Discrimination Functions: Can They Be Used to Classify Singing Voices?

Researchers long have searched for invariant acoustic features that can be used to identify singing voice categories or even individual singers. Few researchers have examined how listeners perceive singing voice categories or individual voices. Timbre, the most studied perceptual dimension of the singing voice, is generally believed to vary systematically between singing voice categories but is often assumed to be invariant with an individual singer. To test this assumption, 2 mezzo-sopranos and 2 sopranos were recorded singing the vowel /a/ on the pitches A3, C4, G4, B4, F5, and A5. Trials of three stimuli were constructed. Two of the three stimuli in each trial were produced by the same singer at two different pitches (X₁ and X₂), while the third stimulus was produced by a different singer (Y). Three X₁X₂ conditions were created: (1) G4, B4; (2) C4, F5; and (3) A3, A5. For each singer and each condition, Y was varied across the three remaining singers and across all six pitches. Experienced and inexperienced listeners were asked to identify which stimulus was produced by the “odd” person. The ability to correctly choose the odd person varied greatly depending on pitch factors, suggesting that the traditional concept of an invariant timbre associated with a singer is inaccurate and that vocal timbre must be conceptualized in terms of transformations in perceived quality that occur across an individual singer's range and/or registers.     

The relationship between measured vibrato characteristics and perception in Western operatic singing

This study examined the association between acoustic and perceptual data related to vibrato in Western operatic singing using recordings of performances by internationally famous opera singers. Three related studies were conducted. Study 1 used commercial recordings of the same five singers and the same cadenza examined by Siegwart and Scherer(1), measured vibrato rate and extent in each singer's performance of the cadenza and tested possible associations between these vibrato attributes and judges' preference for singers. Studies 2 and 3, using recordings of different internationally famous singers and a different cadenza, measured vibrato onset, rate, and extent in each singer's performance of the cadenza, required judges to rank the singers in order of personal preference, to identify the emotion expressed, and to assess the degree of success in communicating emotion achieved by the singer. The findings showed that the perception of the singers' vibrato did not always agree with acoustic measurements. However, a comparison of the acoustic measurements with the preference and emotion judgments suggest that some elements of vibrato may affect listeners' perception of the voice, their preference for a particular singer, and assist the communication of emotion between singer and audience.     

从表演者角度论述歌剧院的声学研究和设计

本文从解决歌手与乐队竞争的谜团入手,详述了歌剧院乐队演奏(缺乏高频声)和歌剧唱法(高频的歌手共振峰)的声音特点,进而提出了歌手和乐队之间平衡的声学设计(即放大歌手的歌唱声并适当降低乐队的演奏声,观众听起来歌手和乐队之间的声音保持平衡),重点论述了乐池的声学设计。然后分别从提高表演者的相互听闻(为了合奏的同步性)和提高房间的声反馈(为了控制演奏的响度)进行了论述,得出从表演者角度进行声学研究和设计的重要性。     

Pitch Discrimination and Pitch Matching Abilities of Adults who Sing Inaccurately

Past research regarding singing ability has provided evidence that both supports and refutes a relationship between pitch discrimination ability and pitch production ability. Researchers have suggested that these skills improve with age. Despite this suggestion, most investigators studying singing ability have included only children as participants. Additionally, although many researchers have studied accurate singers, few have directly studied persons who do not sing accurately. We designed this study to examine the relationship between pitch discrimination ability and pitch production ability in inaccurate adult singers. Fifteen adults, aged 18 to 40 years, that met specific criteria qualified as inaccurate singers. Each participated in two tasks, a pitch discrimination task and a pitch production task. We used the Multi-Dimensional Voice Profile-Advanced (Kay Elemetrics Corporation, Lincoln Park, NJ) to determine the frequency of each participant's vocal productions during the pitch production task. We also used a Pearson product moment correlation to analyze the relationship between pitch discrimination and pitch production accuracy within a semitone of the target frequency. No meaningful relationship was found, and results were not statistically significant. However, the inaccurate singers in this study could be classified into two separate categories, those who discriminated pitches accurately, but produced pitches inaccurately, and those who discriminated pitches inaccurately and produced pitches inaccurately. These findings may be of great importance to music educators and impact the focus of instruction when teaching an inaccurate singer to sing more accurately.     

Long-Term Horizontal Vocal Directivity of Opera Singers: Effects of Singing Projection and Acoustic Environment

Vocal directivity refers to how directional the sound is that comes from a singer's mouth, that is, whether the sound is focused into a narrow stream of sound projecting in front of the singers or whether it is spread out all around the singer. This study investigates the long-term vocal directivity and acoustic power of professional opera singers and how these vary among subjects, among singing projections, and among vastly different acoustic environments. The vocal sound of eight professional opera singers (six females and two males) was measured in anechoic and reverberant rooms and in a recital hall. Subjects sang in four different ways: (1) paying great attention to intonation; (2) singing as in performance, with all the emotional connection intended by the composer; (3) imagining a large auditorium; and (4) imagining a small theatre. The same song was sung by all singers in all conditions. A head and torso simulator (HATS), radiating sound from its mouth, was used for comparison in all situations. Results show that individual singers have quite consistent long-term average directivity, even across conditions. Directivity varies substantially among singers. Singers are more directional than the standard HATS (which is a physical model of a talking person). The singer's formant region of the spectrum exhibits greater directivity than the lower-frequency range, and results indicate that singers control directivity (at least, incidentally) for different singing conditions as they adjust the spectral emphasis of their voices through their formants.     

Long-Term-Average Spectrum Characteristics of Country Singers During Speaking and Singing

Five premier male country singers involved in our previous studies spoke and sang the words of both the national anthem and a country song of their choice. Long-term-average spectra were made of the spoken and sung material of each singer. The spectral characteristics of county singers' speech and singing were similar. A prominent peak in the upper part of the spectrum, previously described as the "speaker's formant," was found in the county singers' speech and singing. The singer's formant, a strong spectral peak near 2.8 kHz, an important part of the spectrum of classically trained singers, was not found in the spectra of the country singers. The results support the conclusion that the resonance characteristics in speech and singing are similar in country singing and that county singing is not characterized by a singer's formant.     

Voice Characteristics of Young Girl Role in Kunqu Opera

Three electroglottographic parameters, fundamental frequency, contact quotient, and speed quotient were analyzed for two singers of Young girl role in Kunqu Opera. Each singer performed three conditions, singing, stage speech, and reading lyrics. The phonation types adopted in different conditions were explored based on electroglottographic parameters. Fundamental frequency, contact quotient, and speed quotient showed different distributions among conditions. Five phonation types were used in singing and stage speech, which include (1) breathy voice, (2) modal voice with low degree of posterior glottal adduction, (3) modal voice, (4) falsetto, and (5) falsetto with high degree of posterior glottal adduction. The phonation strategies partly showed differences between singers. Different phonation type collocations were employed in singing and stage speech. The relationship between phonation types and pitch was complex. The phonation types actually used were different from and more complex than those in traditional Kunqu Opera singing theory.     

Effect of Hydration and Vocal Rest on the Vocal Fatigue in Amateur Karaoke Singers

Karaoke singing is a very popular entertainment among young people in Asia. It is a leisure singing activity with the singer's voice amplified with special acoustic effects in the backdrop of music. Music video and song captions are shown on television screen to remind the singers during singing. It is not uncommon to find participants singing continuously for four to five hours each time. As most of the karaoke singers have no formal training in singing, these amateur singers are more vulnerable to developing voice problems under these intensive singing activities. This study reports the performance of 20 young amateur singers (10 males and 10 females, aged between 20-25 years) on a series of phonatory function tasks carried out during continuous karaoke singing. Half of the singers were given water to drink and short duration of vocal rests at regular intervals during singing and the other half sang continuously without taking any water or rest. The subjects who were given hydration and vocal rests sang significantly longer than those who did not take any water or rest. The voice quality, as measured by perceptual and acoustic measures, and vocal function, as measured by phonetogram, did not show any significant changes during singing in the subjects who were given water and rest during the singing. However, subjects who sang continuously without drinking water and taking rests showed significant changes in the jitter measure and the highest pitch they could produce during singing. These results suggest that hydration and vocal rests are useful strategies to preserve voice function and quality during karaoke singing. This information is useful educational information for karaoke singers.     

Preferred self-to-other ratios in choir singing.

Choir singers need to hear their own voice in an adequate self-to-other ratio (SOR) over the rest of the choir. Knowing singers' preferences for SOR could facilitate the design of stages and of choral formations. In an experiment to study the preferred SOR, subjects sang sustained vowels together with synthesized choir sounds, whose loudness tracked that of their own voice. They could control the SOR simply by changing their distance to the microphone. At the most comfortable location, the SOR was measured. Experimental factors included unison and four-part tasks, three vowels and two levels of phonation frequency. The same experiment was run four times, using sopranos, altos, tenors, and basses, with stimulus tones adapted for each category. The preferred self-to-other ratios were found to be similar to SORs measured previously in actual performance, if a little higher. Preferences were quite narrow, typically +/- 2 dB for each singer, but very different from singer to singer, with intrasubject means ranging from -1 to +15 dB. There was no significant difference between the unison and the four-part tasks, although this might have been caused by systematic differences in the stimulus sounds. Some effects of phonation frequency and vowel were significant, but interdependent and difficult to interpret. The results and their relevance to live choir singing are discussed.     

Movement of the velum during speech and singing in classically trained singers

The present study addresses two questions: (a) Is the action and/orposture of the velopharyngeal valve conducive to allow significant resonance during Western tradition classical singing? (b) How do the actions of the velo-pharyngeal valve observed in this style of singing compare with normal speech? A photodetector system was used to observe the area function of the velopharyngeal port during speech and classical style singing. Identical speech samples were produced by each subject in a normal speaking voice and then in the low, medium, and high singing ranges. Results indicate that in these four singers the velopharyngeal port was closed significantly longer in singing than in speaking samples. The amount of time the velopharyngeal port was opened was greatest in speech and diminished as the singer ascended in pitch. In the high voice condition, little or no opening of the velopharyngeal port was measured.     

Physiological differences between the trained and untrained speaking and singing voice

This study concerns the premier singing voice and its relationship to physiological aptitude. Research literature is reviewed that indicates that during singing the trained singer uses different physiological strategies in comparison with the untrained singer, and that the noted physiological differences (respiratory, laryngeal, articulatory) occur during singing only and not during speech. Further, a study was conducted that compared the ability of trained singers versus untrained individuals to (a) discriminate differences in self-generated air pressures and (b) produce and maintain a constant level of air pressure. No significant differences were found between the trained and untrained groups in their ability to discriminate and/or control breath pressure. Combined results of previous studies and present findings lead to the tentative conclusion that the excelled singer is not physiologically endowed and/or “gifted,” but rather has benefited from technical voice training     

Vocal fold microsurgery in singers

Some singers with benign vocal fold mucosal lesions remain unacceptably impaired vocally in spite of compliance with a regimen of medical treatment and voice therapy lasting several months—or even years. I present here my experience with 62 singers who, because of this predicament, chose to undergo vocal fold microsurgery. This series is the second largest reported to date in English literature. Procedures are presented which were used for patient selection, education, and vocal retraining, as well as for surgery itself and postoperative care. Results reported here include (a) comparison of my auditory-perceptual ratings of singing voice impairment before and after surgery, (b) preoperative versus postoperative videostroboscopic findings, (c) postoperative rate of return to public singing, and (d) postoperative patient questionnaires which sought to uncover patient/singer perceptions of the results of vocal fold surgery. Excellent results were achieved overall with a very low incidence of untoward results, and no complications were encountered.     

The control of air flow during loud soprano singing

Previous research on the special characteristics of the professional singing voice has at least partially explained how singers can commonly use much higher lung pressures than nonsingers without vocal damage or excessive air flow during the voiced sounds. In this study, the control of air flow during the unvoiced consonants is examined for an operatic-style soprano. It was found that this singer could maintain a low average air flow during the consonants even though the lung pressure reached values over five times those used during normal conversational speech. The air flow was kept low primarily by the use of a number of mechanisms involving rapid, accurate, coordinated valving of the air flow at the point of articulation and at the glottis.     

Hearing myself with others: Sound levels in choral performance measured with separation of one's own voice from the rest of the choir

The choir singer has two acoustic signals to attend to: the sound of his or her own voice (feedback), and the sound of the rest of the choir (reference). The balance in loudness between feedback and reference is governed mainly by the room acoustics. Although earlier experiments have shown that singers have a fairly large tolerance for imbalance, with references ranging from −23 to +5 dB, experience suggests that, when singers are given control over this parameter, their preferences are much narrower. A quantification of the optimum balance would be useful in the design of concert stages and rehearsal halls. A method is described for measuring the feedback and reference levels as experienced by singers under live performance conditions. Recordings were made using binaural microphones worn by choir singer subjects. With the given combination of choir and room, it was possible to achieve adequate separation of the feedback and reference signals with simple signal processing. The feedback-to-reference ratio averaged over the 12 singers was found to be +3.9 dB, with extremes of +1.5 and +7.3 dB.     

Imprecise singing is widespread

There has been a recent surge of research on the topic of poor-pitch singing. However, this research has not addressed an important distinction in measurement: that between accuracy and precision. With respect to singing, accuracy refers to the average difference between sung and target pitches. Precision, by contrast, refers to the consistency of repeated attempts to produce a pitch. A group of 45 non-musician participants was asked to vocally imitate unfamiliar 5-note melodies, as well as to sing a series of familiar melodies from memory (e.g., Happy Birthday). The results showed that singers were more accurate than they were precise, and that a majority of participants could justifiably be categorized as imprecise singers. Accuracy and precision measures were correlated with one another, and conditional-probability analyses suggested that accuracy predicted precision more so than the converse. Finally, performance differences across groups of singers were greater for the imitation of unfamiliar tone sequences than for the recall of familiar melodies.     

Effects of a professional solo singer education on auditory and kinesthetic feedback—a longitudinal study of singers'' pitch control

The significance of auditory and kinesthetic feedback to pitch control in singing was described in a previous report of this project for students at the beginning of their professional solo singer education.(1) As it seems reasonable to assume that pitch control can be improved by training, the same students were reinvestigated after 3 years of professional singing education. As in the previous study, the singers sang an ascending and descending triad pattern with and without masking noise in legato and staccato and in a slow and a fast tempo. Fundamental frequency and interval sizes between adjacent tones were determined and compared with their equivalents in the equally tempered tuning. The average deviations from these values were used as estimates of intonation accuracy. Intonation accuracy was reduced by masking noise, by staccato as opposed to legato singing, and by fast as opposed to slow performance. The contribution of the auditory feedback to pitch control was not significantly improved after education, whereas the kinesthetic feedback circuit was improved in slow legato and slow staccato tasks. The results support the assumption that the kinesthetic feedback contributes substantially to intonation accuracy.     

Acoustical Comparison Between Samples of Good and Poor Vibrato in Singers

The purpose of this research was to analyze samples of frequency vibrato taken from recordings of eight different singers, which were classified as examples of good or poor singing. The samples were analyzed by a software package, which makes use of the linear prediction coding (LPC) method to determine the time varying rate and extent of the frequency vibrato wave. Four parameters, which relate to the periodicity of the samples, were extracted from the time varying rate and extent and investigated in order to verify or reject the hypothesis that the best vibrato samples were the most symmetric ones. Ten samples per singer were analyzed, 5 good and 5 poor, for a total of 80 samples. The results show that the samples judged as good were the most periodic ones.     

Singing proficiency in the general population

Most believe that the ability to carry a tune is unevenly distributed in the general population. To test this claim, we asked occasional singers (n=62) to sing a well-known song in both the laboratory and in a natural setting (experiment 1). Sung performances were judged by peers for proficiency, analyzed for pitch and time accuracy with an acoustic-based method, and compared to professional singing. The peer ratings for the proficiency of occasional singers were normally distributed. Only a minority of the occasional singers made numerous pitch errors. The variance in singing proficiency was largely due to tempo differences. Occasional singers tended to sing at a faster tempo and with more pitch and time errors relative to professional singers. In experiment 2 15 nonmusicians from experiment 1 sang the same song at a slow tempo. In this condition, most of the occasional singers sang as accurately as the professional singers. Thus, singing appears to be a universal human trait. However, two of the occasional singers maintained a high rate of pitch errors at the slower tempo. This poor performance was not due to impaired pitch perception, thus suggesting the existence of a purely vocal form of tone deafness.     

Comparing historical and contemporary opera singers with historical and contemporary Jewish cantors

This study is an attempt to ascertain if singers from different traditions and milieus follow similar aesthetic trends regardless of training and/or background. Cantors who sang the Jewish synagogue liturgy during the Golden Age of cantorial singing prior to World War II came from Eastern and Central Europe. For the most part, they were not trained in the classical Western opera tradition. They received training from choir leaders and other cantors and the training was primarily in the modes of synagogue chant. Cantors today receive the same kinds of training that opera singers receive, often from the same teachers. Four groups of singers, consisting of four singers in each group, were utilized in this study. The four groups are: historical opera singers, contemporary opera singers, historical cantors, and contemporary cantors. The historical opera singer recordings date from as early as 1909 to as late as 1939. It was not possible to determine the dates of the historical cantor recordings. However, the four cantors chosen for this group were active only to the 1940s. Contemporary samples were taken from CDs and/or live recordings and all the singers from the contemporary groups are either still active or were active in the 1960s through the 1980s and all of them are considered to be premier-level singers in their respective areas. The variables analyzed were: vibrato pulse rate, frequency variation of the vibrato pulse above and below the mean sustained sung frequency in percent, the mean amplitude variation of the amplitude vibrato pulse above and below the mean sustained amplitude in percent and the fast Fourier transform (FFT) power spectrum of the sustained samples. Results indicate that most of the significant differences were found between eras and not between groups within a time period.     

A Preliminary Study of Vocal Health Among Collegiate A Cappella Singers

ObjectiveCollegiate a cappella groups have grown significantly in popularity and prominence; however, there have been few studies that evaluate the vocal health of this subgroup of young singers. The objective of this preliminary study was to conduct a multiparametric evaluation of the vocal health characteristics of a sample of collegiate a cappella singers. We further tested whether differences in vocal health assessments exist between a cappella singers with and without vocal training and trained collegiate singers who do not participate in a cappella groups.Study designPoint prevalence study.MethodsForty-one collegiate singers participated in this study. Participants were divided into the following three groups: trained singers (TS), trained a cappella singers (ATS), and untrained a cappella singers (AUS). Participants were administered a set of surveys to assess self-perception of singing voice health and perceived access and attitudes toward voice-related health care. Acoustic and laryngoscopic assessments of participant's speaking and singing voice was performed and validated vocal health questionnaires administered as a means to objectively evaluate for the presence of voice problems.ResultsOverall, 87.5% of the ATS and 60% of the AUS groups reported experiencing problems with their singing voice. However, no vocal abnormalities were detected during laryngoscopic and acoustic assessments. Furthermore, minimal differences between any of the measured vocal health parameters were observed between the TS, ATS, and AUS groups.ConclusionCollectively, a high percentage of collegiate a cappella singers with and without vocal training report singing voice problems. However, our sample of a cappella singers did not have increased singing voice problems as compared to vocally trained collegiate singers not in a cappella groups. We did find that a cappella singers may be more inclined to seek information about maintaining a healthy singing voice from their fellow musicians as opposed to singing teachers or other voice health professionals. Singing teachers, otolaryngologists, and speech-language pathologists may need to play a more active role in educating a cappella singers regarding maintaining good vocal health.