No abstract

This paper describes the development rationale and some of the operating characteristics of a piezoelectric transducer for ossicular chain activation. By utilizing a very thin, bimorph-type, flexure-mode piezoelectric transducer in a cantilevered configuration, relatively large displacements can be generated by very low activating voltages, typically less than 1 V to produce displacements corresponding to normal communication levels. Measurements of transducer activating voltage necessary to produce various levels of round-window cochlear microphonic (CM) are compared with tympanic-membrane sound-pressure levels necessary to produce equal round-window CM in response to pure-tone waveforms. Umbo displacements produced by the transducer are compared with umbo displacements produced by pure-tone sound fields down to displacement levels less than 10 Å, through the medium of constant round-window CM in guinea pigs. Other investigations have concerned the ability of the transducer to deliver complex signals to the ossicular chain.

Amplitude of the late components of the averaged auditory evoked potential increases as the time between repeated stimuli is increased up to 12 sec. The interspersal of tone bursts of different frequencies within the interstimulus time interval was investigated as a method for improving data acquisition rate without sacrificing response amplitude. Series of 500-, 1000-, and 2000-Hz tone bursts were presented singly and in combinations of two and three frequencies at repetition periods of 1 to 8 sec. Response records were sorted and averaged according-to stimulus frequency, yielding one, two, or three averaged evoked potential records. Experimental results indicate that data acquisition rate can be improved by serial presentation of different stimuli without significant loss of response amplitude. [This project was made possible through funds granted by the University of Southern Mississippi Faculty Research Council.]