to assess the influence of the language spoken on the LTAS . Language effects on the long-term average spectrum have been confirmed, in agreement with the findings reported by Harmegnies & Landercy (1985) concerning French and Dutch and by Harmegnies et a!. (1989) dealing with Catalan and Spanish . The trend has been established despite the proximity of the languages under consideration , that belong to the same linguistic group. A measure of voice consistency related to the variability observed in their LTAS for each language has been established for the subjects in the chosen population . This is associated with the language dominance exhibited by each speaker. The results show a greater voice coherence in the non-dominant language, allowing more variability in the dominant one. This is to say that-at least in our experimental situation-bilingual speakers seem to be more constrained in the production of their non-dominant language. Language dominance, then, seems to be a significant variable in the characterization of the phonetic behaviour of speakers using more than one language . Further statistical treatment has revealed differences between dominance groups that might be explained in terms of different degrees of bilingualism between the subjects classified in the same subgroup. This is the case of the Catalan-dominant population. This finding may be explained by considering the socio-political characteristics of the two-languages in the Spanish State. Finally, measuring the LTAS variability in order to assess the degree of bilingualism appears to be quite a promising approach. It is also necessary to find some other tools to assess the degree of bilingualism of our subjects. Although self-assessment has been widely used in previous studies on bilingualism, several authors have shown that sometimes this is not a completely
Voice quality and bilingualism
29
accurate manner of establishing language dominance. Complementary testing methods are being developed to better characterize the linguistic profile of the peakers, taking into account both phonetic and socio-linguistic parameters . The main aim of this paper was to decide whether the language spoken by an individual can act as a source of his or her voice quality variability. As to our bilingual Catalan/Spanish population, that seems to be the case; at least, long-term spectra clearly appear to be influenced. Since the validity of LT AS as a tool for the assessment of voice quality has been established in several different ways (see the Introduction), it seems rather likely that the observed phenomena were truly voice quality variations. In order to give this assertion a firmer basis, it is nevertheless important to discuss, on the one hand, whether artifactual phenomena could have influenced the observations and, on the other hand, whether other explanations of the observed phenomena can be proposed. One might believe that differences between the languages' phoneme inventories are responsible for a part of the LTAS between-language variability. We do not think that this was a major source of variation in our experiment. First, Catalan and Spanish share a large number of phonetic segments, and no spectacular differences between the two languages could be found. Second, previous research focussing on other languages (Harmegnies, 1988a) has shown, as a general rule, that corpusinduced LT AS variability, though existing, is not very big. Moreover, preliminary results involving the same languages and the same degrees of linguistic proficiency as those studied in this paper confirm that the observed between-languages differences are still obvious even when the between-language differences have been neutralized or the within-language differences have been maximized in the corpus, (Harmegnies, Bruyninckx, Llisterri & Poch, 1991). Moreover, even if differences between inventories had biased our results, they would have exposed all the subjects to the same amount of error, and should therefore not have distorted the betweenindividual and between-group contrasts. Finally, as Bruyninckx & Harmegnies (1990) and Harmegnies & Poch (1992) suggested, both on the basis both of speculative reasoning and analysis of previous research (Nolan, 1983; Esling, 1983; Esling & Dickson, 1985; de Boysson-Bardies, Sagart, Halle & Durand, 1986; among others), we think that the reasons for the between-language LT AS variability are properly to be found in voice quality shifts due to variation in the dominant features of articulatory behaviours. This obviously remains to be tested by means of specific methodology, out of the range of the present experiment. The authors are grateful to Professor M. Beckman for her useful comments on the manuscript and her editorial assistance, and also to Professor A . Landercy for his advice during the development of the project.
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Bruyninckx, M. & Harmegnies, B. (1990) Note sur les invariants spectraux imputables aux langues et leurs repercussions en didactique , Actes du col/oque " Le franrais et le developpement", Vancouver, 195-211.. Dejonckheere, P. H. (1984) Comparison between long-time average-spectra of the voice and the sonagraphic degree of hoarseness according to Yanagihara's classification, International Journal of Rehabilitation Research, 7, 73-74. Esling , J. H. (1983) Quantitative analysis of acoustic correlates of supralaryngeal voice quality features in the long time spectrum , Proceedings of the lOth International Congress of the Phonetic Sciences, Utrecht, 363. Esling, J. H. & Dickson, C. (1985). Acoustical procedures for articulatory setting analysis accent. In Papers from the 5th International Conference on Methods in Dialectology (H. J. Warkentyne , editor). Victoria: University of Victoria. Finck, C. & Harmegnies, B. (1994) A versatile, voice quality based procedure for the assessment of phonatory evolution, Acts of the 1st /CPLA Symposium. Cardiff: Benjamins series. Formby, C. & Monsen , R. B. (1982) Long-term speech spectra for normal and hearing-impaired adolescents , Journal of the Acoustical Society of America, 71, 196-202. Fritzell, B., Hallen , 0. & Sundberg, J . ( 1974) Evaluation of teflon injection procedures for paralytic dysphonia, Folia Phoniatrica , 26, 414-421. Frokjaer-Jensen , B. & Prytz, S. (1976) Registration of voice quality, BruiH & Kjaer Technical Review, 3 , 3-17. Furui, S. , Itakura , F. & Saito , S. (1972) Talker recognition considering the variation of long-time average spectrum , Trans. IECE, 55-A, 10, 550. Furui , S. , Itakura , F. & Saito , S. (1975) Personal information in the long time average speech spectrum, The Electrical Communication Laboratories, 23 , 9-10. Gubrynowicz, R. (1971) Methode d 'analyse statistique du spectre de Ia parole : Application a Ia reconnaissance automatique du locuteur, Proceedings of the 7th International Congress on Acoustics, 3, 25-28. Harmegnies, B. ( 1988a) Contribution a Ia caracterisation de Ia qualite vocale ; analyses plurielles de spectres moyen.~ a long terme de parole, Doctoral Dissertation, Universite de Mons. Harmegnies , B. ( 1988b) A new dissimilarity index for the comparison of speech spectra, Pattern Recognition Letters, 8, 153-158. Harmegnies, B. , Bruyninckx, M. , Llisterri , J. & Poch , D. (1989) Effects of language change on voice quality. An experimental contribution to the study of the Catalan-Castillian case, Proceedings of the 1st European Conference on Speech Communication and Technology, Paris, 489-492. Harm egni es. B., Bruyninckx , M., Llisterri , J. & Poch, D. ( 1991) Effects of language change in voice qualit y in bilingual speakers, Proceedings of the 2nd European Conference on Speech Communication and Technology , Genova, 1, 165-168. Harm egni es, B. & Landercy, A. (1985) Language features in the long-term average spectrum, Revue de Phonetique Appliquee, 73-75 , 69- 80. Harmegnies, B., Landercy, A. & Bruyninckx, M. (1987) An experiment in inter-languages speaker recognition using the SDDD index , Proceedings of the lith International Congress of Phonetic Sciences, Tallinn , 241-244. Harmegnies , B. & Poch , D. (1992) Fausse science et marketing linguistique, Actes du Congres "Enseignement des langues etrangeres: recherche et pratique, vers une convergence?", Revue de Phonetique Appliquee, 103-104, 211-217. Hollien, H. & Majewski, M. ( 1977) Speaker identification by long-term spectra under normal and distorted speech conditions , Journal of the Acoustical Society of America , 62, 975-980. Laver, J. (1980) The phonetic description of voice quality. Cambridge: Cambridge University Press. Lorand, P., Minier, G. & Saliou , A. (1975) Determination du spectre a long terme de Ia parole (langue fran<;aise), Recherches en Acoustique, CNET, II, 15-25. Majewski, W. & Hollien , H. ( 1974) Speaker identification by means of long-term speech spectra, 8th International Congress on Acoustics, London, 274. Majewski, W. & Hollien , H. (1975) Euclidean distances between long term spectra as a criterion for speaker identification. In Speech communication , Vol. 3, (G . Fant, editor), pp. 303-310. Stockholm: Almqvist and Wiksell. Navarro Tomas, T. (1946). Escalade frecuencia de los fonemas espaiioles . In £studios de fonologia espanola. pp. 15-30. New York: Las Americas Publishing Company. Nolan, F. (1983) The phonetic bases of speaker recognition. Cambridge: Cambridge University Press. Plant, G. (1983) The effects of an acquired profound hearing loss on speech production, British Journal of Audiology, 18, 39-48. Rafel, J. (1979) Dades sobre Ia freqiiencia de les unitats fonologiques en catala, Estudis Universitaris Catalans, 23, 473-496. Ramishvili, G. S. (1970) Some problems in automatic identification of spoken utterances and speakers, Speech Transmission Laboratory Quaterly Progress and Status Report, 2, 36.
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Ta rn6czy, T . (1958) Determination du spectre de Ia parole avec une methode nouvelle , Acustica, 8 , 392-395 . Ta rn 6czy , T . (1962) Sprachliche verschiede n erhalten durch spechhormethode , 4th International Congress on A coustics, Copenhagen , 627, 1-4. Tosi. 0. (1979) Voice identification: theory and legal applications. Baltimore: University Park Press. \ "iladot, M. A. (1981) El bilingiiisme a Catalunya. lnvestigaci6 i psicologia. Barcelona : Laia. Weinberg, 8. , Horii , Y. & Smith , B. (1980) Long--time spectral and intensity characteristics of oesoph ageal speech, Journal of the Acoustical Society America , 67, 1781-1784. Za lewski , J., Majewski , W. & Hollien , H . (1975) Cross-correlation of long-te rm speech spectra as a speaker identification technique , Acustica, 34, 20-24 .
Appendix
Catalan text El barri de xalets de Sitges era un Hoc on m'agradava d'anar a passejar a omenc;aments de temporada. I Ia platja era el lloc on feiem Ia primera cabussada de Ia temporada amb les noies del pis. No ens agradava tant com les platges de \f allorca pen) de tots els llocs de Ia costa baixa proxima a Barcelona era el mes passador. Els mallorquins sempre trobem a faltar Ia nostra terra que jutgem millor. \1 es endavant elles se n'anaven a l'illa a passar l'estiu i jo tornava a banyar-m'hi se mpre que podia. Ara ja feia dotze anys que no hi havia vingut. { ~I
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Spanish text El joyero Federico Vanero ha sido condenado porIa Audiencia de Santander a ocho meses de arresto mayor y cincuenta mil pesetas de multa por un delito de compra de objetos robados. La vistra oral se celebr6 el miercoles pasado y, durante ella, uno de los fiscales, Carlos Valcarcel, pidi6 para el joyero tres afios de prisi6n menor y una multa de cincuenta mil pesetas. Gracias a las revelacinoes de Vanero de hace dos afios y media se lleg6 a descubrir Ia existencia de una sospechosa mafia policial en Espana, parte de Ia cual se vio envuelta en el llamado " caso El Nani". {el xoj.ero federiko banero a sido kondenado por Ia audien9ia de santander a otfo meses de aresto maior i 9inkuenta mil pesetas de multa por un delito de kompra de obxetos robados Ia bista oral se 9elebro el mierkoles pasado i durante eA.a uno de los fiskales karlos alk ar9el pidio para al xoj.ero tres apos de prision menor i una multa de 9inkuenta mil pesetas . == ra9ias a las rebela9iones de banero de aee dos apos i medio se A.ego a deskubrir Ia egsisten9ia de una sospetfosa mafia poli9ial en espapa parte de Ia kual se bj.o em buelta en el A.amado kaso el nani]