ASA 125th Meeting Ottawa 1993 May

3aPP7. Performance of a liquid-filled audio transmission line.

J. Phil Mobley

House Ear Inst., 2100 W. Third St., Los Angeles, CA 90057

Samuel Gilman

Sam Gilman Assoc.,

W. Los Angeles, CA 90025

The acoustic characteristics of a liquid-filled transmission line have been investigated over the range of 32 Hz to 12.5 kHz. As described in the accompanying paper ``Liquid transmission of sound directly into the cochlea,'' this method has been investigated to the transmission of audio sound through a scale model of the system. Measurements of dynamic range, frequency response, and distortion were made on an acoustic coupling system consisting of a cylindrical piezoelecric transducer (operated in a radial mode) coupled with a liquid-filled transmission line. When compared with similar methods of transmitting sound into the cochlear such as electromagnetic transducers, mechanical vibrators driving the ossicular chain, and bone conduction transducers, the liquid transmission method shows superior performance. Signal-to-noise ratios range up to 60 dB, frequency responses were flat ((plus or minus)5 dB) over 150- to 6000-Hz range, and distortion measured as low as 0.2% using a 1-kHz fundamental and ten harmonics. These measurements were made at SPL levels exceeding 140 dB using an identical piezoelectric transducer as a receiver terminated with simulated cochlear load.