A method is described for deriving the volume velocity waveform at the glottis during voiced speech by inverse-filtering the volume velocity waveform at the mouth. Unlike the previously used technique of inverse-filtering radiated acoustic pressure, this method provides a signal that is accurate down to zero frequency, not susceptible to low-frequency noise, and easily calibrated in amplitude by a constant air flow. The primary limitation is the need for a transducer that will measure volume velocity at the mouth with adequate fidelity. In this work, volume velocity was recorded from a specially designed circumferentially vented wire screen pneumotachograph mask which provided a time resolution of ½ msec, without serious speech distortion. Inversefiltered volume velocity was recorded with two adult male subjects for voicing in the modal register. Typical results are shown which indicate the way in which the glottal waveform varied with changes of fundamental frequency, subglottal pressure, and a dimension of voice quality related to the degree of compression of the vocal folds. Also considered are the effects of glottalsupraglottal acoustic interaction, and the effect on the glottal waveform of air displaced by the movements of the vocal folds. Subject Classification: 9.9, 9.3. Amplitude calibration, the third problem area, is difficult because it depends on an accurate and stable placement and orientation of the microphone with respect to the mouth.

Frequency of vibration has not been widely used as a parameter for encoding speech-derived information on the skin. Where it has been used, the frequencies employed have not necessarily been compatible with the capabilities of the tactile channel, and no determination was made of the information transmitted by the frequency variable, as differentiated from other parameters used simultaneously, such as duration, amplitude, and location. However, several investigators have shown that difference limens for vibration frequency may be small enough to make stimulus frequency useful in encoding a speech-derived parameter such as the fundamental frequency of voiced speech. In the studies reported here, measurements have been made of the frequency discrimination ability of the volar forearm, using both sinusoidal and pulse waveforms. Stimulus configurations included the constant-frequency vibrations used by other laboratories as well as frequency-modulated (warbled) stimulus patterns. The frequency of a warbled stimulus was designed to have temporal variations analogous to those found in speech. The results suggest that it may be profitable to display the fundamental frequency of voiced speech on the skin as vibratory frequency, thought it might be desirable to recode fundamental frequency into a frequency range more closely matched to the skin's capability.

A number of commercial devices for measuring the transverse electrical conductance of the thyroid cartilage produce waveforms that can be useful for monitoring movements within the larynx during voice production, especially movements that are closely related to the time-variation of the contact between the vocal folds as they vibrate. This paper compares the various approaches that can be used to apply such a device, usually referred to as an electroglottograph, to the problem of monitoring the time-variation of vocal fold abduction and adduction during voiced speech. One method, in which a measure of relative vocal fold abduction is derived from the duty cycle of the linear-phase high pass filtered electroglottograph waveform, is developed in detail.

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It has been shown previously that a mask-type wire screen pneumotachograph can be constructed with a time resolution of % msec. In this paper it is shown that with careful design a resolution of about % msec can be achieved. The various factors involved in optimizing such a mask are described. A major practical limitation in the design has been the need for a fast-responding differential pressure transducer to measure mask pressure; however, a simple electrical compensating network is described that allows the use of a nondifferential transducer. Also determined are the conditions under which breath moisture condensing on the wire screen affects the performance of the mask. An example is given of how a high-speed pneumotachograph can be used, with a measure of the pressure across a constriction in the vocal tract, to derive the time variation of the flow conductance and resistance at that constriction. The advantages of a high-speed pneumotachograph in laryngeal frequency extraction are also considered.