Can Inexperienced Listeners Hear Who Is Singing? The Role of Motivation in Singer Discrimination Across Pitch.

OBJECTIVE: Previous research has shown that in a task identifying singers across pitch, inexperienced listeners perform very poorly compared to their experienced counterparts. This poor performance may partially be due to lower motivation and reduced attention on the part of inexperienced listeners. The current experiment is designed to examine the role of motivation in difficult perceptual tasks through use of an established methodology that uses singing voice stimuli. METHODS: This study used an ABX paradigm. Listeners heard two different singers, singing /ɑ/ at the same pitch and had to identify which of the two singers produced a third /ɑ/ at a different pitch. Pitches varied across 1.5 octaves. Inexperienced listeners were randomly assigned to 1 of 3 conditions: (1) no feedback, (2) percent correct feedback, and (3) percentile feedback. Prior to the experiment, listeners rated their motivation using the Situational Intrinsic Motivation Scale (SIMS). Data were collected from 99 inexperienced listeners. RESULTS: There were no significant differences between the three feedback conditions, No Feedback, Percent Correct, and Percentile, for any SIMS subscale. Likewise, there were no significant differences in musical experience between the three feedback conditions. A repeated measures ANOVA designed to test the effect of feedback group on mean percent correct responses revealed no significant main or interaction effects of feedback. However, amotivation was a significant predictor of mean percent correct scores. CONCLUSIONS: Motivation is a complex construct that, while not being a primary factor in the current audio-perceptual task, could still be an important confounding factor in perceptual research. In the case of the current study, the two feedback conditions utilized in this study, Percent Correct and Percentile, may not have provided sufficiently robust external motivation to elicit differences in performance. Perceptual and behavioral researchers should be vigilant. More research is necessary.

Experienced and Inexperienced Listeners' Perception of Vocal Strain.

OBJECTIVE: The ability to perceive strain or tension in a voice is critical for both speech-language pathologists and singing teachers. Research on voice quality has focused primarily on the perception of breathiness or roughness. The perception of vocal strain has not been extensively researched and is poorly understood. METHODS/DESIGN: This study employs a group and a within-subject design. Synthetic female sung stimuli were created that varied in source slope and vocal tract transfer function. Two groups of listeners, inexperienced listeners and experienced vocal pedagogues, listened to the stimuli and rated the perceived strain using a visual analog scale Synthetic female stimuli were constructed on the vowel /ɑ/ at 2 pitches, A3 and F5, using glottal source slopes that drop in amplitude at constant rates varying from - 6 dB/octave to - 18 dB/octave. All stimuli were filtered using three vocal tract transfer functions, one derived from a lyric/coloratura soprano, one derived from a mezzo-soprano, and a third that has resonance frequencies mid-way between the two. Listeners heard the stimuli over headphones and rated them on a scale from "no strain" to "very strained" using a visual-analog scale. RESULTS: Spectral source slope was strongly related to the perception of strain in both groups of listeners. Experienced listeners' perception of strain was also related to formant pattern, while inexperienced listeners' perception of strain was also related to pitch. CONCLUSION: This study has shown that spectral source slope can be a powerful cue to the perception of strain. However, inexperienced and experienced listeners also differ from each other in how strain is perceived across speaking and singing pitches. These differences may be based on both experience and the goals of the listener.

Experienced Listeners' Perception of Timbre Dissimilarity Within and Between Voice Categories.

OBJECTIVE/HYPOTHESES: The terms "soprano" and "mezzo-soprano" are frequently used by vocal pedagogues to describe a main category of singing timbre categorization, while the terms "lyric" and "dramatic" are often used to describe sub-categories of "soprano" and "mezzo-soprano". A handful of studies have reported on the perceptual dissimilarity of main voice categories, but few, if any, have focused on within voice category perceptual distinctions such as dramatic and lyric vocal timbre. Using stimuli collected from cisgender female singers of varying voice categories and voice weights across the pitches C4, G4, and F5, this study sought (1) to visualize an experienced listener's perception of vocal timbre dissimilarity within and between voice categories using the statistical technique of multidimensional scaling (MDS), (2) to identify salient acoustic predictors of voice category and voice weight, and (3) to determine any dependencies on pitch for the perception of vocal timbre. METHOD/DESIGN: For the pitches C4, G4, and F5, experienced listeners (N=18) rated the dissimilarity of pairs of sung vowels produced by classically trained singers classified as follows: six mezzo-sopranos (three lighter and three heavier) and six sopranos (three lighter and three heavier). The resulting dissimilarity data were analyzed using MDS. Backward linear regression was used to see if one or more of the following variables predicted MDS dimensions: spectral centroid from 0 to 5 kHz, spectral centroid from 0 to 2 kHz, spectral centroid from 2 to 5 kHz, frequency vibrato rate, and frequency vibrato extent. Listeners also completed a categorization task where they rated each individual stimulus on two dimensions: voice category and voice weight. RESULTS: Visual analysis of the MDS solutions appears to show that both voice category and voice weight emerged as dimensions at pitches C4 and G4. Discriminant analysis, on the other hand, statistically confirmed both these dimensions at G4, but only voice weight at C4. At pitch F5, only voice weight emerged as a dimension, both visually and statistically. Acoustic predictors of MDS dimensions were highly variable across pitches. At the pitch C4, no MDS dimension was predicted by the acoustic variables. At pitch G4, the dimension associated with voice weight was predicted by spectral centroid from 0 to 2 kHz. At pitch F5, the dimension associated with voice weight was predicted by spectral centroid from 2 to 5 kHz and frequency vibrato rate. In the categorization task, voice category and voice weight were highly correlated at the pitches C4, G4, and when all pitches were presented together, but weakly correlated at the pitch F5. CONCLUSION: While voice category and sub-category distinctions are commonly used by singing voice professionals to describe the overall timbre of voices, these distinctions may not be able to consistently predict the perceptual difference between any given pair of vocal stimuli, particularly across pitch. Nonetheless, these dimensions do emerge in some fashion when listeners are presented with paired vocal stimuli. On the other hand, when asked to rate stimuli according to the specific labels of mezzo-soprano/soprano and dramatic/lyric, experienced listeners have a very difficult time disentangling voice category from voice weight when presented with a single-note stimulus or even a 3-note stimulus consisting of the pitches C3, G4, and F5.

Multidimensional Timbre Spaces of Cochlear Implant Vocoded and Non-vocoded Synthetic Female Singing Voices.

Many post-lingually deafened cochlear implant (CI) users report that they no longer enjoy listening to music, which could possibly contribute to a perceived reduction in quality of life. One aspect of music perception, vocal timbre perception, may be difficult for CI users because they may not be able to use the same timbral cues available to normal hearing listeners. Vocal tract resonance frequencies have been shown to provide perceptual cues to voice categories such as baritone, tenor, mezzo-soprano, and soprano, while changes in glottal source spectral slope are believed to be related to perception of vocal quality dimensions such as fluty vs. brassy. As a first step toward understanding vocal timbre perception in CI users, we employed an 8-channel noise-band vocoder to test how vocoding can alter the timbral perception of female synthetic sung vowels across pitches. Non-vocoded and vocoded stimuli were synthesized with vibrato using 3 excitation source spectral slopes and 3 vocal tract transfer functions (mezzo-soprano, intermediate, soprano) at the pitches C4, B4, and F5. Six multi-dimensional scaling experiments were conducted: C4 not vocoded, C4 vocoded, B4 not vocoded, B4 vocoded, F5 not vocoded, and F5 vocoded. At the pitch C4, for both non-vocoded and vocoded conditions, dimension 1 grouped stimuli according to voice category and was most strongly predicted by spectral centroid from 0 to 2 kHz. While dimension 2 grouped stimuli according to excitation source spectral slope, it was organized slightly differently and predicted by different acoustic parameters in the non-vocoded and vocoded conditions. For pitches B4 and F5 spectral centroid from 0 to 2 kHz most strongly predicted dimension 1. However, while dimension 1 separated all 3 voice categories in the vocoded condition, dimension 1 only separated the soprano stimuli from the intermediate and mezzo-soprano stimuli in the non-vocoded condition. While it is unclear how these results predict timbre perception in CI listeners, in general, these results suggest that perhaps some aspects of vocal timbre may remain.

Can Listeners Hear Who Is Singing? The Role of Listener Experience in Singer Discrimination Across Pitch.

OBJECTIVE/HYPOTHESIS: Previous research has shown that listeners are unable to identify who is singing across pitch when the voices are unfamiliar to them. Implementing a very short training period, however, greatly improves this ability, but only when the voices being compared are of different voice category. The objective of this study was to determine whether experienced listeners with highly developed knowledge of voice categories can more easily discriminate between singers across pitch. METHODS/DESIGN: This study used an ABX paradigm where listeners heard two different singers singing "ah" at the same pitch. Listeners identified which of the two singers produced a third "ah" at a different pitch. Stimuli were recorded from two baritones, two tenors, two mezzo-sopranos, and two sopranos across a 1.5 octave range. Data were collected from 42 inexperienced listeners and 27 experienced listeners. RESULTS: Experienced listeners were better at singer discrimination across pitch than were inexperienced listeners for all conditions except same-category comparisons at the interval of the third. Experienced listeners were better at singer discrimination across pitch than were slightly trained listeners for all conditions except same-category female singers at all pitch intervals. CONCLUSIONS: The ability to discriminate singers across pitch is the greatest for experienced listeners, followed by slightly trained inexperienced listeners, followed by inexperienced listeners.

Inexperienced Listeners' Perception of Timbre Dissimilarity Within and Between Voice Categories.

OBJECTIVE/HYPOTHESIS: Using stimuli produced by classically trained female singers, this study sought to examine how inexperienced listeners' ratings of timbre dissimilarity relate to singer categorization, both between and within voice category. METHOD/DESIGN: Stimuli were produced by six mezzo-sopranos and six sopranos classically trained female voice students at three pitches, C4, G4, and F5. Within each category, mezzo-soprano and soprano, three singers were classified as lighter in timbre and three were classified as heavier in timbre. At each pitch, the 12 sung stimuli were combined in all possible pairs and presented to 56 inexperienced listeners who judged each pair for the degree of timbre dissimilarity using a visual analog scale. All stimuli also were rated by expert voice professionals in two dimensions: (1) voice category and (2) vocal weight. RESULTS: Multidimensional scaling (MDS) dimensions agreed with teacher-determined voice category at C4 and teacher-determined vocal weight at G4 and F5. MDS dimensions also correlated with single-note ratings of voice category and vocal weight provided by expert listeners who were unfamiliar with the singing voices used in this study. With limited exceptions, no single acoustic variable predicted the MDS dimensions that resulted from the inexperienced listeners ratings of timbre dissimilarity; however, weighted linear combinations of acoustic variables were highly predictive of numerous MDS dimensions. CONCLUSION: In spite of a lack of both range and tessitura information, timbre dissimilarity ratings provided by inexperienced listeners yielded MDS dimensions that accurately predicted voice categories and vocal weight and that highly correlated to expert listeners ratings of these two parameters.

Can Inexperienced Listeners Hear Who Is Singing? The Role of Onset Cues.

OBJECTIVE/HYPOTHESIS: This study sought to determine whether the acoustic information contained in the onset of phonation can improve the ability to discriminate voices across pitch. STUDY DESIGN: This study was a repeated-measures factorial design. METHODS: Listeners heard two singers producing /ɑ/ at the same pitch and an unknown singer producing /ɑ/ at a different pitch. Listener's identified which singer was the unknown singer. Two baritones and two tenors were recorded producing /ɑ/ at the pitches C3, E3, G3, B3, D4, and F4. Two sopranos and two mezzo-sopranos were recorded producing /ɑ/ at the pitches C4, E4, G4, B4, D5, and F5. For each group of stimuli, male and female, all possible pairs of singers were constructed for the lowest pitch. The unknown singer was varied across the remaining pitches. All stimulus combinations were presented with and without onset cues. RESULTS: In general, the inclusion of onset information affected listeners' ability to discriminate singers across pitch. When the pitch interval was small, a 3rd or a 5th, onset information improved the ability to correctly discriminate singers across pitch. This effect was greater for female voices than for male voices. However, when the pitch interval was larger, a 7th, 9th, or 11th, the onset information either had no effect, as was seen in the female voices, or had a negative effect, as was seen in the male voices. CONCLUSION: Voice onset information affects voice discrimination in certain circumstances, but cannot be used by inexperienced listeners as a consistent cue to improve singer discrimination across all pitch intervals.

Can Listeners Hear Who Is Singing? The Development of Voice Category Perception.

OBJECTIVE AND HYPOTHESIS: This study sought to investigate if a small amount of training in identification of voices elicits the development of prototypical vocal categories. STUDY DESIGN: This study used a between-group design. METHODS: This study used an ABX paradigm where listeners heard two different singers singing "ah" at the same pitch. Listeners identified which of the two singers was the producer of a third "ah" at a different pitch. Stimuli were recorded from two baritones, two tenors, two mezzo-sopranos, and two sopranos across a 1.5-octave range. Participants were randomly assigned to two groups, one group that received a training session using voices that were different from those in the experimental session, but of the same voice category, and one group that received no training. RESULTS: Training listeners with voices that are different from those of singers presented in the experiment did not significantly improve the ability to discriminate individual voices of the same voice category, but did significantly improve that ability to discriminate individual voices when the voices being compared were of different voice categories. CONCLUSIONS: Small amounts of purposeful exposure to human voices appear to result in the beginnings of listener voice category formation, providing listeners with prototypical categories that can aid them in discrimination of novel voices of those same categories.

Acoustic Properties of the Voice Source and the Vocal Tract: Are They Perceptually Independent?

OBJECTIVE/HYPOTHESIS: This study sought to determine whether the properties of the voice source and vocal tract are perceptually independent. STUDY DESIGN: Within-subjects design. METHODS: This study employed a paired-comparison paradigm where listeners heard synthetic voices and rated them as same or different using a visual analog scale. Stimuli were synthesized using three different source slopes and two different formant patterns (mezzo-soprano and soprano) on the vowel /a/ at four pitches: A3, C4, B4, and F5. RESULTS: Whereas formant pattern was the strongest effect, difference in source slope also affected perceived quality difference. Source slope and formant pattern were not independently perceived. CONCLUSION: These results suggest that when judging laryngeal adduction using perceptual information, judgments may not be accurate when the stimuli are of differing formant patterns.

Can Inexperienced Listeners Hear Who Is Flat? The Role of Timbre and Vibrato.

OBJECTIVES/HYPOTHESIS: Research has shown that the distribution of spectral energy and the presence of vibrato in a complex tone can affect pitch perception. This study sought to answer the questions: "Does timbre affect the perception of difference in pitch in complex synthetic stimuli modeled after singing voices?" "Does vibrato affect the perception of difference in pitch in complex synthetic stimuli modeled after singing voices?" and "Does the direction of timbre difference affect the perception of pitch difference?" STUDY DESIGN: This is a repeated-measures factorial design. METHODS: The experiment consisted of three experimental blocks at the pitches A3, G4, and F5, each with a vibrato and no-vibrato subblock. For each block, two reference stimuli (mezzo-soprano and soprano) and six test stimuli (mezzo-soprano at frequencies of -1%, -2%, and -3%, soprano at frequencies of -1%, -2%, and -3%) were synthesized on the vowel /ɑ/. Each reference stimulus was paired with itself, with the other reference stimulus, and with all the test stimuli. Vibrato stimuli had a rate of 5.6 Hz and a frequency vibrato extent of ±50 cents. Listeners indicated the degree to which stimuli differed in pitch. RESULTS: Differences in timbre and vibrato were significant main effects on the perception of pitch difference. The direction of timbre difference was a consistent significant effect on the perception of pitch difference for the pitch G4; however, this was not a consistent effect at the pitches A3 and F5. CONCLUSION: Numerous factors can affect the perception of pitch including timbre and presence of vibrato.

Can Listeners Hear Who Is Singing? The Role of Familiarity.

OBJECTIVE/HYPOTHESIS: This study sought to determine whether familiarity with voices increases discrimination of voices across pitch intervals. STUDY DESIGN: This is a between-group design. METHODS: This study used a forced-choice paradigm where listeners heard two different singers (singer 1 and singer 2) producing /ɑ/ at the identical pitch and an unknown singer (either singer 1 or singer 2) producing /ɑ/ at a different pitch. Listeners had to identify which singer was the unknown singer. Two baritones and two tenors were recorded producing /ɑ/ at the pitches C3, E3, G3, B3, D4, and F4. Two sopranos and two mezzo-sopranos were recorded producing /ɑ/ at the pitches C4, E4, G4, B4, D5, and F5. For each group of stimuli, male and female, all possible pairs of singers were constructed for the lowest pitch (C2 or C3, respectively) and for the highest pitch (F4 or F5, respectively). The unknown singer was varied across the remaining pitches. Participants in group 1 completed a training session where they were familiarized with the voices being tested. Participants in group 2 did not. RESULTS: Training did not significantly improve the ability to discriminate voices when the voices being compared were of the same voice category. However, training did significantly improve the ability to discriminate voices when the voices being compared were of different voice categories even when training lasted as little as 5 minutes. CONCLUSIONS: Small amount of exposure to human voices results in voice category formation but does not result in the formation of models of individual voices.

Can listeners hear how many singers are singing? The effect of listener's experience, vibrato, onset, and formant frequency on the perception of number of simultaneous singers.

OBJECTIVE/HYPOTHESIS: This study investigated whether listener's experience, presence/absence of vibrato, formant frequency difference, or onset delay affect the ability of experienced and inexperienced listeners to segregate complex vocal stimuli. STUDY DESIGN: Repeated measures factorial design. METHODS: Two sets of stimuli were constructed: one with no vibrato and another with vibrato. For each set, each stimulus was synthesized at four pitches: A3, E4, B4, and F5. Stimuli were synthesized using formant patterns appropriate for the vowel |ɑ|. Frequencies for formants one through four were systematically varied from lower to higher in an attempt to simulate the acoustic results of corresponding changes in vocal tract length. Four formant patterns were synthesized (patterns A-D). Three pairs were created at each pitch, pairing the formants AB (mezzo-soprano/mezzo-soprano), CD (soprano/soprano), and AD (mezzo-soprano/soprano). Each of these three pairs was constructed in three separate conditions: simultaneous onset; the first voice in the pair with an onset delay of 100 milliseconds; and the second voice in the pair with an onset delay of 100 milliseconds. Using a scroll bar, listeners rated how difficult it was for them to hear each stimulus pair as two separate voices. RESULTS: The most difficult combinations to segregate were produced with no vibrato and used simultaneous onset. The easiest conditions to segregate were combinations including a "soprano-like" formant pattern (D) in the vibrato condition. Overall, listener's experience did not affect the perceived difficulty of segregation; however, in the presence of vibrato cues, inexperienced listeners did not use delay cues as an aid in segregation in the same manner as did experienced listeners. Once vibrato was removed from the experimental context, inexperienced listeners were able to use delay to aid in segregation in a similar manner to experienced listeners. CONCLUSION: Presence/absence of vibrato, formant pattern difference, and onset delay interact in a complex manner to affect the perceived difficulty of voice segregation.

The Traditional/Acoustic Music Project: a study of vocal demands and vocal health.

OBJECTIVE/HYPOTHESIS: The Traditional/Acoustic Music Project seeks to identify the musical and performance characteristics of traditional/acoustic musicians and determine the vocal demands they face with the goals of (1) providing information and outreach to this important group of singers and (2) providing information to physicians, speech-language pathologists, and singing teachers who will enable them to provide appropriate services. STUDY DESIGN: Descriptive cross-sectional study. METHODS: Data have been collected through administration of a 53-item questionnaire. The questionnaire was administered to artists performing at local venues in Knoxville, Tennessee and also to musicians attending the 2008 Folk Alliance Festival in Memphis, Tennessee. RESULTS: Approximately 41% of the respondents have had no vocal training, whereas approximately 34% of the respondents have had some form of formal vocal training (private lessons or group instruction). About 41% of the participants had experienced a tired voice, whereas about 30% of the participants had experienced either a loss of the top range of the voice or a total loss of voice at least once in their careers. Approximately 31% of the respondents had no health insurance. Approximately 69% of the respondents reported that they get their information about healthy singing practices solely from fellow musicians or that they do not get any information at all. CONCLUSION: Traditional/acoustic musicians are a poorly studied population at risk for the development of voice disorders. Continued research is necessary with the goal of a large sample that can be analyzed for associations, identification of subpopulations, and formulation of specific hypotheses that lend themselves to experimental research. Appropriate models of information and service delivery tailored for the singer-instrumentalist are needed.

Can listeners hear who is singing? What is the pitch bandwidth of singer discrimination in untrained listeners?

OBJECTIVE/HYPOTHESIS: This study sought to determine the pitch bandwidth of singer discrimination based on singer gender, pitch range, and same-different voice category. STUDY DESIGN: Repeated measures factorial design. METHODS: This study used a forced-choice paradigm, where listeners heard two different singers (singer 1 and singer 2) producing /ɑ/ at an identical pitch and an unknown singer (either singer 1 or singer 2) producing /ɑ/ at a different pitch. It was the listener's task to identify which singer (singer 1 or singer 2) was the unknown singer. Two baritones and two tenors were recorded producing /ɑ/ at the pitches C3, E3, G3, B3, D4, and F4. Two sopranos and two mezzo-sopranos were recorded producing /ɑ/ at the pitches C4, E4, G4, B4, D5, and F5. For each group of stimuli, male and female, all possible pairs of singers were constructed for the lowest pitch (C2 or C3, respectively) and highest pitch (F4 or F5, respectively). The unknown singer was varied across the remaining pitches. RESULTS: For between category comparisons, the ability to discriminate singers diminished monotonically with pitch interval, reaching below chance levels between the intervals of the 9th and 11th. For within category comparisons, it was much harder to discriminate singers across pitch, particularly when the voices were female. CONCLUSION: Timbre is not perceived as invariant across the entire singing range, and the bandwidth of this timbre invariance depends on multiple factors, including pitch range, gender, and same-different voice category.

The effect of an artificially lengthened vocal tract on estimated glottal contact quotient in untrained male voices.

The use of hard-walled narrow tubes, often called resonance tubes, for the purpose of voice therapy and voice training has a historical precedent and some theoretical support, but the mechanism of any potential benefit from the application of this technique is not well understood. Fifteen vocally untrained male participants produced a series of spoken /a/ vowels at a modal pitch and constant loudness, before and after a minute of repeated phonation into a 50-cm hard-walled glass tube at the same pitch and loudness targets. Electroglottography was used to measure the glottal contact quotient (CQ) during each phase of the experiment. Single-subject analysis revealed statistically significant changes in CQ during tube phonation, but with no discernable pattern across the 15 participants. These results indicate that the use of resonance tubes can have a distinct effect on glottal closure, but the mechanism behind this change remains unclear. The implication is that vocal loading techniques such as this need to be studied further with specific attention paid to the underlying mechanism of any measured changes in glottal behavior, and especially to the role of instruction and feedback in the therapeutic and pedagogical application of these techniques.

Can listeners hear who is singing? Part B--experienced listeners.

Previous research has shown that inexperienced listeners have a more difficult time identifying an oddball singer in a three-note task where two sung stimuli are produced by the same singer and one sung stimulus is produced by an oddball singer than they do in a six-note task where five sung stimuli are produced by the same singer and one sung stimulus is produced by the oddball singer. Such results support the idea that timbre should be understood as a transformation that connects the different sounds of one source, that a "rich" set of sounds is necessary to discover the trajectory. The role of listener experience in perceiving the trajectory, however, is unknown. This paper investigated the ability of experienced listeners to identify which pitch in an ascending or descending sequence of three or six stimuli was sung by a different singer. For three-note sequences, listeners for the most part chose the most dissimilarly pitched stimulus as coming from the oddball singer. For six-note sequences, the detection of the oddball singer was much improved. In all tasks, experienced listeners were better able to detect the oddball singer than were inexperienced listeners. These results support the idea that while listener experience is an important factor in singer discrimination, experienced and inexperienced listeners alike benefit from a "rich" set of exemplars from which to abstract the timbre transformation.

The effect of a voiced lip trill on estimated glottal closed quotient.

The use of lip trills has been advocated for both vocal habilitation and rehabilitation. A voiced lip trill requires continuous vibration of the lips while simultaneously maintaining phonation. The mechanism of any effects of a lip trill on vocal fold vibration is still unknown. While other techniques that either constrict or artificially lengthen the vocal tract have been investigated, no studies thus far have systematically examined the effect of lip trills on vocal fold vibration. Classically trained singers and vocally untrained participants produced a lip trill for approximately 1 minute, and vocal fold closed quotient (CQ) was calculated both during the lip trill and on a sustained spoken vowel before and after the trill. Data are reported for both a group design and a single-subject design. Most participants showed a tendency for a reduction in CQ during the lip trill, with a more pronounced change in the untrained participants.

Dissimilarity and the classification of male singing voices.

Traditionally, timbre has been defined as that perceptual attribute that differentiates two sounds when pitch and loudness are equal, and thus is a measure of dissimilarity. By such a definition, each voice possesses a set of timbres, and the ability to identify any voice or voice category across different pitch-loudness-vowel combinations must be due to an ability to "link" these timbres by abstracting the "timbre transformation," the manner in which timbre subtly changes across pitch and loudness for a specific voice or voice category. Using stimuli produced across the singing range by singers from different voice categories, this study sought to examine how timbre and pitch interact in the perception of dissimilarity in male singing voices. This study also investigated whether or not listener experience affects the perception of timbre as a function of pitch. The resulting multidimensional scaling (MDS) representations showed that for all stimuli and listeners, dimension 1 correlated with pitch, while dimension 2 correlated with spectral centroid and separated vocal stimuli into the categories baritone and tenor. Dimension 3 appeared highly idiosyncratic depending on the nature of the stimuli and on the experience of the listener. Inexperienced listeners appeared to rely more heavily on pitch in making dissimilarity judgments than did experienced listeners. The resulting MDS representations of dissimilarity across pitch provide a glimpse of the timbre transformation of voice categories across pitch.

The interaction of formant frequency and pitch in the perception of voice category and jaw opening in female singers.

This study represents a first step toward understanding the contribution formant frequency makes to the perception of female voice categories. The effects of formant frequency and pitch on the perception of voice category were examined by constructing a perceptual study that used two sets of synthetic stimuli at various pitches throughout the female singing range. The first set was designed to test the effects of systematically varying formants 1 through 4. The second set was designed to test the relative effects of lower frequency formants (F1 and F2) versus higher frequency formants (F3 and F4) through construction of mixed stimuli. Generally, as the frequencies of all four formants decreased, perception of soprano voice category decreased at all but the highest pitch, A5. However, perception of soprano voice category also increased as a function of pitch. Listeners appeared to need agreement between all four formants to perceive voice categories. When upper and lower formants are inconsistent in frequency, listeners were unable to judge voice category, but they could use the inconsistent patterns to form perceptions about degree of jaw opening.

Effects of voicing and syntactic complexity on sign expression in adductor spasmodic dysphonia.

Clients with adductor spasmodic dysphonia (ADSD) tend to exhibit inter- and intraclient variability of signs and symptoms. This variability may result in inaccurate assessment of severity. Accurate assessment of severity requires knowledge concerning the factors that affect the expression of ADSD signs and symptoms. This study examined ADSD sign expression as a function of voicing and syntactic complexity. Fifteen ADSD participants and 15 control participants completed a task consisting of 30 sentences. ADSD signs were significantly more frequent in predominantly voiced sentences than in predominantly voiceless sentences, regardless of level of syntactic complexity. Center-embedded sentences comprising predominantly voiced consonants were found to evoke the greatest number of ADSD signs. These results have important implications for the assessment of ADSD.