No abstract

In seeking an acoustic description of overloaded voice, simulated environmental noise was used to elicit loud speech. A total of 23 adults, 12 females and 11 males, read six passages of 90 s duration, over realistic noise presented over loudspeakers. The noise was canceled out, exposing the speech signal to analysis. Spectrum balance (SB) was defined as the level of the 2-6 kHz band relative to the 0.1-1 kHz band. SB averaged across many similar vowel segments became less negative with increasing sound pressure level (SPL), as described in the literature, but only at moderate SPL. At high SPL, SB exhibited a personal "saturation" point, above which the high-band level no longer increased faster than the overall SPL, or even stopped increasing altogether, on average at 90.3 dB (@30 cm) for females and 95.5 dB for males. Saturation occurred 6-8 dB below the personal maximum SPL, regardless of gender. The loudest productions were often characterized by a relative increase in low-frequency energy, apparently in a sharpened first formant. This suggests a change of vocal strategy when the high spectrum can rise no further. The progression of SB with SPL was characteristically different for individual subjects.

The aim was to investigate how female patients with vocal nodules use their voices when trying to make themselves heard over background noise. Ten patients with bilateral vocal fold nodules and 23 female controls were recorded reading a text in four conditions, one without noise and three with noise from cafés/pubs, played over loudspeakers at 69, 77 and 85 dBA. The noise was separated from the voice signal using a high-resolution channel estimation technique. Both patients and controls increased voice sound pressure level (SPL), fundamental frequency (F0), subglottal pressure (Ps) and their subjective ratings of strain significantly as a main effect of the increased background noise. The patients used significantly higher Ps in all four conditions. Despite this they did not differ significantly from the controls in voice SPL, F0 or perceived strain. It was concluded that speaking in background noise is a risk factor for vocal loading. Vocal loading tests in clinical settings are important and further development of assessment methods is needed.

No abstract

In some professions, workplace noise appears to be a hazard to the voice, if not to hearing. Several studies have shown that teachers and sports instructors, for example, are more prone to voice problems than average, prompting research on loud voice. Since on-location recordings are in many ways impractical, the running speech of 23 untrained speaker subjects (12 female, 11 male) was instead recorded in several types of loud noise that was presented over high-quality loudspeakers. Using adaptive cancellation techniques, the noise was then removed from the recordings, thus exposing the strained voices for analysis. The experiment produced a large body of data, only one aspect of which is reported here. In most subjects, the vowel spectrum as a function of voice SPL showed the expected behavior for low to moderate efforts, but developed a very pronounced peak in the F1 region at the highest efforts. This peak can be ascribed to the concerted action of several acoustic mechanisms, including source waveform asymmetry, F1 approximating one of the lower partials, and increased formant Q values due to a longer closed phase. [Work supported by the Swedish Council for Working Life and Social Research, Contract No. 2001-0341.]