Long-term average spectra of adult Iranian speakers' voice.

Summary Introduction Long-term average spectrum (LTAS) allows quantifying the voice quality and provides an overview of the mean spectral characteristics of a voice. The aims of this study were to survey normal spectral characteristics of Persian and investigate sex-related changes in the source characteristics of dynamic speech using LTAS. Method Speech samples obtained from 30 male and 30 female Persian-speaking participants reading a text in habitual pitch and loudness level. At the LTAS window and using Praat software, the amplitude values were obtained at equal intervals of 160Hz, ranging from 0 to 8kHz. Results The main features of the average spectrum were as follows: peak in the region of 480Hz with a reduction at higher frequencies, a 20dB decline from 480 to 960Hz, a flat region from 960 to 1920Hz, a further decline from 1920 to 3040Hz, and a further flat region from 3040 to 8000Hz. In comparison to men, women revealed significant lower levels of amplitude at frequencies of 160 and 320Hz and higher levels of amplitude at frequencies of 960, 3360, 3520, 3680, 3840, and 5920Hz. Conclusion The overall shape and gender-related energy distribution pattern of the LTAS of Persian were more similar to those of English than to those of Korean. The more phonetic differences between Persian and Korean compared with Persian and English might contribute to different spectral characteristics. The present study tried to clarify the spectral characteristics of Iranian male and female voices and focused on more breathy voice quality for women than men.