Comparison of inverse filtering of the flow signal and microphone signal

This study looks at two ways of extracting a glottal waveform from recorded speech. One way is to inverse filter the flow at the mouth. Another is to inverse filter the microphone signal. Theoretically, the microphone signal is considered to be the equivalent of a first order differentiation of the flow signal recorded at the lips. Recording the oral airflow is more complicated than the recording of a microphone signal, as it requires the use of a mask, with constant adjustments during the recording. Recording of the microphone signal is more straightforward for the experimenter and less intrusive for the subject. If the two inverse filtering procedures can be shown to produce similar glottal flow waveforms for both types of recorded speech, this would support the use of only the microphone signal for those types of glottal flow analysis where the DC component of the flow is not essetial, making voice source analysis applicable in less specialised situations. In this study, we used recordings of microphone signal and recordings of oral flow to compare the results of inverse filtering. A group of twenty subjects produced repetitions of the utterance /pae/. We recorded oral flow, EGG, and the microphone signal. The flow and microphone signals were analysed using an automatic inverse filtering program and values for parameters which are extracted from the source wave are compared. The results were not as similar as expected, although in some respects, they correlated well. This may be due to experimental design, the degree of insight of the subject into the voicing task, and the fact that the speech material used for the comparison was not identical.