Vocal loading-related subjective symptoms were studied in a day-long vocal loading test. The voices of 40 female and 40 male voluntary young students were loaded by having them read aloud a novel for five times 45 min. The subjective symptoms that occurred during the vocal loading session were reported by filling in a questionnaire after each session. The responses loaded on five factors in a factor analysis: (1) ‘central fatigue’; (2) ‘symptoms of the neck, shoulders and back’; (3) ‘drying in the mouth and throat’; (4) ‘symptoms of the throat’; (5) ‘symptoms of the voice’. 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 of vocal loading; (3) sitting or standing posture during vocal loading. The lowest mean score for symptoms pooled over the test were found in ‘symptoms of the neck, shoulders and back’ and the highest mean symptom score in ‘drying in the mouth and throat’ and ‘symptoms of the throat’. Most symptoms were at their minimum during the first loading session and increased statistically significantly to a peak mean value after three or five vocal loading sessions. Statistically significant differences in the mean level between the gender or exposure groups emerged for ‘central fatigue’ (humidity had clear effects) and ‘symptoms of the neck, shoulders and back’ (gender, humidity and posture had clear effects). In these cases, females had more symptoms than males; the low-humidity group had more symptoms than the high-humidity group, and the standing subjects had more symptoms than the sitting subjects.
In all, 32 of 33 laryngeal fracture patients had blunt trauma and the main causative factors were sport injuries (39%) and physical assault (33%). All of the 33 laryngeal fracture patients had a good airway outcome. The subjective voice outcome was good for 20 (61%) and fair for 13 (39%) patients. The mean follow-up time was 39.5 months (range 2-114 months). In phoniatric evaluation most (six of eight) patients with fair voice outcome could not produce high pitched voices because of inability to stretch the vocal folds.
It is a common experience that vocal quality changes during a break in vocal loading. The purpose of the present study was (1) to analyse the effects of a short post-loading vocal rest in terms of changes in a large variety of voice parameters and (2) to assess the possible effects of gender and exposure factors on these changes. The voices of a randomly chosen group of 40 female and 40 male young students were loaded by having them read aloud a novel. Two sets of voice samples were recorded: a post-loading sample after three times 45-min vocal loading during the morning and a post-resting sample after a 45-min lunch break. The material recorded consisted of /pa:ppa/ words produced normally, as softly and as loudly as possible in this order. 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, closing quotient (ClQ), speed quotient (SQ), fundamental frequency (F₀)], amplitude-domain parameters of the glottal flow [glottal flow, minimum of the first derivative of glottal flow, amplitude quotient (AQ)], intraoral pressure and sound pressure level (SPL) values of the phonations were analysed. Voice range profiles and the singer’s formant (g/G, a/A, c∣/c, e∣/e, g∣/g for females/males) of the loud phonations were also measured. The subjects were divided into eight exposure groups (5 females and 5 males per cell) according to different combinations of the following exposure factors: (1) low (25 ± 5%) or high (65 ± 5%) relative humidity of ambient air, (2) low [<65 dB(A)] or high [>65 dB(A)] speech output level during vocal loading and (3) sitting or standing posture during vocal loading. Statistically significant differences between the post-loading and post-resting samples could be observed in many parameters (the values of intraoral pressure in the soft phonations decreased, the values of SPL and SQ in the normal phonations decreased and the values of AQ, F₀ and ClQ in the normal phonations increased). Most of the differences reflected a shift towards softer phonation. Gender and exposure factors also had significant effects.
In the first part of the study, the subjects (4 females, 4 males) produced sustained breathy, normal and pressed types of phonation. The maximum AC flow (fac) and the negative peak amplitude (dmin) of the first derivative of the glottal flow were extracted from glottal volume velocity waveforms estimated by inverse filtering. The ratio between fac and dmin (amplitude quotient, AQ), which gives an estimate of the closing time of the glottal flow, and its normalised version (NAQ) were computed. The NAQ values correlated strongly with the closing quotient of glottal flow. In the second part of the study, the aim was to investigate the dynamic extremes of the human voice in terms of F₀, SPL, fac, dmin, AQ and NAQ as well as the intraoral pressure (p) used for subglottal pressure estimation. Eleven normal subjects (5 females, 6 males) participated in this experiment. The subjects started with the production of soft phonation (approximately 55 dB at 40 cm) and increased their vocal intensity at 5-dB steps up to the level of 105 dB. At the analysis stage, the voice samples were divided into three categories: soft (<70 dB), normal (70–90 dB) and loud (>90 dB). In soft and normal phonation, intensity change was correlated with changes in the shape of the glottal flow waveform, whereas the loud voice samples showed a large increase in F₀ and p values. At the loudest extreme, dmin approached its maximum and AQ its minimum values and NAQ started to rise. In terms of the NAQ values of stressed syllables, the type of phonation was breathy in the soft intensity category, whereas in the normal and loud intensity categories it was within the range of the pressed type of phonation of sustained phonation samples.
In the production of voiced speech the main excitation of the vocal tract occurs during the glottal closing phase when the rate of change of the flow reaches its absolute maximum. The level of this maximum, the negative peak amplitude of the differentiated glottal flow, correlates strongly with sound pressure level. This study presents a straightforward method that yields a numerical value to characterize the effect of the main excitation on vocal intensity. The method, energy ratio by modified excitation (ERME), utilizes the glottal flow and the vocal tract transfer function estimated by inverse filtering and it synthesizes two signals based on the linear source-filter theory. The first sound is produced using the glottal flow given by inverse filtering per se. The second signal is synthesized by removing the main excitation from the differentiated flow. ERME is defined as the ratio between the energy of the first synthesized signal and the energy of the second one. It is shown that when the loudness of speech increases, the value of ERME first rises but in the case of very loud voices it starts to decrease. Hence, ERME shows that effects of secondary excitations of the vocal tract that occur during glottal opening become important in the production of very loud voices.
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