The use of fundamental frequency raising as a strategy for increasing vocal intensity in soft, normal, and loud phonation

A method is presented to estimate the effect of intentional raising of fundamental frequency (F0) on vocal intensity. The method, Energy of the Synthesised Period (ESP), is based on computation of the energy of a hypothetical speech sound synthesised using a single period of the glottal volume velocity waveform and a digital filter that models the vocal tract. Both the glottal flow and the vocal tract filter are estimated by inverse filtering. The results show that, in producing loud voice, speakers use F0 to increase the number of glottal closures per time unit, which increases rapid fluctuations in the speech pressure waveform, which, in turn, raises vocal intensity. The average increase of sound pressure level due to this active use of F0 was approximately 4 dB in loud speech.