Electroglottogram -based Estimation of Vocal Economy: “Quasi-Output-Cost-Ratio”

Anne-Maria Laukkanen, Elinita Mäki

Impact stress (IS) has been regarded as the main loading factor in voice production and the most plausible cause of vocal fold traumas like nodules. To quantify the cost of voice production, Berry et al. (1998, 2001) presented a parameter called output-cost-ratio (OCR), which concerns the acoustic output in relation to IS: OCV= 20 log P_sup / P₀ -20 log IS/IS ₀.
IS is difficult to measure directly in humans. However, it has been found to correlate with closed quotient (CQ, closed time / period length) measured from electroglottogram (CQ_EGG) (Verdolini et al. 1998). The present study proposes a simple noninvasively obtainable estimate of output-cost-ratio, the “Quasi-Output-Cost-Ratio” QOCR: [(Sound pressure level (SPL) / CQ_EGG ) x (period length (T)/ T₀)]. There T₀ was set to 0.005 for females and 0.01 for males, corresponding to the period length of the mean F0 in females’ and males’ speech respectively (i.e. 200 Hz and 100 Hz). In the present study, QOCR was calculated from the vowel portion of the loud syllable repetition on [pa:] for 62 healthy subjects (54 females, 8 males). Of the females, 24 were university students, 21 were teachers and 8 were actors. The subjects attended a 5 minute vocally loading test (counting numbers aloud at 90dB measured at a distance of 1 meter in a well-damped studio). Subjective reports of symptoms of vocal fatigue will be concerned in relation to the measured QOCR. Subject groups will be compared.

Keywords: impact stress, vocal loading, vocal fatigue.

Anne-Maria Laukkanen, Elinita Mäki
Department of Speech Communication and Voice Research
University of Tampere,
Tampere, Finland
Anne-Maria Laukkanen, Anne-Maria.Laukkanen@uta.fi