LTAS criteria pertinent to the measurement of voice quality

Abstract

Earlier attempts to establish LTAS criteria to quantify pathological voice qualities in dysphonic patients have mainly centered on organic voice disorders or qualities signalling organic lesions, like breathiness or roughness. The present investigation emphasizes qualities of disturbed voice due to aberrant function in organically healthy vocal organs. The same passage of continuous speech was produced by 10 experienced voice therapists in four different recognizable voice qualities. The speech samples were analysed by means of a commercially available narrow band analyser with a facility to produce long time average spectrograms. Using a personal computer connected to the analyser, a number of criteria were tested to differentiate among the voice samples. From the results it can be concluded that criteria expressing the slope of the LTA-spectrum or the energy ratio between the fundamental and first formant regions differentiate with statistical significance between samples of systematically different voice quality. However, there is also a substantial influence of voice intensity on the LTAS configuration, and the noted differences were in the magnitude of only 3–6%. Furthermore, inter-individual differences between LTA-spectra seem to be substantial.