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The effect of task on determination of maximum phonational frequency range
Journal of Voice
Vol. 14, No. 2, pp. 154-160 © 2000 Singular Publishing Group
The Effect of Task on Determination of Maximum Phonational Frequency Range * R i c h a r d I. Z r a i c k , t J u s t i n e L. N e l s o n , ; J a m e s C. M o n t a g u e , a n d * P a t r i c i a K. M o n o s o n *University of Arkansas for Medical Sciences, Little Rock, Arkansas; fPrivate Practice, Tampa Florida; ~University of Arkansas at Little Rock, Little Rock, Arkansas
Summary: The purpose of this study was to investigate if there was an effect of task on determination of maximum phonational frequency range (MPFR). Two tasks commonly used to elicit MPFR in clinical voice evaluations were compared. Normal adult females (N = 30) were examined. No statistically significant effect of task was found. Both tasks (glissando and discrete-step) were found to have a high positive correlation (0.84). Implications of the use of one task for determination of maximum phonational frequency range are discussed, as is the possibility of a task effect on determination of other voice parameters. Key Words: Pitch range--Maximum phonational frequency range--Voice evaluation--Voice therapy--Task effects.
Maximum phonational frequency range (MPFR) is defined by Hollien, et al ~ as "that range of vocal frequencies encompassing both the modal and falsetto registers; its extent is from the lowest tone sustainable in the modal register to the highest in falsetto, inclusive." Pulse (glottal fry) phonation has usually been excluded when defining MPFR because this phonatory mode is not used continuously during speech production. Loft or falsetto phonation, however, has been included in some definitions 2 even though loft phonation rarely (if ever) appears in normal speech. MPFR is one of the most frequently obtained voice measures. The widespread clinical use of
MPFR is confirmed by Hirano's 3 survey in which approximately 90% of the 276 respondents (speechlanguage pathologists, phoniatricians, and otolaryngologists) reported obtaining M P F R routinely during voice evaluations. The speech-language pathologists surveyed indicated the most frequent reasons for obtaining MPFR were to determine the degree of dysphonia and to monitor changes in phonatory ability. MPFR is regarded by many as the most easily definable and measurable parameter available in assessing the tone-generating capacity of the larynx and assessing the extent of laryngeal adjustment available during voice production.I, 4 Though MPFR is an indirect measure of laryngeal function during voice production, when it is used with other diagnostic measures as part of a comprehensive voice evaluation protocol, the results provide a composite picture of how the laryngeal, respiratory, resonatory, and psychological systems work together in voice production. 5
Accepted for publication October 4, 1999. Address correspondence and reprint requests to Richard I. Zraick, University of Arkansas for Medical Sciences, 4301 W. Markham Street, Mail Slot 722, Little Rock, AR 72205, USA. e-mail: zraickrichardi @exchange.uams.edu.
154
EFFECT OF TASK ON DETERMINATION OF MAXIMUM PHONATIONAL FREQUENCY RANGE MPFR data has been obtained for normal children, adults, and geriatric individuals,l,2,4, 6-15 as well as adults with laryngeal pathology, l 1,14,~5 and normal adults with laryngeal fatigue. 16 However, because there are no standardized methods for eliciting MPFR, comparisons of vocal function cannot be made across different voice clinics and across different periods of time. Therefore, several authors suggest establishing consistent methodology for elicitation of MPFR and other "tests of maximum performance.''2,12,15,17,18 Factors such as task or elicitation variables, instructions, and coaching provided to the patient and the number of trials allowed may affect determination of MPFR. Few studies have compared the methodology for eliciting MPFR. Reich et al 2,12 examined the effect of method of elicitation on MPFR in normal children and adults. In both studies, these investigators compared 5 elicitation methods (discrete-steps, slow steps, fast steps, slow glissando, and fast glissando) and found that the discrete-steps task yielded the smallest MPFR (in both hertz and semitones) compared to all other conditions. It should be noted that in both of the Reich et al studies 2,12 a pitchmatching procedure was used whereby subjects were required to match their productions to an audiotaped stimulus tone. Such a procedure has often been employed in investigations of MPFR, even though such a procedure is not likely to be used in routine clinical practice. Despite its leading to an underestimation of MPFR, the discrete-steps task has been used often to generate MPFR norms for adult speakers.l,8,9,~9, 20 A further review of the literature reveals variability in the task instruction provided by the examiner prior to the voicing task. No study was found that examined the effect of instructions provided to subjects during elicitation of MPFR. Reich et al 2,12 described a short training session provided prior to the trial, whereby the experimenters provided prompting, practice, and feedback during training sessions, but this was not compared to other instructional conditions. A common clinical procedure is to model behavior prior to its elicitation. 21 Review of the literature failed to identify a study in which the entire desired MPFR task was modeled prior to elicitation. Reich et al 2,12 provided subjects with a practice session
155
prior to the experimental task, and instructed the subject as to the type of breath required and the desired response prior to elicitation on all trials, but they did not measure the effect of modeling on the task. Modeling has been shown to influence other tests of maximum performance.21,22 Encouragement provided to the subjects during voicing tasks, also referred to as coaching, is an additional variable that may affect determination of MPFR. Reich et al 2 prompted subjects with a "hand-stepping" motion during discrete-step conditions and a "hand-sweeping" motion during the glissando conditions; however, the effects of coaching were not evaluated. Like modeling, coaching has also been shown to influence other tests of maximum performance. 2z-25 The precise influence of repeated trials on MPFR is also unknown. A common clinical procedure is to elicit MPFR with three trials, taking the largest MPFR to represent the subjects' range. When measuring the MPFR of children and adults, Reich et a12,12 obtained three measures of MPFR on each of the 5 tasks. Hollien et al 1 repeated MPFR trials until "both the experimenter and the subject were satisfied that the point had been reached which represented the subjects' lowest phonational frequencies." Although it is apparent that incorporating repeated trials can enhance tests of maximum performance,25 it is unclear just how many repeated trials is optimal. Clearly, the literature to date supports the notion that elicitation task, instructions, coaching, and the number of trials are variables that may influence determination of MPFR. As the first in a series of studies examining these variables, the purpose of this study is to examine the effect of elicitation task on the determination of the MPFR of normal adult females. In contrast to Reich et al, 2,12 only two tasks are chosen for comparison (glissando vs. discrete-step), and further, no pitch-matching procedure will be employed. These restrictions are purposeful and meant to approximate the typical clinical procedures used to elicit MPFR. It is believed that the results of this study will contribute to the growing literature suggesting a need for standardization of procedures for the elicitation of MPFR and other vocal parameters.
Journal of Voice, Vol. 14, No. 2, 2000
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RICHARD I. ZRAICK E T AL
METHOD Subjects Subjects were white females (N = 30) between the ages of 20.0 and 31.0 years (mean = 25.0 years). They were randomly selected from the undergraduate and graduate student population at the University of Arkansas at Little Rock, and met the following criteria: 1. No individual singing instruction or experience as a vocal soloist. 2. Hearing within normal limits as determined by pure-tone screening at 500, 1000, 2000, 4000, and 8000 Hz bilaterally at 20 dB HL. 3. Nonsmoking for the past 5 years. 4. Voice quality that was judged perceptually to be normal. This determination was made by two certified speech-language pathologists who are experienced voice clinicians. 5. Voice quality that was objectively determined to be normal. Using the Visi-Pitch II Voice Quality Assessment program (Kay Elemetrics Corp, Lincoln Park, New Jersey), only voices with a relative average perturbation (RAP) < 1.5% were included. 6. Normal vocal fold valving, that is, maximum phonation time (MPT) of at least 15 seconds. 7. Negative history of severe respiratory allergies, asthma, vocal fold pathology, or neuromotor impairment. 8. Language comprehension within normal limits. 9. Native speaker of English. Procedure All voice recordings and samples were obtained in the Speech and Voice Laboratory at the University of Arkansas at Little Rock. This room exhibits less than 10 dB sound pressure level (SPL) of ambient noise. Present in the room were the subject and the primary examiner (in all cases, the second author). Screening, training, and data collection took approximately 30 minutes per subject. Subjects first participated in an individual training session in which they were given written and verbal instructions for the MPFR task (see Appendix) and a full model of the task. This training session allowed subjects to become familiar with the task and provided them an opportunity to warm-up
Journal of Voice, Vol. 14, No. 2, 2000
their voice. It also allowed the experimenter to coach the subject, to maximize her performance during the data collection session. Vocal fatigue was not considered a factor, as subjects typically required only 3 to 4 practice trials to become familiar with the task. Furthermore, subjects were instructed to phonate at their most comfortable loudness, and this was monitored to ensure that they did not exceed 90 dB SPL. Following convention 1,2,8A°,~2the /a/vowel was used. Following Reich et al 2,12 verbal instructions were accompanied by "hand-stepping" motions during the discrete-step trials and "handsweeping" motions during glissando trials. Subjects were allowed to use the visual feedback from the Visi-Pitch II to augment their performance. The data collection session immediately followed the training session and was held in the same room as the training session, with the second author again as primary experimenter. Subjects performed each task (glissando and discrete-steps) 3 times for a total of 12 responses (2 conditions × 6 attempts). The order of elicitation of MPFR was randomized so that each experimental condition consisted of 15 subjects using the glissando task first and 15 subjects using the discrete-step task first. Within each condition, subjects were always instructed to first demonstrate their maximum fundamental frequency (F0) (three consecutive trials), then their minimum (F0) was elicited (three consecutive trials). Subjects were allowed a 1-minute rest period between MPFR attempts. The maximum F 0 and minimum F 0 were determined from the digital readout accompanying the frequency-versus-time waveform displayed on the monitor. The maximum F 0 and the minimum F 0 were defined as the subject's highest and lowest/o/ sustained for at least 0.5 seconds. Vocalizations characterized by experimenter-perceived vocal quality deterioration, and/or excessive perturbation (RAP > 1.5%) were excluded from consideration. Four dependent measures were ultimately derived from each subject's performance: (1) maximum F 0 (the highest F 0 of the three upward trials); (2) minimum F 0 (the lowest F 0 of the three downward trials); (3) MPFR: hertz (maximum F 0 minus minimum F 0 ); and (4) MPFR: semitones (MPFR: hertz converted to ST).
EFFECT OF TASK ON DETERMINATION OF MAXIMUM PHONATIONAL FREQUENCY RANGE RESULTS
157
Table 3 presents in hertz the mean, SD, and range for the glissando versus discrete-step conditions. The mean for the glissando condition was 1030.73 Hz (SD = 180.07 Hz) and the discrete-steps condition was 1005.82 Hz (SD = 158.57 Hz). A paired t-test was again used to compare the means (in Hz) for the two conditions, and is reported in Table 4. The observed t-test results (t = 1.39) did not reveal a statistically significant difference between the glissando and discrete-step conditions, and again there was a high positive correlation (0.84, P < 0.001) between the ranges (in Hz) obtained for the glissando and discrete-step conditions.
Table 1 displays in semitones (ST) the mean, standard deviation, and range for the glissando versus discrete-step conditions. The mean for the glissando condition was 34.4 ST (standard deviation [SD] = 3.7 ST) and the mean for the discrete-steps condition was 34.2 st (SD = 2.8 ST). M P F R for the subjects extended from nearly 2l/2 octaves (26.43 ST) to 31/2 octaves (42.03 ST) for both conditions. A paired t-test was used to assess the effects of method of elicitation (glissando vs. discrete-step) and is reported in Table 2. The observed t-test results (t = 0.665) did not reveal a statistically significant difference between the glissando and discretestep conditions. There was a high positive correlation (0.84, P < 0.001) between the ranges (in ST) obtained for the glissando and discrete-step conditions.
DISCUSSION This study sought to examine if elicitation task had a significant effect on the determination of
TABLE 1. Mean, Standard Deviation, and Range (in Semitones)for the Glissando and Discrete-Step Conditions Jbr all Subjects (N = 30) Condition
N
Mean
SD
Range
Glissando
30
34.4
3.7
28.51-42.03
Discrete-step
30
34.2
2.8
29.91-40.31
TABLE 2. Paired T-Test Results (in Semitones)for the Glissando and Discrete-step Conditions for All Subjects (N = 30) Paired Differences 95% Confidence Interval of the Difference
Glissando-step
Nonsignnificant Probability
Mean
SD
SEM
Lower
Upper
t-Value
df
(Two-tailed)
0.24
2.01
0.37
-0.5073
0.9960
0.665
29
0.511
TABLE 3. Mean, Standard Deviation, and Range (in Hertz)for the Glissando and Discrete-Step Conditions for all Subjects (N = 30) Condition
N
Mean
SD
Range
Glissando
30
1030.73
180.07 738.48-1329.74
Discrete-step
30
1005.82
158.57 761.46-1327.32 Journal of Voice, Vol. 14, No. 2, 2000
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RICHARD L ZRAICK E T A L T A B L E 4. Paired T-Test Results (in Semitones)for the Glissando and Discrete-step Conditions
for All Subjects (N = 30) Paired Differences 95% Confidence Interval of the Difference Mean
SD
24.9
98.33
Glissando-step
SEM
Lower
Upper
t-Value
df
(Two-tailed)
17.95
-11.81
61.62
1.39
29
0.176
MPFR of young adult females with normal voice quality. The results of the present study indicate that there is not a statistically significant effect of task (P < 0.001). That is, for the population under investigation, it appears that both elicitation tasks (discrete-steps and glissando) yield similar results. These results are not consistent with those of Reich et a12,12 who compared 5 MPFR elicitation procedures (discrete-steps, slow steps, fast steps, slow glissando, and fast glissando) in children and adults of both genders. Reich et al 2,12 found that the discrete-steps yielded a significantly smaller MPFR than all other conditions for both children and adults. For their adult female subjects, Reich et al 2 obtained a mean MPFR of 32.0 ST (836.6 Hz) for the discrete-steps condition and 34.5 ST (975.3 Hz) for the fast glissando condition. However, it should be noted that Reich et al 2 excluded productions in the falsetto register, while our methodology included falsetto productions. It should also be noted that Reich et al 2 used a pitch-matching procedure--such a procedure was not used in this study. In routine clinical application, a pitch-matching procedure would not typically be used. Although such methodological differences make it difficult to compare absolute MPFR values across these two studies, it does not preclude analysis of the similarity of elicitation conditions within each study. Reich et al 2 reported a difference of 2.5 ST between the glissand o and discrete-steps conditions, with discrete-steps yielding the smaller MPFR. In the current study, the discrete-steps condition yielded the smaller MPFR, but there was only a 0.2 ST difference between the two conditions. Subjects in the present study may have been more apt to attempt a higher pitch during the discrete-steps condition because they did not feel pressure to match a i
Journal of Voice, Vol. 14, No. 2, 2000
Nonsignnificant Probability
stimulus tone. Also, the effect of coaching and pra c tice cannot be underestimated in the present study, nor can the use of visual feedback from the VisiPitch II. All subjects reported using the visual feedback to augment their performance. Although Reich et al 2 attributed the inferior performance of the discrete-steps to an "expiratory continuity" phenomenon, we did not find this phenomenon to be a primary factor in our investigation. Our results are also not consistent with Hollien et al,l who obtained MPFR normative data on female adults, using a discrete-steps task to match the pitch of a stimulus tone. These investigators reported a mean MPFR of 37.0 ST (range = 23-50 ST); both these measures of central tendency are greater than those reported in the present investigation (mean = 34.2 ST, range = 30-40 ST). However, Hollien et al 1 repeated MPFR trials until "both the experimenter and the subject were satisfied that the point had been reached which represented the subjects' lowest phonational frequencies." This is an important methodological difference from the present study, where only three elicitation trials were allowed. Furthermore, the Hollien et al 1 study examined a considerably larger pool of subjects (N = 202) than the present study. Therefore, it is difficult to compare absolute MPFR values from these two studies. Because of the methodological differences between the present study and both Reich et al 2,12 and Hollien et al, 1 it is perhaps more useful to discuss the direct clinical implications of the present study. Clearly, for the population under investigation, with the methodology employed, there is no significant difference in MPFR obtained via the discrete versus glissando task. No statistically significant difference between the two tasks may in fact be a clinically important finding.
EFFECT OF TASK ON DETERMINATION OF MAXIMUM PHONATIONAL FREQUENCY RANGE In routine clinical practice, both the discrete and glissando tasks enjoy prominence and are likely to be within the diagnostic arsenal of the average clinician. Likewise, the methodology employed in the present study was designed to approximate the typical clinical diagnostic protocol by avoiding the use of potentially cumbersome pitch-matching tasks. For both the patient and the clinician, use of simple elicitation tasks in a simple procedure may facilitate obtaining MPFR. Based on the results of this limited study, voice clinicians can now have some assurance that the resulting MPFR obtained via the simple discrete-steps task is not significantly different than the MPFR obtained via the alternative (glissando) task. Directions for future research stem from the limitations of the present study. A relatively small number of young female subjects from a restricted population were investigated, thus limiting the generalizability of the findings to other populations of interest (eg, females of other ages, males of any age, trained singers, voice-disordered subjects, etc). Likewise, the methodology could be expanded to include other tasks for eliciting MPFR. For example, one may compare two other routine methods (basal-to-ceiling and vice versa) to the mid-to-basal and mid-to-ceiling methods employed in this study. Lastly, other variables related to practice, coaching, and instruction could be investigated to determine their effect on determination of MPFR.
Acknowledgments: This paper is based in part on a thesis completed by the second author, under the direction of the first author. Thanks to Dr. Doug Buffalo at the University of Arkansas at Little Rock for statistical consulting. APPENDIX: INSTRUCTIONS FOR THE GLISSANDO AND DISCRETE-STEP TASKS
Task I: Glissando I want you to take a deep breath then produce/a/ starting at ~/comfortable pitch and loudness level and going to the highest note you can make in one breath. Move from one note to the next without stopping your voice like this (give a full model using the Visi-Pitch). Keep moving up the scale until
159
you feel like you can't go any higher. When you feel like you're reaching the top of your range try to hold the notes for 2 seconds. Watch the screen to see how high you are getting and how long you are holding the sound. Remember to take your deepest breath, start at a comfortable pitch, and go up as high as you can into falsetto. I want you to take a deep breath then produce/a/ starting at a comfortable pitch and loudness level and going to the lowest note you can make in one breath. Move from one note to the next without stopping your voice like this (give a full model using the Visi-Pitch). Keep moving down the scale until you feel like you can't make a lower sound. When you feel like you're reaching the bottom of your range try to hold the notes for 2 seconds. Watch the screen to see how low you are getting and how long you are holding the sound. Remember to take your deepest breath, start at a comfortable pitch, and go down as low as you can into glottal fry.
Task Ih Discrete steps I want you to take a deep breath and produce/a/ at a comfortable pitch and loudness level. Before moving up to the next note, I would like you to take a short breath in between. These short breaths between the notes will show up on the bottom of the Visi-Pitch as a flat blue line. I will give you an example (give full model and point out the breaths between each step as shown on the Visi-Pitch). Keep Stepping up the scale until you feel like you can't make a higher sound. When you feel like you're reaching the top of your range try to hold the notes for 2 seconds. Watch the screen to see how high you are getting and how long you are holding the sound. Remember to take your deepest breath, start at a comfortable pitch, and go high as high as you can into falsetto. I want you to {ake a deep breath and p r o d u c e / d at a comfortable pitch and loudness level. Before moving down to the next note, I would like you to take a short breath in between. These short breaths between th e notes will show up on the bottom of the Vis~-Pitch as a flat blue line. I will give you an example (give futt model and point out the breaths between each step as shown on the Visi=Pitch). Keep stepping up the scale until you feel like you can't :
Journal of Voice, Vol. 14, No, 2, 2000
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RICHARD L ZRAICK E T AL
make a lower sound. When you feel like you're reaching the bottom of your range try to hold the notes for 2 seconds. Watch the screen to see how low you are getting and how long you are holding the sound. Remember to take your deepest breath, start at a comfortable pitch, and go as low as you can into glottal fry.
REFERENCES 1. Hollien H, Dew D, Philips E Data on adult phonational ranges. J Speech Hear Res. 1971;14:755-760. 2. Reich AR, Mason, JA, Frederickson, RR, Schlauch, RS. Methodological variables affecting phonational frequency range in adults. J Speech Hear Dis. 1990;55:124-131. 3. Hirano M. Objective evaluation of the human voice: clinical aspects. Folia Phoniatr. 1989;41:89-144. 4. Awan SN. Phonetographic profiles and F0-SPL characteristics of untrained versus trained vocal groups. J Voice. 1991;5:41-50. 5. Stemple JC. Voice research: so what? A clearer view of voice production. J Voice. 1993;7:293-300. 6. Ptacek PH, Sander E, Maloney WH, Jackson CR. Phonatory and related changes with advanced age. J Speech Hear Res. 1966;9:535-560. 7. Shipp T, McGlone RE. Laryngeal dynamics associated with voice frequency change. J Speech Hear Res. 1971;14:761-769. 8. Colton RH, Hollien H. Phonational range in the modal and falsetto registers. J Speech Hear Res. 1972;15:708-713. 9. Coleman RE Mabis JH, Hinson JK. Fundamental frequenc y - s o u n d pressure level profiles of adult male and female voices. J Speech Hear Res. 1977;20:197-204. 10. Coleman RF, Mott JB. Fundamental frequency and sound pressure level profiles of young female singers. Folia Phoniatr. 1978;30:94-102. 11. Ramig LA, Ringel RL. Effects of physiological aging on selected acoustic characteristics of voice. J Speech Hear Res. 1983;26:22-30.
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12. Reich AR, Mason JA, Frederickson RR, Schlauch RS. Factors influencing fundamental frequency range estimates in children. J Speech Hear Dis. 1989;54:429-438. 13. Britto AI, Doyle PC. A comparison of habitual and derived optimal voice fundamental frequency values in normal young adult speakers. J Speech HearDisord. 1990;55:476484. 14. Canter GJ. Speech characteristics of patients with Parkinson's disease: II. Physiological support for speech. J Speech Hear Disord. 1965;30:44-49. 15. Hirano M, Tanaka S, Fujita M, Terasawa R. Fundamental frequency and sound pressure level of phonation in pathological states. J Voice. 1991;5:120-127. 16. Kitch JA, Oates J, Greenwood K. Performance effects on the voices of l0 choral tenors, acoustic and perceptual findings. J Voice. 1996; 10:217-227. 17. Kent RD, Kent JF, Rosenbek JC. Maximum performance tests of speech production. J Speech Hear Disord. 1987; 52:367-387. 18. Bless DM, Baken RJ. Assessment of voice. J Voice. 1992;6:95-97. 19. Hollien H, Michel JE Vocal fry as a phonational register. J Speech Hear Res. 1968; 11:600-604. 20. Hollien H. The registers and ranges of the voice. In: Cooper M, Cooper MH, eds. Approaches to Vocal Rehabilitation. Springfield, Ill: Charles C. Thomas; 1977:76-121. 21. Neiman GS, Edeson B. Procedural aspects of eliciting maximum phonation time. Folia PhoniatrLogop. 1981;33: 285-293. 22. Soman B. The effect of variations in method of elicitation on maximum sustained phoneme duration. J Voice. 1977;11:285-294. 23. Reich AR, Mason JA, Polen SB. Task administration variables affecting phonation-time measures in third-grade girls with normal voice quality. Lang, Speech, Hear Services in Schools. 1986;17:262-269. 24. Brown WS, Morris RJ, Hicks DM, Howell E. Phonational profiles of female professional singers and nonsingers. J Voice. 1993;7:219-226. 25. Finnegan DE. Maximum phonation time for children with normal voices. J Commun Disord. 1984;17:309-317.
Vol. 14, No. 2, pp. 154-160 © 2000 Singular Publishing Group
The Effect of Task on Determination of Maximum Phonational Frequency Range * R i c h a r d I. Z r a i c k , t J u s t i n e L. N e l s o n , ; J a m e s C. M o n t a g u e , a n d * P a t r i c i a K. M o n o s o n *University of Arkansas for Medical Sciences, Little Rock, Arkansas; fPrivate Practice, Tampa Florida; ~University of Arkansas at Little Rock, Little Rock, Arkansas
Summary: The purpose of this study was to investigate if there was an effect of task on determination of maximum phonational frequency range (MPFR). Two tasks commonly used to elicit MPFR in clinical voice evaluations were compared. Normal adult females (N = 30) were examined. No statistically significant effect of task was found. Both tasks (glissando and discrete-step) were found to have a high positive correlation (0.84). Implications of the use of one task for determination of maximum phonational frequency range are discussed, as is the possibility of a task effect on determination of other voice parameters. Key Words: Pitch range--Maximum phonational frequency range--Voice evaluation--Voice therapy--Task effects.
Maximum phonational frequency range (MPFR) is defined by Hollien, et al ~ as "that range of vocal frequencies encompassing both the modal and falsetto registers; its extent is from the lowest tone sustainable in the modal register to the highest in falsetto, inclusive." Pulse (glottal fry) phonation has usually been excluded when defining MPFR because this phonatory mode is not used continuously during speech production. Loft or falsetto phonation, however, has been included in some definitions 2 even though loft phonation rarely (if ever) appears in normal speech. MPFR is one of the most frequently obtained voice measures. The widespread clinical use of
MPFR is confirmed by Hirano's 3 survey in which approximately 90% of the 276 respondents (speechlanguage pathologists, phoniatricians, and otolaryngologists) reported obtaining M P F R routinely during voice evaluations. The speech-language pathologists surveyed indicated the most frequent reasons for obtaining MPFR were to determine the degree of dysphonia and to monitor changes in phonatory ability. MPFR is regarded by many as the most easily definable and measurable parameter available in assessing the tone-generating capacity of the larynx and assessing the extent of laryngeal adjustment available during voice production.I, 4 Though MPFR is an indirect measure of laryngeal function during voice production, when it is used with other diagnostic measures as part of a comprehensive voice evaluation protocol, the results provide a composite picture of how the laryngeal, respiratory, resonatory, and psychological systems work together in voice production. 5
Accepted for publication October 4, 1999. Address correspondence and reprint requests to Richard I. Zraick, University of Arkansas for Medical Sciences, 4301 W. Markham Street, Mail Slot 722, Little Rock, AR 72205, USA. e-mail: zraickrichardi @exchange.uams.edu.
154
EFFECT OF TASK ON DETERMINATION OF MAXIMUM PHONATIONAL FREQUENCY RANGE MPFR data has been obtained for normal children, adults, and geriatric individuals,l,2,4, 6-15 as well as adults with laryngeal pathology, l 1,14,~5 and normal adults with laryngeal fatigue. 16 However, because there are no standardized methods for eliciting MPFR, comparisons of vocal function cannot be made across different voice clinics and across different periods of time. Therefore, several authors suggest establishing consistent methodology for elicitation of MPFR and other "tests of maximum performance.''2,12,15,17,18 Factors such as task or elicitation variables, instructions, and coaching provided to the patient and the number of trials allowed may affect determination of MPFR. Few studies have compared the methodology for eliciting MPFR. Reich et al 2,12 examined the effect of method of elicitation on MPFR in normal children and adults. In both studies, these investigators compared 5 elicitation methods (discrete-steps, slow steps, fast steps, slow glissando, and fast glissando) and found that the discrete-steps task yielded the smallest MPFR (in both hertz and semitones) compared to all other conditions. It should be noted that in both of the Reich et al studies 2,12 a pitchmatching procedure was used whereby subjects were required to match their productions to an audiotaped stimulus tone. Such a procedure has often been employed in investigations of MPFR, even though such a procedure is not likely to be used in routine clinical practice. Despite its leading to an underestimation of MPFR, the discrete-steps task has been used often to generate MPFR norms for adult speakers.l,8,9,~9, 20 A further review of the literature reveals variability in the task instruction provided by the examiner prior to the voicing task. No study was found that examined the effect of instructions provided to subjects during elicitation of MPFR. Reich et al 2,12 described a short training session provided prior to the trial, whereby the experimenters provided prompting, practice, and feedback during training sessions, but this was not compared to other instructional conditions. A common clinical procedure is to model behavior prior to its elicitation. 21 Review of the literature failed to identify a study in which the entire desired MPFR task was modeled prior to elicitation. Reich et al 2,12 provided subjects with a practice session
155
prior to the experimental task, and instructed the subject as to the type of breath required and the desired response prior to elicitation on all trials, but they did not measure the effect of modeling on the task. Modeling has been shown to influence other tests of maximum performance.21,22 Encouragement provided to the subjects during voicing tasks, also referred to as coaching, is an additional variable that may affect determination of MPFR. Reich et al 2 prompted subjects with a "hand-stepping" motion during discrete-step conditions and a "hand-sweeping" motion during the glissando conditions; however, the effects of coaching were not evaluated. Like modeling, coaching has also been shown to influence other tests of maximum performance. 2z-25 The precise influence of repeated trials on MPFR is also unknown. A common clinical procedure is to elicit MPFR with three trials, taking the largest MPFR to represent the subjects' range. When measuring the MPFR of children and adults, Reich et a12,12 obtained three measures of MPFR on each of the 5 tasks. Hollien et al 1 repeated MPFR trials until "both the experimenter and the subject were satisfied that the point had been reached which represented the subjects' lowest phonational frequencies." Although it is apparent that incorporating repeated trials can enhance tests of maximum performance,25 it is unclear just how many repeated trials is optimal. Clearly, the literature to date supports the notion that elicitation task, instructions, coaching, and the number of trials are variables that may influence determination of MPFR. As the first in a series of studies examining these variables, the purpose of this study is to examine the effect of elicitation task on the determination of the MPFR of normal adult females. In contrast to Reich et al, 2,12 only two tasks are chosen for comparison (glissando vs. discrete-step), and further, no pitch-matching procedure will be employed. These restrictions are purposeful and meant to approximate the typical clinical procedures used to elicit MPFR. It is believed that the results of this study will contribute to the growing literature suggesting a need for standardization of procedures for the elicitation of MPFR and other vocal parameters.
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METHOD Subjects Subjects were white females (N = 30) between the ages of 20.0 and 31.0 years (mean = 25.0 years). They were randomly selected from the undergraduate and graduate student population at the University of Arkansas at Little Rock, and met the following criteria: 1. No individual singing instruction or experience as a vocal soloist. 2. Hearing within normal limits as determined by pure-tone screening at 500, 1000, 2000, 4000, and 8000 Hz bilaterally at 20 dB HL. 3. Nonsmoking for the past 5 years. 4. Voice quality that was judged perceptually to be normal. This determination was made by two certified speech-language pathologists who are experienced voice clinicians. 5. Voice quality that was objectively determined to be normal. Using the Visi-Pitch II Voice Quality Assessment program (Kay Elemetrics Corp, Lincoln Park, New Jersey), only voices with a relative average perturbation (RAP) < 1.5% were included. 6. Normal vocal fold valving, that is, maximum phonation time (MPT) of at least 15 seconds. 7. Negative history of severe respiratory allergies, asthma, vocal fold pathology, or neuromotor impairment. 8. Language comprehension within normal limits. 9. Native speaker of English. Procedure All voice recordings and samples were obtained in the Speech and Voice Laboratory at the University of Arkansas at Little Rock. This room exhibits less than 10 dB sound pressure level (SPL) of ambient noise. Present in the room were the subject and the primary examiner (in all cases, the second author). Screening, training, and data collection took approximately 30 minutes per subject. Subjects first participated in an individual training session in which they were given written and verbal instructions for the MPFR task (see Appendix) and a full model of the task. This training session allowed subjects to become familiar with the task and provided them an opportunity to warm-up
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their voice. It also allowed the experimenter to coach the subject, to maximize her performance during the data collection session. Vocal fatigue was not considered a factor, as subjects typically required only 3 to 4 practice trials to become familiar with the task. Furthermore, subjects were instructed to phonate at their most comfortable loudness, and this was monitored to ensure that they did not exceed 90 dB SPL. Following convention 1,2,8A°,~2the /a/vowel was used. Following Reich et al 2,12 verbal instructions were accompanied by "hand-stepping" motions during the discrete-step trials and "handsweeping" motions during glissando trials. Subjects were allowed to use the visual feedback from the Visi-Pitch II to augment their performance. The data collection session immediately followed the training session and was held in the same room as the training session, with the second author again as primary experimenter. Subjects performed each task (glissando and discrete-steps) 3 times for a total of 12 responses (2 conditions × 6 attempts). The order of elicitation of MPFR was randomized so that each experimental condition consisted of 15 subjects using the glissando task first and 15 subjects using the discrete-step task first. Within each condition, subjects were always instructed to first demonstrate their maximum fundamental frequency (F0) (three consecutive trials), then their minimum (F0) was elicited (three consecutive trials). Subjects were allowed a 1-minute rest period between MPFR attempts. The maximum F 0 and minimum F 0 were determined from the digital readout accompanying the frequency-versus-time waveform displayed on the monitor. The maximum F 0 and the minimum F 0 were defined as the subject's highest and lowest/o/ sustained for at least 0.5 seconds. Vocalizations characterized by experimenter-perceived vocal quality deterioration, and/or excessive perturbation (RAP > 1.5%) were excluded from consideration. Four dependent measures were ultimately derived from each subject's performance: (1) maximum F 0 (the highest F 0 of the three upward trials); (2) minimum F 0 (the lowest F 0 of the three downward trials); (3) MPFR: hertz (maximum F 0 minus minimum F 0 ); and (4) MPFR: semitones (MPFR: hertz converted to ST).
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Table 3 presents in hertz the mean, SD, and range for the glissando versus discrete-step conditions. The mean for the glissando condition was 1030.73 Hz (SD = 180.07 Hz) and the discrete-steps condition was 1005.82 Hz (SD = 158.57 Hz). A paired t-test was again used to compare the means (in Hz) for the two conditions, and is reported in Table 4. The observed t-test results (t = 1.39) did not reveal a statistically significant difference between the glissando and discrete-step conditions, and again there was a high positive correlation (0.84, P < 0.001) between the ranges (in Hz) obtained for the glissando and discrete-step conditions.
Table 1 displays in semitones (ST) the mean, standard deviation, and range for the glissando versus discrete-step conditions. The mean for the glissando condition was 34.4 ST (standard deviation [SD] = 3.7 ST) and the mean for the discrete-steps condition was 34.2 st (SD = 2.8 ST). M P F R for the subjects extended from nearly 2l/2 octaves (26.43 ST) to 31/2 octaves (42.03 ST) for both conditions. A paired t-test was used to assess the effects of method of elicitation (glissando vs. discrete-step) and is reported in Table 2. The observed t-test results (t = 0.665) did not reveal a statistically significant difference between the glissando and discretestep conditions. There was a high positive correlation (0.84, P < 0.001) between the ranges (in ST) obtained for the glissando and discrete-step conditions.
DISCUSSION This study sought to examine if elicitation task had a significant effect on the determination of
TABLE 1. Mean, Standard Deviation, and Range (in Semitones)for the Glissando and Discrete-Step Conditions Jbr all Subjects (N = 30) Condition
N
Mean
SD
Range
Glissando
30
34.4
3.7
28.51-42.03
Discrete-step
30
34.2
2.8
29.91-40.31
TABLE 2. Paired T-Test Results (in Semitones)for the Glissando and Discrete-step Conditions for All Subjects (N = 30) Paired Differences 95% Confidence Interval of the Difference
Glissando-step
Nonsignnificant Probability
Mean
SD
SEM
Lower
Upper
t-Value
df
(Two-tailed)
0.24
2.01
0.37
-0.5073
0.9960
0.665
29
0.511
TABLE 3. Mean, Standard Deviation, and Range (in Hertz)for the Glissando and Discrete-Step Conditions for all Subjects (N = 30) Condition
N
Mean
SD
Range
Glissando
30
1030.73
180.07 738.48-1329.74
Discrete-step
30
1005.82
158.57 761.46-1327.32 Journal of Voice, Vol. 14, No. 2, 2000
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RICHARD L ZRAICK E T A L T A B L E 4. Paired T-Test Results (in Semitones)for the Glissando and Discrete-step Conditions
for All Subjects (N = 30) Paired Differences 95% Confidence Interval of the Difference Mean
SD
24.9
98.33
Glissando-step
SEM
Lower
Upper
t-Value
df
(Two-tailed)
17.95
-11.81
61.62
1.39
29
0.176
MPFR of young adult females with normal voice quality. The results of the present study indicate that there is not a statistically significant effect of task (P < 0.001). That is, for the population under investigation, it appears that both elicitation tasks (discrete-steps and glissando) yield similar results. These results are not consistent with those of Reich et a12,12 who compared 5 MPFR elicitation procedures (discrete-steps, slow steps, fast steps, slow glissando, and fast glissando) in children and adults of both genders. Reich et al 2,12 found that the discrete-steps yielded a significantly smaller MPFR than all other conditions for both children and adults. For their adult female subjects, Reich et al 2 obtained a mean MPFR of 32.0 ST (836.6 Hz) for the discrete-steps condition and 34.5 ST (975.3 Hz) for the fast glissando condition. However, it should be noted that Reich et al 2 excluded productions in the falsetto register, while our methodology included falsetto productions. It should also be noted that Reich et al 2 used a pitch-matching procedure--such a procedure was not used in this study. In routine clinical application, a pitch-matching procedure would not typically be used. Although such methodological differences make it difficult to compare absolute MPFR values across these two studies, it does not preclude analysis of the similarity of elicitation conditions within each study. Reich et al 2 reported a difference of 2.5 ST between the glissand o and discrete-steps conditions, with discrete-steps yielding the smaller MPFR. In the current study, the discrete-steps condition yielded the smaller MPFR, but there was only a 0.2 ST difference between the two conditions. Subjects in the present study may have been more apt to attempt a higher pitch during the discrete-steps condition because they did not feel pressure to match a i
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Nonsignnificant Probability
stimulus tone. Also, the effect of coaching and pra c tice cannot be underestimated in the present study, nor can the use of visual feedback from the VisiPitch II. All subjects reported using the visual feedback to augment their performance. Although Reich et al 2 attributed the inferior performance of the discrete-steps to an "expiratory continuity" phenomenon, we did not find this phenomenon to be a primary factor in our investigation. Our results are also not consistent with Hollien et al,l who obtained MPFR normative data on female adults, using a discrete-steps task to match the pitch of a stimulus tone. These investigators reported a mean MPFR of 37.0 ST (range = 23-50 ST); both these measures of central tendency are greater than those reported in the present investigation (mean = 34.2 ST, range = 30-40 ST). However, Hollien et al 1 repeated MPFR trials until "both the experimenter and the subject were satisfied that the point had been reached which represented the subjects' lowest phonational frequencies." This is an important methodological difference from the present study, where only three elicitation trials were allowed. Furthermore, the Hollien et al 1 study examined a considerably larger pool of subjects (N = 202) than the present study. Therefore, it is difficult to compare absolute MPFR values from these two studies. Because of the methodological differences between the present study and both Reich et al 2,12 and Hollien et al, 1 it is perhaps more useful to discuss the direct clinical implications of the present study. Clearly, for the population under investigation, with the methodology employed, there is no significant difference in MPFR obtained via the discrete versus glissando task. No statistically significant difference between the two tasks may in fact be a clinically important finding.
EFFECT OF TASK ON DETERMINATION OF MAXIMUM PHONATIONAL FREQUENCY RANGE In routine clinical practice, both the discrete and glissando tasks enjoy prominence and are likely to be within the diagnostic arsenal of the average clinician. Likewise, the methodology employed in the present study was designed to approximate the typical clinical diagnostic protocol by avoiding the use of potentially cumbersome pitch-matching tasks. For both the patient and the clinician, use of simple elicitation tasks in a simple procedure may facilitate obtaining MPFR. Based on the results of this limited study, voice clinicians can now have some assurance that the resulting MPFR obtained via the simple discrete-steps task is not significantly different than the MPFR obtained via the alternative (glissando) task. Directions for future research stem from the limitations of the present study. A relatively small number of young female subjects from a restricted population were investigated, thus limiting the generalizability of the findings to other populations of interest (eg, females of other ages, males of any age, trained singers, voice-disordered subjects, etc). Likewise, the methodology could be expanded to include other tasks for eliciting MPFR. For example, one may compare two other routine methods (basal-to-ceiling and vice versa) to the mid-to-basal and mid-to-ceiling methods employed in this study. Lastly, other variables related to practice, coaching, and instruction could be investigated to determine their effect on determination of MPFR.
Acknowledgments: This paper is based in part on a thesis completed by the second author, under the direction of the first author. Thanks to Dr. Doug Buffalo at the University of Arkansas at Little Rock for statistical consulting. APPENDIX: INSTRUCTIONS FOR THE GLISSANDO AND DISCRETE-STEP TASKS
Task I: Glissando I want you to take a deep breath then produce/a/ starting at ~/comfortable pitch and loudness level and going to the highest note you can make in one breath. Move from one note to the next without stopping your voice like this (give a full model using the Visi-Pitch). Keep moving up the scale until
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you feel like you can't go any higher. When you feel like you're reaching the top of your range try to hold the notes for 2 seconds. Watch the screen to see how high you are getting and how long you are holding the sound. Remember to take your deepest breath, start at a comfortable pitch, and go up as high as you can into falsetto. I want you to take a deep breath then produce/a/ starting at a comfortable pitch and loudness level and going to the lowest note you can make in one breath. Move from one note to the next without stopping your voice like this (give a full model using the Visi-Pitch). Keep moving down the scale until you feel like you can't make a lower sound. When you feel like you're reaching the bottom of your range try to hold the notes for 2 seconds. Watch the screen to see how low you are getting and how long you are holding the sound. Remember to take your deepest breath, start at a comfortable pitch, and go down as low as you can into glottal fry.
Task Ih Discrete steps I want you to take a deep breath and produce/a/ at a comfortable pitch and loudness level. Before moving up to the next note, I would like you to take a short breath in between. These short breaths between the notes will show up on the bottom of the Visi-Pitch as a flat blue line. I will give you an example (give full model and point out the breaths between each step as shown on the Visi-Pitch). Keep Stepping up the scale until you feel like you can't make a higher sound. When you feel like you're reaching the top of your range try to hold the notes for 2 seconds. Watch the screen to see how high you are getting and how long you are holding the sound. Remember to take your deepest breath, start at a comfortable pitch, and go high as high as you can into falsetto. I want you to {ake a deep breath and p r o d u c e / d at a comfortable pitch and loudness level. Before moving down to the next note, I would like you to take a short breath in between. These short breaths between th e notes will show up on the bottom of the Vis~-Pitch as a flat blue line. I will give you an example (give futt model and point out the breaths between each step as shown on the Visi=Pitch). Keep stepping up the scale until you feel like you can't :
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make a lower sound. When you feel like you're reaching the bottom of your range try to hold the notes for 2 seconds. Watch the screen to see how low you are getting and how long you are holding the sound. Remember to take your deepest breath, start at a comfortable pitch, and go as low as you can into glottal fry.
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