The self-to-other ratio applied as a phonation detector for voice accumulation

A new method for phonation detection is presented. The method utilises two microphones attached near the subject's ears. Simplified, phonation is assumed to occur when the signals appear mainly in-phase and at equal amplitude. Several signal processing steps are added in order to improve the phonation detection, and finally the original signal is sorted in separate channels corresponding to the phonated and non-phonated instances. The method is tested in a laboratory setting to demonstrate the need for some of the stages of the signal processing and to examine the processing speed. The resulting sound file allows for measurement of phonation time, speaking time and fundamental frequency of the subject and sound pressure level of the subject's voice and the environmental sounds separately. The present implementation gives great freedom for adjustment of analysis parameters, since the microphone signals are recorded on DAT tape and the processing is performed off-line on a PC. In future versions, a voice accumulator based on this principle could be designed in order to shorten analysis time and thus make the method more appropriate for clinical use.