The effects of open throat technique on long term average spectra (LTAS) of female classical voices.

In the third of a series of studies on open throat technique, we compared long term average spectra (LTAS) of six advanced singing students under three conditions: 'optimal' (O), representing maximal open throat, 'sub-optimal' (SO), using reduced open throat, and loud sub-optimal (LSO) to control for the effect of loudness. Using a series of univariate repeated measures ANOVAs with planned orthogonal contrasts, we tested the hypotheses that sound pressure level (SPL) and the ratio of spectral energy in peaks and areas between 0-2 kHz and 2-4 kHz would be reduced in SO and LSO compared to O. There were significant differences between SO and LSO but hypotheses were not confirmed for O. These findings do not accord with differences in vibrato extent and onset between O and SO/LSO (Mitchell and Kenny, in press). These results suggest that while LTAS provides information on energy distribution, measuring spectral energy areas appears to be the most sensitive measure of energy distribution between conditions. Plotting the differences between O and SO/LSO pairs of LTAS clearly indicates the areas of spectral change. The findings from this study also indicate that LTAS are not sufficiently sensitive to measure vocal timbre as they were not consistent with perceptual or other acoustic studies of the same samples.