Electroglottogram-Based Estimation of Vocal Economy: ‘Quasi-Output-Cost Ratio’

Impact stress (IS) has been regarded as the main loading factor in voice production. To quantify the cost of voice production, an output-cost ratio (OCR) was proposed, which concerns acoustic output (pressure P) in relation to IS: OCR = 20 log P<sub>sup</sub>/P₀ – 20 log IS/IS₀ [1,2]. IS is difficult to measure directly in humans. However, it has been found to correlate with closed quotient (CQ, closed time/period length) measured by electroglottogram (CQ<sub>EGG</sub>) [3]. The present study proposes a noninvasive estimate of OCR, the quasi-output-cost ratio (QOCR): (sound pressure level (SPL)/CQ<sub>EGG</sub>) × (period length (T)/T₀). T₀ is set at 0.005 for females and 0.01 for males, corresponding to the respective period lengths of the mean F₀ in female and male speech (i.e. 200 and 100 Hz). QOCR was tested for 62 healthy females (23 teachers, 18 university students with voice training and 21 without). The teachers had a higher QOCR than the students in loud speech, but QOCR did not correlate with symptoms of vocal fatigue after a vocal loading test. QOCR seems to be a promising tool to quantify vocal loading but naturally not vocal loadedness.