Objective Analysis of Vocal Warm-Up with Special Reference to Ergonomic Factors

Vocal warm-up was studied in terms of changes in voice parameters during a 45-minute vocal loading session in the morning. The voices of a randomly chosen group of 40 female and 40 male young students were loaded by having them read a novel aloud. The exposure groups (5 females and 5 males per cell) consisted of eight combinations of the following factors: (1) low (25 +/- 5%) or high (65 +/- 5%) relative humidity of ambient air; (2) low [< 65 dB(SPL)] or high [> 65 dB(SPL)] speech output level during vocal loading; (3) sitting or standing posture during vocal loading. Two sets of voice samples were recorded: a resting sample before the loading session and a loading sample after the loading session. The material recorded consisted of /pa:ppa/ words produced normally, as softly and as loudly as possible in this order by all subjects. The long /a/ vowel of the test word was inverse-filtered to obtain the glottal flow waveform. Time domain parameters of the glottal flow [open quotient (OQ), closing quotient (CQ), speed quotient (SQ), fundamental frequency (F0)], amplitude domain parameters of the glottal flow [glottal flow (fAC) and its logarithm, minimum of the first derivative of the glottal flow (dpeak) and its logarithm, amplitude quotient (AQ), and a new parameter, CQAQ], intraoral pressure (p), and sound pressure level (SPL) values of the phonations were analyzed. Voice range profiles (VRP) and the singer's formant (g/G, a/A, cl/c, e1/e, g1/g for females/males) of the loud phonation were also measured. Statistically significant differences between the preloading and postloading samples could be seen in many parameters, but the differences depended on gender and the type of phonation. In females the values of CQ, AQ, and CQAQ decreased and the values of SQ and p increased in normal phonations; the values of fAC, dpeak, and SPL increased in soft phonations; the values of AQ and CQAQ decreased in loud phonations; the harmonic energy in the singer's formant region increased significantly at every pitch. In males the values of OQ and AQ decreased and the values of dpeak, F0, p, and SPL increased in normal phonations; the values of fAC and p increased in soft phonations. The changes could be interpreted as signs of a shift toward hyperfunctional voice production. Low humidity was associated with more hyperfunctional changes than high humidity. High output was associated with more hyperfunctional changes than low output. Sitting position was associated with an increasing trend at both margins of male VRP, whereas the case was the opposite for standing position.     

Glottal airflow and transglottal air pressure measurements for male and female speakers in soft, normal, and loud voice

Measurements on the inverse filtered airflow waveform (the "glottal waveform") and of estimated average transglottal pressure and glottal airflow were made from noninvasive recordings of productions of syllable sequences in soft, normal, and loud voice for 25 male and 20 female speakers. Statistical analyses showed that with change from normal to loud voice, both males and females produced loud voice with increased pressure, accompanied by increased ac flow and increased maximum airflow declination rate. With change from normal voice, soft voice was produced with decreased pressure, ac flow and maximum airflow declination rate, and increased dc and average flow. Within the loudness conditions, there was no significant male-female difference in air pressure. Several glottal waveform parameters separated males and females in normal and loud voice. The data indicate higher ac flow and higher maximum airflow declination rate for males. In soft voice, the male and female glottal waveforms were more alike, and there was no significant difference in maximum airflow declination rate. The dc flow did not differ significantly between males and females. Possible relevance to biomechanical differences and differences in voice source characteristics between males and females and across loudness conditions is discussed.     

Changes in glottal configuration in women after loud talking

The purpose of this investigation was to examine changes in glottal configuration in women under a variety of pitch and loudness conditions after an interval of loud reading. Twelve young adult women with normal laryngeal structures were photographed under stroboscopic light and sustained the vowel /i/ for a minimum of 3 s, at three pitch levels and three loudness levels, before and after a 15-min interval of loud reading. Results indicate that female speakers tend to alter glottic configurations across phonatory conditions after loud reading, particularly during high-pitch phonation. Specifically, five subjects tended to increase glottal closure, one tended to increase glottal opening, two tended to maintain the identical configuration, and four demonstrated no consistent pattern of response.     

Influence of glottal closure configuration on vocal efficacy in young normal-speaking women

Posterior closure insufficiency of the glottis is often mentioned in connection with permanent voice disorders. Recently published studies have revealed that an incomplete closure of the glottis can be found also in normal-speaking voices, especially in women. However, the effect of glottal closure configuration on vocal efficacy is not sufficiently clarified. The purpose of this study was to determine the effect of glottal closure configuration on singing and speaking voice characteristics. Overall, 520 young female normal-speaking subjects were examined by videostroboscopy for different phonation conditions in the combination of soft, loud, low, and/or high phonation and by voice range profile measurements. According to the videostroboscopic analysis, the subjects were subdivided into four groups: complete closure of the vocal folds already in soft phonation (group 1), closure of the vocal fold with increasing intensity (group 2), persistent closure insufficiencies despite increasing intensity (group 3), and hourglass-shaped closure in subjects with vocal nodules (group 4). Subjects in which the glottal closure could not be evaluated sufficiently were subclassified into group 5 (missing values).

Selected criteria of the singing and speaking voice were evaluated and statistically processed according to the mentioned subclassification. Group 1 reached significantly the highest sound pressure levels (SPL_max) for the singing voice as well as for the shouting voice. Group 3 showed a limited capacity to increase the intensity of the singing and speaking voice. The results gathered in this study objectify the relationship of insufficient glottal closure and reduced vocal capabilities. As long as no conclusive data on long-term consequences of insufficient glottal closure are available, a prophylactic improvement of the laryngeal situation especially in female professional voice users by voice therapy should be recommended.     

Estimating perceived phonatory pressedness in singing from flow glottograms

The normalized amplitude quotient (NAQ), defined as the ratio between the peak-to-peak amplitude of the flow pulse and the negative peak amplitude of the differentiated flow glottogram and normalized with respect to period time, has been shown to be related to glottal adduction. Glottal adduction, in turn, affects mode of phonation and hence perceived phonatory pressedness. The relationship between NAQ and perceived phonatory pressedness was analyzed in a material collected from a professional female singer and singing teacher who sang a triad pattern in breathy, flow, neutral, and pressed phonation in three different loudness conditions (soft, middle, loud). In addition, she also sang the same triad pattern in four different styles of singing, classical, pop, jazz, and blues, in the same three loudness conditions. A panel of experts rated the degree of perceived phonatory press along visual analogue scales. Comparing the obtained mean rated pressedness ratings with the mean NAQ values for the various triads showed that about 73% of the variation in perceived pressedness could be accounted for by variations of NAQ.     

Relationship between aerodynamic measures of glottal efficiency and stroboscopic findings in asymptomatic singing students

Singing requires exquisite coordination between the respiratory and phonatory systems to efficiently control glottal airflow. Asymptomatic singing students underwent pulmonary function testing (PFT), videostrobolaryngoscopic examination, and measures of glottal efficiency (maximum phonation time [MPT], glottal flow rate [GFR], and phonation quotient [PQ]) performed in both a sung and spoken tone. Pulmonary function and glottal efficiency values were within reported normative data for professional singers. However, sung tones were made with significantly higher GFR and PQ and lower PQ than spoken tones. The mean GFR was not related to the degree of glottal closure (by videostrobolaryngoscopy) or underlying pulmonary support.     

Effects of prolonged oral reading on F0, SPL, subglottal pressure and amplitude characteristics of glottal flow waveforms

The effects of prolonged (5x45 minute) reading (vocal loading) on fundamental frequency (F0), sound pressure level (SPL), subglottal (intraroral) pressure (p), and two glottal flow waveform parameters (AC amplitude of glottal flow, f, and negative peak amplitude of differentiated flow (d) of normal female and male subjects (N = 80) were studied. Two rest (morning and noon) and three loading (two in the morning and one in the afternoon) samples were recorded and analyzed. The glottal waveforms were obtained by inverse filtering of the acoustic pressure waveforms of speaking voice samples. The analyses were based on measurement and inverse filtering of the first stressed syllable of "paappa" words repeated 3x5 times for normal, as soft as possible, and as loud as possible phonation. In normal phonation the parameter values changed statistically significantly due to loading. In many cases the values obtained in the morning samples changed after the first loading session. This is interpreted as a vocal "warming-up effect." Especially in soft phonation p, d, and f were sensitive indicators of vocal loading. In both normal and soft phonation, the SPL, p, d, and f values tended to rise due to prolonged reading in the morning and afternoon samples, indicating increased effort (normal phonation) and a rise in the phonatory threshold (soft phonation). The lunch break vocal rest ("rest effect") considerably affected the parameter values in many cases.     

Glottal configuration associated withfundamental frequency and vocal register

Simultaneous measurements of mean airflow rate, vocal intensityand fundamental frequency were made during flexible video endoscopic recording of the vowel /i/ sustained in two vocal registers, modal and falsetto. The glottal closure patterns of four males and four females were evaluated by visually inspecting the video images. Acoustic signals were recorded and analyzed to verify the frequency and intensity criteria. Aerodynamic analysis of mean airflow rate was done via Rothenberg mask and commercial software. Incomplete glottic closure was common in both males and females. The degree of closure was significantly higher for modal samples than for falsetto samples with frequency and intensity held constant. The shape of the glottal closure did not vary with changes in the mode of phonation. As expected, the mean airflow rate increased with decreased glottal closure. The results suggest that incomplete glottic closure should be considered as a normal glottal configuration in high frequency modal and falsetto phonation. Moreover, hourglass and spindle glottal configurations may also be found in both the modal and falsetto registers of normal subjects. These results also confirm the positive relationships between degree of glottal gap and mean airflow rate. Thus, mean airflow rate may be regarded as a criterion for judging degree of glottal closure.     

Phonatory control in male singing: A study of the effects of subglottal pressure, fundamental frequency, and mode of phonation on the voice source

This article describes experiments carried out in order to gain a deeper understanding of the mechanisms underlying variation of vocal loudness in singers. Ten singers, two of whom are famous professional opera tenor soloists, phonated at different pitches and different loudnesses. Their voice source characteristics were analyzed by inverse filtering the oral airflow signal. It was found that the main physiological variable underlying loudness variation is subglottal pressure (Ps). The voice source property determining most of the loudness variation is the amplitude of the negative peak of the differentiated flow signal, as predicted by previous research. Increases in this amplitude are achieved by (a) increasing the pulse amplitude of the flow waveform; (b) moving the moment of vocal fold contact earlier in time, closer to the center of the pulse; and (c) skewing the pulses. The last mentioned alternative seems dependent on both Ps and the ratio between the fundamental frequency and the first formant. On the average, the singers doubled Ps when they increased fundamental frequency by one octave, and a doubling of the excess Ps over threshold caused the sound pressure level (SPL) to increase by 8–9 dB for neutral phonation, less if mode of phonation was changed to pressed. A shift of mode of phonation from flow over neutral to pressed was associated with a reduction of the peak glottal permittance i.e., the ratio between peak transglottal airflow to Ps. Flow phonation had the most favorable relationship between Ps and SPL.     

Optimal glottal configuration for ease of phonation

Recent experimental studies have shown the existence of optimalvalues of the glottal width and convergence angle, at which the phonation threshold pressure is minimum. These results indicate the existence of an optimal glottal configuration for ease of phonation, not predicted by the previous theory. In this paper, the origin of the optimal configuration is investigated using a low dimensional mathematical model of the vocal fold. Two phenomena of glottal aerodynamics are examined: pressure losses due to air viscosity, and air flow separation from a divergent glottis. The optimal glottal configuration seems to be a consequence of the combined effect of both factors. The results agree with the experimental data, showing that the phonation threshold pressure is minimum when the vocal folds are slightly separated in a near rectangular glottis.