Long-term-average spectrum analysis of phonatory effects of noise and filtered auditory feedback

Using long-term-spectrum (LTAS) analysis of fluent speech, the effects of speaking in noise and of speaking with differently filtered auditory feedback as well as of voluntarily changing vocal intensity are analyzed in nine male adult singers and nonsingers. Three values in the LTAS are analyzed: the level of the main pedk near 500 HZ, of a secondary peak near 2000 Hz and at the average fundamental frequency. The level at 500 Hz was highly correlated with the equivalent sound level, with the average fundamental frequency and with the level of the peak near 2000 Hz. The singers were found to produce a higher sound level than the nonsingers under all conditions, and their voices contained stronger high-frequency components. Also, unlike the nonsingers they reduced vocal intensity when reading in silence with enhanced highfrequency components in the auditory feedback. The LTAS effects of noise and of auditory feedback filtering was found to be similar to those of the voluntary changes of vocal intensity for both singers and nonsingers. When the high-frequency components of the auditory feedback was enhanced during reading in noise, bath subject groups reduced vocal intensity. Introduction The loudness of speech tends to increase with the ambient noise level (Lane & Tranel, 1971). With regard to vocal abuse, clinicians discourage speaking under noisy conditions; this implies that speaking lcudly may be detrimental to vocal health. Concert and opera singers, and stage actors, often use their voices at loudness and pitch levels that would render untrained voices hoarse; yet they do not normally suffer vocal damage. Cne technique which enables singers to he heard without amplification over orchestras in large auditoriums is their emphasis of highfrequency energy, the so-called "singer's formant" which is a spectrum envelope peak near 3 kHz (Sundberg, 1974; Cleveland & Sundberg, 1983; Ebssing, Sundberg & Ternstrom, 1986). This singer's formant is usually a pronounced spectrum feature of the trained voice. However, a high average level of spectrum components in, or close to, the frequency * University of Southern California, Los Arqeles, CAI USA ** D e p t . of Phoniatrics, J33T Clinic, Malroij eneral Wspital