Automatic glottal inverse filtering

Early detection or abnormal laryngeal function is generally difficult with present techniques. The glottal volume-velocity (v-v) is an indicator of laryngeal function, but cannot be measured directly from acoustic speech because of vocal tract filtering. Digital inverse filtering is the basis for an automatic on-line method we have developed to determine the glottal v-v for normal and pathological speech. This method was developed by addressing four specific areas. First, the interval of the undriven vocal tract response during closed glottis is identified from an electroglottographic signal. Second, the vocal tract configuration is estimated by a linear prediction analyis of the closed glottis interval of the speech waveform. Third, low frequency noise is removed by a high pass filtering operation followed by a low pass compensation. Fourth, the low frequency, bias inherent in the process is removed.