The Effects of Post-Loading Rest on Acoustic Parameters with Special Reference to Gender and Ergonomic Factors

Abstract

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.

Vocal Impact of a Prolonged Reading Task at Two Intensity Levels: Objective Measurements and Subjective Self-Ratings

“…This investigation focuses on female subjects because they are known to be more sensitive to vocal load than males, 35,42 and have a higher prevalence of voice disorders. 27,30 The prolonged reading task took place in controlled laboratory conditions, despite of the fact that these experimental conditions do not reflect the real-life vocal use.…”

Loading-Related Subjective Symptoms during a Vocal Loading Test with Special Reference to Gender and Some Ergonomic Factors

“…The changes in several acoustic parameter values [6][7][8][9][10][11]; the general trend was shift toward hyperfunctional or more pressed type of phonation during vocal loading, whereas the lunch break had opposite effects. The aim of the present study was to observe the loading-related symptoms and the possible effects of gender and some exposure factors on the symptoms occurring during the test.…”

“…Many studies suggest that ambient air humidity affects various voice parameters [7,8,[10][11][12][13][14].…”

“…To the best of our knowledge, there are only four earlier studies on the significance of reading posture for voice production [7,8,10,11], although empirical evidence suggests that a proper body posture is important for voice production [20].…”

“…Therefore, the three exposure factors in this study have very close links to ergonomics. If ergonomics is defined in such a broad sense, even gender has Vintturi/Alku/Sala/Sihvo/Vilkman close links to ergonomics, because it affects the human vocal capacities [e.g., 8,10,11,22].…”