Correction of tape recorder distortion

The estimation of the glottal volume-velocity by linear predictive inverse filtering is shown to be severely affected by tape recorder distortion; so much so that the closed phase (if present) in the glottal volume-velocity may not be detectable. We describe and illustrate our method for correcting both the phase (the major contributor to the distortion) and the magnitude of the recorded speech signal. The procedure is to derive an inverse filter which compensates for the tape recorder distortion introduced during the recording process. We implement the correction digitally but an analog filter could be built. Examples of distortion correction are shown for square and triangular waves, real and synthetic speech, and laryngographic data. The effect of distortion correction on the estimate of the glottal volume-velocity obtained by inverse filtering is also shown.