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Comparison of Dysphonia Severity Index Between Younger and Older Carnatic Classical Singers and Nonsingers
Comparison of Dysphonia Severity Index Between Younger and Older Carnatic Classical Singers and Nonsingers Santosh Maruthy and Preethi Ravibabu, Mysore, Karnataka, India Summary: Objectives. The main objective of this study was to compare dysphonia severity index (DSI) and its parameters between Carnatic classical singers and nonsingers. The second objective was to investigate the effect of age on DSI and its parameters in both singers and nonsingers. Study Design. This study included 30 female Carnatic classical singers who were subdivided into two groups based on their age: 15 younger singers and 15 older singers. These 30 singers were compared with 30 age and gender matched nonsingers. Methods. From each participant, measures of highest phonational frequency, lowest intensity, jitter, and maximum phonation time were obtained. Using these, DSI values were calculated. Results. Singers had significantly greater highest phonational frequency, longer maximum phonation time, and higher DSI values. When compared with the younger participants, older participants had significantly reduced highest phonational frequency, maximum phonation time, and DSI values. Conclusions. The results of this study suggest that DSI values vary between Carnatic classical singers and nonsingers, and hence separate normative data may need to be established for this group of singers for clinical comparison purposes. Key Words: Dysphonia severity index–Singers–Maximum phonation time–Jitter–Aging–Acoustic analysis.
INTRODUCTION Dysphonia severity index (DSI)1 is an objective, multidimensional measure of vocal performance. DSI is calculated by taking into account four separate voice parameters: highest phonational frequency (F0-high in Hz), lowest intensity (Ilow in dB), maximum phonation time (MPT in seconds), and jitter (%). These four parameters are used to calculate DSI from the following formula: DSI ¼ 0:13 3 MPT ðsecondsÞ þ 0:0053 3 F0 high ðHzÞ 0:26 3 I low ðdBÞ 1:18 3 jitter ð%Þ þ 12:4 DSI has been used both as an initial diagnostic tool and as an outcome measure of treatment efficacy. The values of DSI may range from +5 (indicating normal voice) to 5 (indicating severe dysphonia).1 It has been reported that DSI correlates well with the perceived voice quality, and is very sensitive to slight changes in the voice quality and vocal function.1,2 However, there was no significant correlation between DSI values and voice handicapped index.3 Further, DSI values change based on specific management for voice problems.4 While comparing the DSI values of the disordered population, it has been suggested that the DSI is influenced by age and gender, and hence extensive normative data need to be obtained for the specific population.5 Thus, for the specific type of Accepted for publication May 1, 2014. From the Department of Speech Language Sciences, All India Institute of Speech and Hearing, Mysore, Karnataka, India. Address correspondence and reprint requests to Santosh Maruthy, Department of Speech Language Sciences, All India Institute of Speech and Hearing, Manasagangothri, Mysore, Karnataka, India 570006. E-mail: [email protected] Journal of Voice, Vol. 29, No. 1, pp. 65-70 0892-1997/$36.00 Ó 2015 The Voice Foundation http://dx.doi.org/10.1016/j.jvoice.2014.05.001
professional voice users such as singers separate normative data for DSI need to be established.6 This is necessary because many studies have reported superior performance of singers compared with nonsingers with respect to respiratory capacities,7,8 fundamental frequency range,9–11 dynamic range,10,12 and breath control.13 However, only one study has compared DSI values between singers and nonsingers.6 The results suggested that trained Western classical singers had greater mean F0-high, lower intensity, and lower jitter values compared with untrained participants. The overall DSI score was also found to be greater in trained singers. The present study compared DSI values between Carnatic classical singers and nonsingers. Carnatic classical singing is the traditional South Indian classical singing style. In this singing style, training typically starts at a very young age (5– 6 years) under the mentorship of an accomplished music teacher called ‘‘guru’’. Usually the training is on a one-to-one basis. The training is structured with the initial training focused on singing the right notes called ‘‘swaras’’. After this, training progresses to a stage where singers learn to sing different compositions called ‘‘ragas’’. These ‘‘ragas’’ are the basis of classical music. The rhythmic structure of each composition is called as ‘‘tala’’. Typically, the compositions are within 2–2.5 octaves. Unlike Western classical music where singers sing at one particular pitch (eg, bass, baritone, tenor, or soprano), Carnatic classical singers adjust their base pitch called ‘‘aadhara shruthi’’ depending on the ‘‘raga’’. Based on the ‘‘aadhara shruthi’’ the other notes in the composition are adjusted. Like Western classical singers, Carnatic singers undergo regular training and practice to achieve proficiency in singing.14 Like any other professional voice users, Carnatic singers may also experience voice problems. However, because of their increased vocal capabilities, their DSI values may fall within the normal ranges of nonsingers.6,14
66 Further, the values of DSI in Carnatic classical singers may vary compared with Western classical singers because of differences in ethnic and geographic characteristics between two groups of population. One recent study in Asian Indian population15 provided corroborative evidence for this proposition. These authors investigated the effect of geographical and ethnic variation on DSI and its parameters. When they compared their results with the previously published data on DSI and its parameters in Western population, they found significant differences in MPT, F0-high, and DSI values for Asian Indian population. The MPT values were found to be less in Indian population. Further, they also found a significant effect of gender on DSI and its parameters. Hence, there is a need to compare DSI values for trained Carnatic singers with nonsingers. The second goal of the study was to investigate the effect of aging on DSI and its parameters in both singers and nonsingers. Several studies have documented the effect of aging in nonsingers for different individual acoustic measures of voice. From adulthood to old age, speaking fundamental frequency (SFF) differently changes in both males and females. As the age progresses, in males SFF rises,16–18 whereas in females, it lowers.18–20 With respect to conversational intensity levels, in males, higher intensity levels were found in older individuals compared with younger individuals, whereas in females, there were no age-related changes in intensity levels.21,22 Multiple studies have also reported both jitter18,23–25 and shimmer increase with age.18,20 However, there is no consistent finding with respect to the effect of aging on MPT values. Few studies have reported reduced MPT values in older participants (both males and females),26–28 whereas one recent study reported longer MPT values in older females compared with younger females,20 and another study reported no significant decrease in MPT values in older participants (both males and females) compared with young adults.29 One possible reason for this could be that MPT is influenced by many factors like testing conditions and number of trials, and hence it lacks reliability and validity.30,31 In nonsingers, only two studies have investigated the effect of aging on DSI and its related parameters. Hakkesteegt et al,5 investigated the effect of age and gender on DSI and its parameters. They found significant effect of age on DSI, F0-high, and I-low measures. However, gender had significant effect only on the MPT and F0-high measures. Recently, Goy et al,20 reported that older females had higher DSI values than younger females. However, there was no difference in the DSI values between young and older males. Few studies have documented the effect of aging on the singers’ acoustic measures of voice. The evidence from these studies suggests that singers even in their old age typically had stable SFF,32,33 significantly less jitter,34 greater intensity,34 and wider phonational ranges35 compared with nonsingers. However, there was no significant difference between older singers and nonsingers on shimmer and F0.34 Overall, most of the previous researches are focused on individual acoustic parameters, and haven’t studied the effect of aging in singers on DSI and its component parameters. Clearly, further data are needed to understand whether training in classical singing re-
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duces the effect of aging on DSI in singers compared with nonsingers. Hence, the aim of the present study was to compare DSI scores in trained Carnatic classical singers and nonsingers. The second purpose was to investigate the effect of aging on DSI and its parameters in singers and nonsingers. METHOD Participants Thirty female trained Carnatic classical singers participated in the present study. These thirty singers were subgrouped into two based on their age: 15 younger singers and 15 older singers. Younger singers were those individuals who were aged below fifty years and older singers were those who were aged above fifty years. The mean age of younger singers was 28.33 years (standard deviation [SD], 10.31; age range, 19–48 years). Their mean number of years of training was 19 years (SD, 6.88). Their mean duration of practice per day was 2.2 hours (SD, 1.89). Their mean body mass index (BMI) was 22.5 (SD, 2.47). The mean age of the older singers was 59.33 years (SD, 5.44; age range, 51–72 years). Their mean number of years of training was 35.26 years (SD, 7.21). Their mean duration of practice per day was 2.6 hours (SD, 1.24). Their mean BMI was 24.5 (SD, 3.24). At the time of recording all the singers were actively involved in vocal training. For comparison purposes, thirty age and gender matched nonsingers served as a control group. These nonsingers did not have any formal training in singing, including choral singing. Again, nonsingers were subdivided into 15 younger nonsingers and 15 older nonsingers. The mean age of younger nonsingers was 28.33 years (SD, 10.31; age range, 19–48 years). The mean age of older nonsingers was 58.93 years (SD, 4.77; age range, 51–68 years). The mean BMI for the younger nonsinger group was 21.1 (SD, 1.41). The mean BMI for the older nonsinger group was 23.6 (SD, 1.55). All the participants were recruited from Mysore, Karnataka, India. By taking detailed demographic history, participants were assessed for any speech, hearing, or neurological problems. Only those participants without any speech, hearing, or neurological problems were selected. Further, these participants did not have any medical conditions which could influence respiratory and phonatory functions. Hearing evaluation was done using calibrated clinical audiometer (Madsen Orbitor 922; GN Otometrics, Denmark) in a sound proofed room. All the participants had their air and bone conduction hearing thresholds less than 15 dBHL at octave frequencies 250 Hz to 8 kHz. Further, to check for any voice problem, a certified speech-language pathologist perceptually rated their voice quality using the GRBAS (grade, roughness, breathiness, asthenic, and strainness) scale.36 Both singers and nonsingers had normal voice quality. Instrumentation and recording procedure The recording was carried out in a sound-treated room using Ling Waves instrument (WEVOSYS, Germany). Ling Waves is a high quality software-hardware unit which analyses the human voice. Ling Waves comes with a sound level meter (SLM) with a microphone attached to it. The SLM was placed on a
Santosh Maruthy and Preethi Ravibabu
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Comparing DSI of Carnatic Classical Singers and Nonsingers
tripod stand, and through this stand the SLM was adjusted to the patient’s mouth level. The Ling Waves software is a combined analysis tool for the measurement of the quantitative (singing/ voice range profile) and qualitative voice parameters. It consists of different modules. It has a separate module for the calculation of the DSI parameters. The noise level inside the room was less than 30 dB SPL (sound pressure level). As recommended by Ling Waves manual the participants were made to stand and do the following mentioned tasks. The microphone was adjusted according to the height of the participant. To avoid any distortions during the recording a distance of 30 cm was maintained between the microphone and the participant’s mouth. The participants were explained about the task and the second author demonstrated each task to the participants. The participants were given three trials for each task and the average was taken for each parameter. The following tasks were recorded from each participant. Tasks 1. Highest phonational frequency (F0-high): The participants were asked to phonate vowel /a/ from comfortable pitch to the highest pitch possible without any pitch breaks. They were also instructed not to use the false voice during the phonation. 2. Lowest intensity level (I-low): The participants were asked to sustain the vowel /a/ at a comfortable pitch from the softest loudness to the maximum loudness possible. In another way, the participant can start phonating at comfortable loudness and then slowly decrease the loudness level to the softest loudness they can go. 3. Jitter (%): The participants were instructed to produce sustained phonation of the vowel /a/ at a comfortable pitch and loudness for 2–3 seconds. The selected portion (2–3 seconds) of phonation was used for the jitter calculation. 4. Maximum phonation time (MPT): The participants were instructed to take a deep breath/inhale deeply and sustain vowel /a/ as long as possible at a comfortable pitch and loudness. The participants were instructed to use the maximum amount of air from their lung capacity.
Using the previously mentioned four parameters the DSI was calculated from the following formula: DSI ¼ 0:13 3 MPT ðsecondsÞ þ 0:0053 3 F0 high ðHzÞ 0:26 3 I low ðdBÞ 1:18 3 jitter ð%Þ þ 12:4 Statistical analysis Commercially available SPSS software (IBM, New York, NY) was used for statistical analysis. For the highest phonation frequency, the lowest intensity level, and MPT measures, analysis of variance (ANOVA) was completed with two levels of group (singers vs nonsingers) and two levels of age (younger vs older). An alpha level of 0.05 was selected. Post hoc analysis was done using independent sampled t test. For the DSI measure, as the standard deviation values were higher than the mean values for two groups (old singers and nonsingers), nonparametric Mann-Whitney U test was done. RESULTS Highest phonational frequency (F0-high) The results of two-way ANOVA for F0-high suggested significant main effects of group [F (1, 56) ¼ 119.761, P < 0.01] and age [F (1, 56) ¼ 93.317, P < 0.01]. Further, there was a significant interaction effect of groups versus age [F (1, 56) ¼ 21.840, P < 0.001]. Post hoc analysis using independent t test showed a significant difference between younger versus older participants for both singers [t (28) ¼ 8.439, P < 0.001] and nonsingers [t (28) ¼ 4.722, P < 0.001]. Further, a significant difference between singers versus nonsingers was found for both younger [t (28) ¼ 9.525, P < 0.001] and older [t (28) ¼ 5.474, P < 0.001] participants. Younger singers had significantly greater F0-high values compared with older singers. Further, both younger and older singers had significantly greater F0-high values compared with younger and older nonsingers (Table 1). Lowest intensity level (I-low in dB) The results of two-way ANOVA for the lowest intensity level suggested no significant main effect of group [F (1, 56) ¼ 0.031, P ¼ 0.861]. However, there was a significant main effect of age [F (1, 56) ¼ 10.446, P ¼ 0.002]. Younger
TABLE 1. Comparison of Means and SDs for the DSI and its Component Measures Between Younger and Older Carnatic Classical Singers and Nonsingers
Variable MPT (s) F0-high (Hz) I-low (dB) Jitter (%) DSI
Singers (Younger)
Singers (Older)
Nonsingers (Younger)
Nonsingers (Older)
(n ¼ 15)
(n ¼ 15)
(n ¼ 15)
(n ¼ 15)
15.58 (2.52) 982.15 (140.54) 54.92 (3.33) 0.155 (0.054) 5.16 (1.24)
11.01 (3.16) 595.79 (108.13) 61.90 (8.86) 0.130 (0.041) 0.744 (1.96)
12.95 (2.29) 561.19 (97.73) 57.62 (4.13) 0.175 (0.032) 1.82 (0.93)
10.058 (1.55) 426.77 (51.04) 59.70 (3.36) 0.146 (0.042) 0.27 (0.77)
Notes: SDs are provided in the parentheses.
68 participants (both singers and nonsingers) produced significantly lower intensity phonations compared with the older participants (Table 1). Nevertheless, there was no significant interaction effect between the group versus age [F (1, 56) ¼ 3.039, P ¼ 0.087]. Jitter (%) The results of two-way ANOVA for jitter (%) showed no significant main effect of group [F (1, 56) ¼ 2.519, P ¼ 0.118]. However, there was a significant main effect of age [F (1, 56) ¼ 5.853, P ¼ 0.019]. Younger participants (both singers and nonsingers) had significantly higher mean jitter values compared with the older participants (Table 1). Nevertheless, there was no significant interaction between groups versus age. Maximum phonation time (MPT in seconds) The results suggested a significant main effect of group (F (1, 56) ¼ 8.016, P ¼ 0.006) and age (F (1, 56) ¼ 34.731, P < 0.001). However, there was no significant interaction effect between groups versus age (F (1, 56) ¼ 1.733, P ¼ 0.193). Overall, singers had significantly longer MPT values compared with nonsingers (Table 1). Further, younger participants (both singers and nonsingers) had significantly longer MPT values compared with the older participants (both singers and nonsingers). Dysphonia severity index The results suggested statistically significant difference between singers versus nonsingers [U (56) ¼ 4.00, Z ¼ 3.208, P ¼ 0.001], and between younger versus older participants [U (56) ¼ 97.000, Z ¼ 5.219, P ¼ 0.000]. Post hoc analysis indicated significant difference between younger versus older participants for both singers [U (28) ¼ 2.000, Z ¼ 4.584, P ¼ 0.000] and nonsingers [U (28) ¼ 21.000, Z ¼ 3.796, P ¼ 0.000]. However, between singers versus nonsingers there was statistically significant difference only for younger participants {younger [U (28) ¼ 4.000, Z ¼ 4.501, P ¼ 0.00]; older [U (28) ¼ 78.000, Z ¼ 1.431, P ¼ 0.161]}. DISCUSSION The main purpose of the present study was to compare DSI values between trained Carnatic classical singers and nonsingers. The second purpose was to investigate the effect of age on DSI values in singers and nonsingers. Highest phonational frequency (F0-high) Carnatic classical singers (both younger and older) had significantly greater F0-high values compared with nonsingers (Table 1). Similar results are reported with Western Classical singers where greater F0-high values were found in both male and female singers compared with nonsingers.6 Using phonetogram, Awan 10 also reported greater F0-high values in trained singers compared with untrained singers. However, Brown et al,35 found statistically no significant difference between singers and nonsingers. Increased F0-high values in Carnatic classical singers compared with nonsingers may be because of training in singing. Like Western classical singing, Carnatic classical singers go through rigorous training for pitch matching,
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pitch gliding, and singing at different pitch (musical) scales. As a result of this training, singers may be able to produce greater frequency ranges and maximum frequencies than nonsingers. The results showed that F0-high values were significantly lower in older participants (both singers and nonsingers) compared with the younger participants. Reduced F0-high values in older nonsingers are consistent with previous studies.5,37 However, Goy et al,20 found no difference in F0high values between young and old females. The lowering of F0-high values with advancing age may be attributed to increase in the vocal fold edema, decrease in the elasticity of vocal folds, weakening of the intrinsic muscles, increase in the vocal fold mass, and ossification and calcification of the laryngeal cartilages.38,39 The significant decrease in the F0-high values in older singers compared with the younger singers suggests that the lowering of the highest phonational frequency is a biologically determined phenomenon and can occur even in the trained singers.35 Hence, Carnatic classical singers may need to adjust (lower) their ‘‘aadhaara shruthi’’ (base pitch) with aging. However, older singers’ F0-high values were still significantly greater than older nonsingers. This suggests that with aging structural changes in the vocal folds of singers may be characteristically different compared with nonsingers. Lowest intensity level (I-low) Statistically no significant difference was found between singers and nonsingers for I-Low values during phonation. The present results suggest that although Carnatic singers had slightly lower I-low values, they were similar to nonsingers. The present results are in contrast to previous findings in the literature,6,10,40 where they found significantly lower I-low values in Western singers compared with nonsingers. The reason for significantly lower I-low values in Western singers has been attributed to the effect of vocal training. With vocal training, singers are supposed to develop better abdominal support and greater control over their loudness ranges. Hence, they may be able to produce vocal intensities at lower levels. One another reason suggested is that training in Western classical singing includes specific respiratory and warm-up exercises for strengthening of abdominal muscles and diaphragm.6,41 Such systematic exercises for strengthening respiratory support are not present during training in Carnatic classical singing. Carnatic singing only emphasizes on singing at the right tonic pitch and tonal quality. Further, Carnatic singing is loud singing.14 Hence, the vocal folds may be more tuned to singing/phonating at louder voices compared with softer voices. Further studies need to be done to corroborate present findings. Younger individuals produced significantly lower intensity phonations compared with older individuals. Present results are in accordance with previous literature,5,37 and suggest that with aging there is reduced control over the breath support and phonatory abilities. This could be the reason for increased I-low values in older participants.5 Jitter (%) Overall, there was no significant difference between the singers and nonsingers for jitter (%) values (Table 1). Present results are
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Comparing DSI of Carnatic Classical Singers and Nonsingers
in contrast to study by Awan and Ensslen,6 who found that nonsingers had significantly higher jitter values compared with trained singers. Interestingly, in the present study, younger participants had significantly higher jitter values compared with the older participants. However, in both the groups of participants, jitter values were within the accepted normal limits (1%). It is reported that the values of jitter need to be viewed cautiously as multiple factors like the sound pressure level of phonation,42,43 mean fundamental frequency of phonation,44 health and fitness of participants can influence them. Hence, it is difficult to arrive at the firm conclusion about the effect of aging on jitter values. With increasing age, some previous studies have found increased jitter values,18,23–25,45 whereas few others have reported no changes in jitter values.5,20 Maximum phonation time (MPT) Singers had significantly longer MPT values compared with nonsingers (Table 1). MPT reflects coordination between breathing and phonation.46 So it was hypothesized that because of regular training, singers may have better coordination between two subsystems and hence longer MPT values. Early attempts to compare MPT values between singers and nonsingers have yielded inconsistent results. Caroll et al,47 found reduced MPT values in classically trained singers when compared with few selected previously published normative values. However, Awan and Ensslen6 reported no significant differences on MPT measures between trained and untrained vocalists. All the singers in the present study had at least 10 years of vocal training, and hence they may have better control over their respiratory support and glottal valving. The mean MPT values of younger individuals were significantly longer compared with older individuals, which is consistent with previous studies.5,26,27 Reduced MPT values in older individuals could be because of both structural and functional changes in respiratory and laryngeal systems with aging. Structural changes reported include reduced elasticity and muscle strength, increased stiffness in the thorax, loss of lung tissue elasticity, weakening of respiratory muscles, and degenerative changes in the laryngeal muscles.27,48,49 Functional changes reported include decreased elastic recoil forces of lung tissues, reduced vital capacity, increased residual volume, and reduced expiratory/inspiratory volume.50 When compared with Western norms, the mean MPT values in our participants (both singers and nonsingers) were significantly lower. According to Hirano,36 MPT values in normal males should be 34.6 seconds, and in females, 25.7 seconds. However, in Indian context, Jayakumar and Savithri15 found differences in the MPT values between the Indian and European population. They found MPT values to be 17.6 seconds for males and 13.8 seconds for females. This difference between Western data and Asian Indian data may be because of variation in the geographic and physical condition of individuals. The average Asian Indians are shorter and have less body mass compared with Caucasians.51 Further, they also have shorter and narrower chests compared with Caucasians.52 Because of this, their vital capacities and lung volumes are reduced compared with Caucasians.53–55 It is known that vital
69
capacity and lung volumes significantly correlate with the MPT values,56 In India, the MPT values again vary between the singers and nonsingers group. Dysphonia severity index (DSI) The mean DSI values were significantly higher in younger singers compared with nonsingers (Table 1), which is consistent with Awan and Ensslen 6 findings. They also reported that the DSI values to be significantly higher in the trained vocalist group (6.35) compared with the untrained group (4.69). Timmerman, et al,57,58 found that the DSI values increased in the vocally trained group compared with the untrained group. The increase in DSI values in singers may be mainly because of the increased F0-high and longer MPT values which contributed to the overall increase in the DSI value. As the factorial influences of the components of the DSI were not done further studies need to be done to corroborate present claim. Further, when compared with Western classical singers, our singers had significantly lower DSI values. This difference may be mainly because of reduced MPT values in Carnatic classical singers compared with Western classical singers. The effect of age on DSI values were noted in both singers and nonsingers. Both younger singers and nonsingers had significantly greater DSI values compared with older singers and nonsingers respectively. This reduction in DSI values in older participants could be mainly because of lowering of F0high,5 and reduction in MPT values. As there is no significant difference between DSI values in old singers and nonsingers, it may be necessary to establish separate normative data for DSI values only for young singers. Collectively, in this study we found that Carnatic classical singing had a significant effect on DSI and two of its parameters (MPT and F0-high). Singers had significantly longer MPT, greater F0-high, and because of this higher DSI values. Age also had a significant effect on both singers and nonsingers. When compared with the younger participants, older participants had reduced MPT, F0-high, and DSI values. Results suggest that separate normative data may need to be established for singers and nonsingers for DSI and its parameters by taking age into consideration. As the sample size of singers and nonsingers was small further studies need to be done with a larger sample to corroborate present findings. Additionally, studies can also be taken up with male Carnatic classical singers to extend the current findings. Future studies are also needed to explore whether the significant difference noticed between singers and nonsingers could be mainly because of training or due to innate special abilities of singers. Acknowledgments The authors would like to thank Dr. S.R. Savithri, Director, All India institute of Speech and Hearing, Mysore, India, for allowing us to carry out this study. We also thank all the participants. REFERENCES 1. Wuyts FL, De Bodt MS, Molenberghs G, et al. The dysphonia severity index: an objective measure of vocal quality based on a multiparameter approach. J Speech Lang Hear Res. 2000;43:796–809.
70 2. Hakkesteegt MM, Brocaar MP, Wieringa MH, Feenstra L. The relationship between perceptual evaluation and objective multiparametric evaluation of dysphonia severity. J Voice. 2008;22:138–145. 3. Hakkesteegt MM, Brocaar MP, Wieringa MH. The applicability of the dysphonia severity index and the voice handicap index in evaluating effects of voice therapy and phonosurgery. J Voice. 2010;24:199–205. 4. Van Lierde KM, De Bodt M, Dhaeseleer E, Wuyts F, Claeys S. The treatment of muscle tension dysphonia: a comparison of two treatment techniques by means of an objective multiparameter approach. J Voice. 2010;24:294–301. 5. Hakkesteegt MM, Brocaar MP, Wieringa MH, Feenstra L. Influence of age and gender on the dysphnia severity index: A study of normative values. Folia Phoniatr Logop. 2006;58:264–272. 6. Awan SN, Ensslen AJ. A comparison of trained and untrained vocalists on the Dysphonia severity index. J Voice. 2009;24:661–666. 7. Gould W. The effect of voice training on lung volumes in singers and the possible relationship to the damping factor of pressman. J Res Sing. 1977;1:3–15. 8. Watson PJ, Hixon TJ. Respiratory kinematics in classical (opera) singers. J Speech Hear Res. 1985;28:104–122. 9. Troup G. The physics of the singing voice. J Res Sing. 1982;6:1–26. 10. Awan SN. Phonetographic profiles and frequency-SPL characteristics of untrained versus trained vocal groups. J Voice. 1991;5:41–50. 11. Titze I. Principles of the Singing Voice. Englewood Cliffs, NJ: Prentice Hall; 1994. 12. Murbe D, Sundberg J, Iwarsson J, Pabst F. Phonetogram measurements of singers. Before and after solo singer education. TMH-QPSR. 1996;37:49–56. 13. Sulter AM, Schutte HK, Miller DG. Differences in phonetogram features between male and female subjects with and without vocal training. J Voice. 1995;9:363–377. 14. Arunachalam R, Boominathan P, Mahalingam S. Clinical voice analysis of carnatic singers. J Voice. 2014;28:128.e1–128.e9. 15. Jayakumar T, Savithri SR. Effect of geographical and ethnic variation on dysphonia severity index: a study of indian population. J Voice. 2012;26: e11–e16. 16. Segre R. Senescence of the voice. Eye Ear Nose Throat Mon. 1971;50: 223–227. 17. Kahane JC. Connective tissue changes in the larynx and their effects on voice. J Voice. 1987;1:27–30. 18. Dehqan A, Scherer RC, Dashti G, Ansari-Moghaddam A, Fanaie S. The effects of aging on acoustic parameters of voice. Folia Phoniatr Logop. 2012; 64:265–270. 19. de Pinto O, Hollien H. Speaking fundamental frequency characteristics of Australian women: then and now. J Phonet. 1982;10:367–375. 20. Goy H, Fernandes DN, Kathleen Pichora-Fuller M, van Lieshout P. Normative voice data for younger and older adults. J Voice. 2013;27:545–555. 21. Ryan W. Acoustic aspects of the aging voice. J Gerontol. 1972;27:265–268. 22. Morris RJ, Brown WS Jr. Age-related differences in speech intensity among adult females. Folia Phoniatr Logop. 1994;46:64–69. 23. Mysak ED. Pitch and duration characteristics of older males. J Speech Hear Res. 1959;2:46–54. 24. Wilcox KA, Horri Y. Age and changes in vocal jitter. J Gerontol. 1980;35: 194–198. 25. Linville SE, Fisher HB. Acoustic characteristics of women’s voices with advanced age. J Gerontol. 1985;40:324–330. 26. Ptacek PH, Sander EK, Mahoney W, Jackson C. Phonatory and related changes with advanced age. J Speech Hear Res. 1966;9:353–360. 27. Kreul EJ. Neuromuscular control examination (NMC) for Parkinsonism: vowel prolongations and diadochokinetic and reading rates. J Speech Hear Res. 1972;15:72–83. 28. Mueller PB. Voice characteristics of octogenarian and nonagenerian persons. Ear Nose Throat J. 1982;61:33–37. 29. Maslen J, Leng X, Rees C, Blalock D, Butler SG. Maximum Phonation Time in Healthy Older Adults. J Voice. 2011;25:709–713. 30. Neiman GS, Edeson B. Procedural aspects of eliciting maximum phonation time. Folia Phoniatr. 1981;33:285–293.
Journal of Voice, Vol. 29, No. 1, 2015 31. Lewis K, Casteel R, McMahon J. Duration of sustained /a/ related to the number of trials. Folia Phoniatr. 1982;34:41–48. 32. Brown WS, Morris RJ, Michel JF. Vocal jitter and fundamental frequency characteristics in aged, female professional singers. J Voice. 1990;4: 135–141. 33. Brown WS, Morris RJ, Hollien H, Howell E. Speaking fundamental frequency characteristics as a function of age and professional singing. J Voice. 1991;5:310–315. 34. Prakup B. Acoustic measures of the voices of older singers and nonsingers. J Voice. 2012;26:341–350. 35. Brown WS, Morris RJ, Hicks D, Howell E. Phonational profiles of female professional singers and nonsingers. J Voice. 1993;7:219–226. 36. Hirano M. Clinical examination of voice. New York, NY: Springer; 1981. 37. Teles-Magalhaes LC, Pegoraro-Krook MI, Pegoraro R. Study of the elderly females’ voice by phonetography. J Voice. 2000;14:310–321. 38. Paulsen F, Kimpel M, Lockemann U, Tillmann B. Effects of aging on the insertion zones of the human vocal fold. J Anat. 2000;196:41–54. 39. Linville SE. Vocal aging. San Diego, CA: Singular Publishers; 2001. 40. LeBorgne WD, Weinrich BD. Phonetogram changes for trained singers over a nine-month period of vocal training. J Voice. 2002;16:37–43. 41. Mendes A, Rothman H, Sapienza C, Brown WS. Effects of vocal training on the acoustic parameters of the singing voice. J Voice. 2003;17:529–543. 42. Lee L, Stemple J, Kizer M. Consistency of acoustic and aerodynamic measures of voice production over 28 days under various testing conditions. J Voice. 1999;13:477–483. 43. Orlikoff R, Kahane J. Influence of mean sound pressure level on jitter and shimmer measures. J Voice. 1991;5:113–119. 44. Orlikoff R, Baken R. Considearation of the relationship between the fundamental frequency of phonation and vocal jitter. Folia Phoniatr. 1990;42: 31–40. 45. Orlikoff R. The relationsip of age and cardiovascular health to certain acoustic characteristics of male voices. J Speech Hear Res. 1990;33: 450–457. 46. Arnold GE. Vocal rehabilitation of paralytic dysphonia: II. Acoustic analysis of vocal function. Arch Otolaryngol. 1955;62:593–601. 47. Carroll LM, Sataloff RT, Heuer RJ, Spiegel JR, Radionoff SL, Cohn JR. Respiatory and glottal efficiecy measures in normal classically trained singers. J Voice. 1996;10:139–145. 48. Mahler D. Pulmonary aspects of aging. In: Gambert SR, ed. Contemporary Geriatric Medicine, Vol 1. New York, NY: Plenum Medical Book Company; 1983:45–85. 49. Sataloff RT, Rosen DC, Hawkshaw M, Spiegel JR. The aging adult voice. J Voice. 1997;11:156–160. 50. Satallof RT, Linville SE. The effects of age on the voice. In: Sataloff RT, ed. Professional voice: the science and art of clinical care, Cap 27. New York, NY: Raven Press; 1991:497–511. 51. Marshall WA. Geographical and ethnic variations in human growth. Br Med Bull. 1981;37:273–279. 52. Donnelly PM, Yang TS, Peat JK, Woolcock AJ. What factors explain racial differences in lung volumes? Eur Respir J. 1991;4:829–838. 53. Rajeev P. A normative data on aerodynamic parameters in normal adults [unpublished master dissertation]. Mysore, India: University of Mysore; 1995. 54. Kamat SR, Tyagi NK, Rashid SSA. Lung function in Indian adult subjects. Lung India. 1982;1:11–21. 55. Mathew L, Sengupta J, Lakhura SC, Raman CV. Age related changes in lung functions in Indian servicemen. Indian J Med Res. 1984;79:529–537. 56. Yanagihara N, Koike Y. The regulation of sustained phonation. Folia Phoniatr. 1967;19:1–18. 57. Timmermans B, De Bodt M, Wuyts F, Heyning P. Voice quality change in future professional voice users after 9 months of voice training. Eur Arch Otorhinolaryngol. 2004;261:1–5. 58. Timmermans B, De Bodt MS, Wuyts FL, Van de Heyning PH. Analysis and evaluation of a voice-training program in future professional voice users. J Voice. 2005;19:202–210.
INTRODUCTION Dysphonia severity index (DSI)1 is an objective, multidimensional measure of vocal performance. DSI is calculated by taking into account four separate voice parameters: highest phonational frequency (F0-high in Hz), lowest intensity (Ilow in dB), maximum phonation time (MPT in seconds), and jitter (%). These four parameters are used to calculate DSI from the following formula: DSI ¼ 0:13 3 MPT ðsecondsÞ þ 0:0053 3 F0 high ðHzÞ 0:26 3 I low ðdBÞ 1:18 3 jitter ð%Þ þ 12:4 DSI has been used both as an initial diagnostic tool and as an outcome measure of treatment efficacy. The values of DSI may range from +5 (indicating normal voice) to 5 (indicating severe dysphonia).1 It has been reported that DSI correlates well with the perceived voice quality, and is very sensitive to slight changes in the voice quality and vocal function.1,2 However, there was no significant correlation between DSI values and voice handicapped index.3 Further, DSI values change based on specific management for voice problems.4 While comparing the DSI values of the disordered population, it has been suggested that the DSI is influenced by age and gender, and hence extensive normative data need to be obtained for the specific population.5 Thus, for the specific type of Accepted for publication May 1, 2014. From the Department of Speech Language Sciences, All India Institute of Speech and Hearing, Mysore, Karnataka, India. Address correspondence and reprint requests to Santosh Maruthy, Department of Speech Language Sciences, All India Institute of Speech and Hearing, Manasagangothri, Mysore, Karnataka, India 570006. E-mail: [email protected] Journal of Voice, Vol. 29, No. 1, pp. 65-70 0892-1997/$36.00 Ó 2015 The Voice Foundation http://dx.doi.org/10.1016/j.jvoice.2014.05.001
professional voice users such as singers separate normative data for DSI need to be established.6 This is necessary because many studies have reported superior performance of singers compared with nonsingers with respect to respiratory capacities,7,8 fundamental frequency range,9–11 dynamic range,10,12 and breath control.13 However, only one study has compared DSI values between singers and nonsingers.6 The results suggested that trained Western classical singers had greater mean F0-high, lower intensity, and lower jitter values compared with untrained participants. The overall DSI score was also found to be greater in trained singers. The present study compared DSI values between Carnatic classical singers and nonsingers. Carnatic classical singing is the traditional South Indian classical singing style. In this singing style, training typically starts at a very young age (5– 6 years) under the mentorship of an accomplished music teacher called ‘‘guru’’. Usually the training is on a one-to-one basis. The training is structured with the initial training focused on singing the right notes called ‘‘swaras’’. After this, training progresses to a stage where singers learn to sing different compositions called ‘‘ragas’’. These ‘‘ragas’’ are the basis of classical music. The rhythmic structure of each composition is called as ‘‘tala’’. Typically, the compositions are within 2–2.5 octaves. Unlike Western classical music where singers sing at one particular pitch (eg, bass, baritone, tenor, or soprano), Carnatic classical singers adjust their base pitch called ‘‘aadhara shruthi’’ depending on the ‘‘raga’’. Based on the ‘‘aadhara shruthi’’ the other notes in the composition are adjusted. Like Western classical singers, Carnatic singers undergo regular training and practice to achieve proficiency in singing.14 Like any other professional voice users, Carnatic singers may also experience voice problems. However, because of their increased vocal capabilities, their DSI values may fall within the normal ranges of nonsingers.6,14
66 Further, the values of DSI in Carnatic classical singers may vary compared with Western classical singers because of differences in ethnic and geographic characteristics between two groups of population. One recent study in Asian Indian population15 provided corroborative evidence for this proposition. These authors investigated the effect of geographical and ethnic variation on DSI and its parameters. When they compared their results with the previously published data on DSI and its parameters in Western population, they found significant differences in MPT, F0-high, and DSI values for Asian Indian population. The MPT values were found to be less in Indian population. Further, they also found a significant effect of gender on DSI and its parameters. Hence, there is a need to compare DSI values for trained Carnatic singers with nonsingers. The second goal of the study was to investigate the effect of aging on DSI and its parameters in both singers and nonsingers. Several studies have documented the effect of aging in nonsingers for different individual acoustic measures of voice. From adulthood to old age, speaking fundamental frequency (SFF) differently changes in both males and females. As the age progresses, in males SFF rises,16–18 whereas in females, it lowers.18–20 With respect to conversational intensity levels, in males, higher intensity levels were found in older individuals compared with younger individuals, whereas in females, there were no age-related changes in intensity levels.21,22 Multiple studies have also reported both jitter18,23–25 and shimmer increase with age.18,20 However, there is no consistent finding with respect to the effect of aging on MPT values. Few studies have reported reduced MPT values in older participants (both males and females),26–28 whereas one recent study reported longer MPT values in older females compared with younger females,20 and another study reported no significant decrease in MPT values in older participants (both males and females) compared with young adults.29 One possible reason for this could be that MPT is influenced by many factors like testing conditions and number of trials, and hence it lacks reliability and validity.30,31 In nonsingers, only two studies have investigated the effect of aging on DSI and its related parameters. Hakkesteegt et al,5 investigated the effect of age and gender on DSI and its parameters. They found significant effect of age on DSI, F0-high, and I-low measures. However, gender had significant effect only on the MPT and F0-high measures. Recently, Goy et al,20 reported that older females had higher DSI values than younger females. However, there was no difference in the DSI values between young and older males. Few studies have documented the effect of aging on the singers’ acoustic measures of voice. The evidence from these studies suggests that singers even in their old age typically had stable SFF,32,33 significantly less jitter,34 greater intensity,34 and wider phonational ranges35 compared with nonsingers. However, there was no significant difference between older singers and nonsingers on shimmer and F0.34 Overall, most of the previous researches are focused on individual acoustic parameters, and haven’t studied the effect of aging in singers on DSI and its component parameters. Clearly, further data are needed to understand whether training in classical singing re-
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duces the effect of aging on DSI in singers compared with nonsingers. Hence, the aim of the present study was to compare DSI scores in trained Carnatic classical singers and nonsingers. The second purpose was to investigate the effect of aging on DSI and its parameters in singers and nonsingers. METHOD Participants Thirty female trained Carnatic classical singers participated in the present study. These thirty singers were subgrouped into two based on their age: 15 younger singers and 15 older singers. Younger singers were those individuals who were aged below fifty years and older singers were those who were aged above fifty years. The mean age of younger singers was 28.33 years (standard deviation [SD], 10.31; age range, 19–48 years). Their mean number of years of training was 19 years (SD, 6.88). Their mean duration of practice per day was 2.2 hours (SD, 1.89). Their mean body mass index (BMI) was 22.5 (SD, 2.47). The mean age of the older singers was 59.33 years (SD, 5.44; age range, 51–72 years). Their mean number of years of training was 35.26 years (SD, 7.21). Their mean duration of practice per day was 2.6 hours (SD, 1.24). Their mean BMI was 24.5 (SD, 3.24). At the time of recording all the singers were actively involved in vocal training. For comparison purposes, thirty age and gender matched nonsingers served as a control group. These nonsingers did not have any formal training in singing, including choral singing. Again, nonsingers were subdivided into 15 younger nonsingers and 15 older nonsingers. The mean age of younger nonsingers was 28.33 years (SD, 10.31; age range, 19–48 years). The mean age of older nonsingers was 58.93 years (SD, 4.77; age range, 51–68 years). The mean BMI for the younger nonsinger group was 21.1 (SD, 1.41). The mean BMI for the older nonsinger group was 23.6 (SD, 1.55). All the participants were recruited from Mysore, Karnataka, India. By taking detailed demographic history, participants were assessed for any speech, hearing, or neurological problems. Only those participants without any speech, hearing, or neurological problems were selected. Further, these participants did not have any medical conditions which could influence respiratory and phonatory functions. Hearing evaluation was done using calibrated clinical audiometer (Madsen Orbitor 922; GN Otometrics, Denmark) in a sound proofed room. All the participants had their air and bone conduction hearing thresholds less than 15 dBHL at octave frequencies 250 Hz to 8 kHz. Further, to check for any voice problem, a certified speech-language pathologist perceptually rated their voice quality using the GRBAS (grade, roughness, breathiness, asthenic, and strainness) scale.36 Both singers and nonsingers had normal voice quality. Instrumentation and recording procedure The recording was carried out in a sound-treated room using Ling Waves instrument (WEVOSYS, Germany). Ling Waves is a high quality software-hardware unit which analyses the human voice. Ling Waves comes with a sound level meter (SLM) with a microphone attached to it. The SLM was placed on a
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Comparing DSI of Carnatic Classical Singers and Nonsingers
tripod stand, and through this stand the SLM was adjusted to the patient’s mouth level. The Ling Waves software is a combined analysis tool for the measurement of the quantitative (singing/ voice range profile) and qualitative voice parameters. It consists of different modules. It has a separate module for the calculation of the DSI parameters. The noise level inside the room was less than 30 dB SPL (sound pressure level). As recommended by Ling Waves manual the participants were made to stand and do the following mentioned tasks. The microphone was adjusted according to the height of the participant. To avoid any distortions during the recording a distance of 30 cm was maintained between the microphone and the participant’s mouth. The participants were explained about the task and the second author demonstrated each task to the participants. The participants were given three trials for each task and the average was taken for each parameter. The following tasks were recorded from each participant. Tasks 1. Highest phonational frequency (F0-high): The participants were asked to phonate vowel /a/ from comfortable pitch to the highest pitch possible without any pitch breaks. They were also instructed not to use the false voice during the phonation. 2. Lowest intensity level (I-low): The participants were asked to sustain the vowel /a/ at a comfortable pitch from the softest loudness to the maximum loudness possible. In another way, the participant can start phonating at comfortable loudness and then slowly decrease the loudness level to the softest loudness they can go. 3. Jitter (%): The participants were instructed to produce sustained phonation of the vowel /a/ at a comfortable pitch and loudness for 2–3 seconds. The selected portion (2–3 seconds) of phonation was used for the jitter calculation. 4. Maximum phonation time (MPT): The participants were instructed to take a deep breath/inhale deeply and sustain vowel /a/ as long as possible at a comfortable pitch and loudness. The participants were instructed to use the maximum amount of air from their lung capacity.
Using the previously mentioned four parameters the DSI was calculated from the following formula: DSI ¼ 0:13 3 MPT ðsecondsÞ þ 0:0053 3 F0 high ðHzÞ 0:26 3 I low ðdBÞ 1:18 3 jitter ð%Þ þ 12:4 Statistical analysis Commercially available SPSS software (IBM, New York, NY) was used for statistical analysis. For the highest phonation frequency, the lowest intensity level, and MPT measures, analysis of variance (ANOVA) was completed with two levels of group (singers vs nonsingers) and two levels of age (younger vs older). An alpha level of 0.05 was selected. Post hoc analysis was done using independent sampled t test. For the DSI measure, as the standard deviation values were higher than the mean values for two groups (old singers and nonsingers), nonparametric Mann-Whitney U test was done. RESULTS Highest phonational frequency (F0-high) The results of two-way ANOVA for F0-high suggested significant main effects of group [F (1, 56) ¼ 119.761, P < 0.01] and age [F (1, 56) ¼ 93.317, P < 0.01]. Further, there was a significant interaction effect of groups versus age [F (1, 56) ¼ 21.840, P < 0.001]. Post hoc analysis using independent t test showed a significant difference between younger versus older participants for both singers [t (28) ¼ 8.439, P < 0.001] and nonsingers [t (28) ¼ 4.722, P < 0.001]. Further, a significant difference between singers versus nonsingers was found for both younger [t (28) ¼ 9.525, P < 0.001] and older [t (28) ¼ 5.474, P < 0.001] participants. Younger singers had significantly greater F0-high values compared with older singers. Further, both younger and older singers had significantly greater F0-high values compared with younger and older nonsingers (Table 1). Lowest intensity level (I-low in dB) The results of two-way ANOVA for the lowest intensity level suggested no significant main effect of group [F (1, 56) ¼ 0.031, P ¼ 0.861]. However, there was a significant main effect of age [F (1, 56) ¼ 10.446, P ¼ 0.002]. Younger
TABLE 1. Comparison of Means and SDs for the DSI and its Component Measures Between Younger and Older Carnatic Classical Singers and Nonsingers
Variable MPT (s) F0-high (Hz) I-low (dB) Jitter (%) DSI
Singers (Younger)
Singers (Older)
Nonsingers (Younger)
Nonsingers (Older)
(n ¼ 15)
(n ¼ 15)
(n ¼ 15)
(n ¼ 15)
15.58 (2.52) 982.15 (140.54) 54.92 (3.33) 0.155 (0.054) 5.16 (1.24)
11.01 (3.16) 595.79 (108.13) 61.90 (8.86) 0.130 (0.041) 0.744 (1.96)
12.95 (2.29) 561.19 (97.73) 57.62 (4.13) 0.175 (0.032) 1.82 (0.93)
10.058 (1.55) 426.77 (51.04) 59.70 (3.36) 0.146 (0.042) 0.27 (0.77)
Notes: SDs are provided in the parentheses.
68 participants (both singers and nonsingers) produced significantly lower intensity phonations compared with the older participants (Table 1). Nevertheless, there was no significant interaction effect between the group versus age [F (1, 56) ¼ 3.039, P ¼ 0.087]. Jitter (%) The results of two-way ANOVA for jitter (%) showed no significant main effect of group [F (1, 56) ¼ 2.519, P ¼ 0.118]. However, there was a significant main effect of age [F (1, 56) ¼ 5.853, P ¼ 0.019]. Younger participants (both singers and nonsingers) had significantly higher mean jitter values compared with the older participants (Table 1). Nevertheless, there was no significant interaction between groups versus age. Maximum phonation time (MPT in seconds) The results suggested a significant main effect of group (F (1, 56) ¼ 8.016, P ¼ 0.006) and age (F (1, 56) ¼ 34.731, P < 0.001). However, there was no significant interaction effect between groups versus age (F (1, 56) ¼ 1.733, P ¼ 0.193). Overall, singers had significantly longer MPT values compared with nonsingers (Table 1). Further, younger participants (both singers and nonsingers) had significantly longer MPT values compared with the older participants (both singers and nonsingers). Dysphonia severity index The results suggested statistically significant difference between singers versus nonsingers [U (56) ¼ 4.00, Z ¼ 3.208, P ¼ 0.001], and between younger versus older participants [U (56) ¼ 97.000, Z ¼ 5.219, P ¼ 0.000]. Post hoc analysis indicated significant difference between younger versus older participants for both singers [U (28) ¼ 2.000, Z ¼ 4.584, P ¼ 0.000] and nonsingers [U (28) ¼ 21.000, Z ¼ 3.796, P ¼ 0.000]. However, between singers versus nonsingers there was statistically significant difference only for younger participants {younger [U (28) ¼ 4.000, Z ¼ 4.501, P ¼ 0.00]; older [U (28) ¼ 78.000, Z ¼ 1.431, P ¼ 0.161]}. DISCUSSION The main purpose of the present study was to compare DSI values between trained Carnatic classical singers and nonsingers. The second purpose was to investigate the effect of age on DSI values in singers and nonsingers. Highest phonational frequency (F0-high) Carnatic classical singers (both younger and older) had significantly greater F0-high values compared with nonsingers (Table 1). Similar results are reported with Western Classical singers where greater F0-high values were found in both male and female singers compared with nonsingers.6 Using phonetogram, Awan 10 also reported greater F0-high values in trained singers compared with untrained singers. However, Brown et al,35 found statistically no significant difference between singers and nonsingers. Increased F0-high values in Carnatic classical singers compared with nonsingers may be because of training in singing. Like Western classical singing, Carnatic classical singers go through rigorous training for pitch matching,
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pitch gliding, and singing at different pitch (musical) scales. As a result of this training, singers may be able to produce greater frequency ranges and maximum frequencies than nonsingers. The results showed that F0-high values were significantly lower in older participants (both singers and nonsingers) compared with the younger participants. Reduced F0-high values in older nonsingers are consistent with previous studies.5,37 However, Goy et al,20 found no difference in F0high values between young and old females. The lowering of F0-high values with advancing age may be attributed to increase in the vocal fold edema, decrease in the elasticity of vocal folds, weakening of the intrinsic muscles, increase in the vocal fold mass, and ossification and calcification of the laryngeal cartilages.38,39 The significant decrease in the F0-high values in older singers compared with the younger singers suggests that the lowering of the highest phonational frequency is a biologically determined phenomenon and can occur even in the trained singers.35 Hence, Carnatic classical singers may need to adjust (lower) their ‘‘aadhaara shruthi’’ (base pitch) with aging. However, older singers’ F0-high values were still significantly greater than older nonsingers. This suggests that with aging structural changes in the vocal folds of singers may be characteristically different compared with nonsingers. Lowest intensity level (I-low) Statistically no significant difference was found between singers and nonsingers for I-Low values during phonation. The present results suggest that although Carnatic singers had slightly lower I-low values, they were similar to nonsingers. The present results are in contrast to previous findings in the literature,6,10,40 where they found significantly lower I-low values in Western singers compared with nonsingers. The reason for significantly lower I-low values in Western singers has been attributed to the effect of vocal training. With vocal training, singers are supposed to develop better abdominal support and greater control over their loudness ranges. Hence, they may be able to produce vocal intensities at lower levels. One another reason suggested is that training in Western classical singing includes specific respiratory and warm-up exercises for strengthening of abdominal muscles and diaphragm.6,41 Such systematic exercises for strengthening respiratory support are not present during training in Carnatic classical singing. Carnatic singing only emphasizes on singing at the right tonic pitch and tonal quality. Further, Carnatic singing is loud singing.14 Hence, the vocal folds may be more tuned to singing/phonating at louder voices compared with softer voices. Further studies need to be done to corroborate present findings. Younger individuals produced significantly lower intensity phonations compared with older individuals. Present results are in accordance with previous literature,5,37 and suggest that with aging there is reduced control over the breath support and phonatory abilities. This could be the reason for increased I-low values in older participants.5 Jitter (%) Overall, there was no significant difference between the singers and nonsingers for jitter (%) values (Table 1). Present results are
Santosh Maruthy and Preethi Ravibabu
Comparing DSI of Carnatic Classical Singers and Nonsingers
in contrast to study by Awan and Ensslen,6 who found that nonsingers had significantly higher jitter values compared with trained singers. Interestingly, in the present study, younger participants had significantly higher jitter values compared with the older participants. However, in both the groups of participants, jitter values were within the accepted normal limits (1%). It is reported that the values of jitter need to be viewed cautiously as multiple factors like the sound pressure level of phonation,42,43 mean fundamental frequency of phonation,44 health and fitness of participants can influence them. Hence, it is difficult to arrive at the firm conclusion about the effect of aging on jitter values. With increasing age, some previous studies have found increased jitter values,18,23–25,45 whereas few others have reported no changes in jitter values.5,20 Maximum phonation time (MPT) Singers had significantly longer MPT values compared with nonsingers (Table 1). MPT reflects coordination between breathing and phonation.46 So it was hypothesized that because of regular training, singers may have better coordination between two subsystems and hence longer MPT values. Early attempts to compare MPT values between singers and nonsingers have yielded inconsistent results. Caroll et al,47 found reduced MPT values in classically trained singers when compared with few selected previously published normative values. However, Awan and Ensslen6 reported no significant differences on MPT measures between trained and untrained vocalists. All the singers in the present study had at least 10 years of vocal training, and hence they may have better control over their respiratory support and glottal valving. The mean MPT values of younger individuals were significantly longer compared with older individuals, which is consistent with previous studies.5,26,27 Reduced MPT values in older individuals could be because of both structural and functional changes in respiratory and laryngeal systems with aging. Structural changes reported include reduced elasticity and muscle strength, increased stiffness in the thorax, loss of lung tissue elasticity, weakening of respiratory muscles, and degenerative changes in the laryngeal muscles.27,48,49 Functional changes reported include decreased elastic recoil forces of lung tissues, reduced vital capacity, increased residual volume, and reduced expiratory/inspiratory volume.50 When compared with Western norms, the mean MPT values in our participants (both singers and nonsingers) were significantly lower. According to Hirano,36 MPT values in normal males should be 34.6 seconds, and in females, 25.7 seconds. However, in Indian context, Jayakumar and Savithri15 found differences in the MPT values between the Indian and European population. They found MPT values to be 17.6 seconds for males and 13.8 seconds for females. This difference between Western data and Asian Indian data may be because of variation in the geographic and physical condition of individuals. The average Asian Indians are shorter and have less body mass compared with Caucasians.51 Further, they also have shorter and narrower chests compared with Caucasians.52 Because of this, their vital capacities and lung volumes are reduced compared with Caucasians.53–55 It is known that vital
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capacity and lung volumes significantly correlate with the MPT values,56 In India, the MPT values again vary between the singers and nonsingers group. Dysphonia severity index (DSI) The mean DSI values were significantly higher in younger singers compared with nonsingers (Table 1), which is consistent with Awan and Ensslen 6 findings. They also reported that the DSI values to be significantly higher in the trained vocalist group (6.35) compared with the untrained group (4.69). Timmerman, et al,57,58 found that the DSI values increased in the vocally trained group compared with the untrained group. The increase in DSI values in singers may be mainly because of the increased F0-high and longer MPT values which contributed to the overall increase in the DSI value. As the factorial influences of the components of the DSI were not done further studies need to be done to corroborate present claim. Further, when compared with Western classical singers, our singers had significantly lower DSI values. This difference may be mainly because of reduced MPT values in Carnatic classical singers compared with Western classical singers. The effect of age on DSI values were noted in both singers and nonsingers. Both younger singers and nonsingers had significantly greater DSI values compared with older singers and nonsingers respectively. This reduction in DSI values in older participants could be mainly because of lowering of F0high,5 and reduction in MPT values. As there is no significant difference between DSI values in old singers and nonsingers, it may be necessary to establish separate normative data for DSI values only for young singers. Collectively, in this study we found that Carnatic classical singing had a significant effect on DSI and two of its parameters (MPT and F0-high). Singers had significantly longer MPT, greater F0-high, and because of this higher DSI values. Age also had a significant effect on both singers and nonsingers. When compared with the younger participants, older participants had reduced MPT, F0-high, and DSI values. Results suggest that separate normative data may need to be established for singers and nonsingers for DSI and its parameters by taking age into consideration. As the sample size of singers and nonsingers was small further studies need to be done with a larger sample to corroborate present findings. Additionally, studies can also be taken up with male Carnatic classical singers to extend the current findings. Future studies are also needed to explore whether the significant difference noticed between singers and nonsingers could be mainly because of training or due to innate special abilities of singers. Acknowledgments The authors would like to thank Dr. S.R. Savithri, Director, All India institute of Speech and Hearing, Mysore, India, for allowing us to carry out this study. We also thank all the participants. REFERENCES 1. Wuyts FL, De Bodt MS, Molenberghs G, et al. The dysphonia severity index: an objective measure of vocal quality based on a multiparameter approach. J Speech Lang Hear Res. 2000;43:796–809.
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