A portable system for physiological assessment of hearing in marine animals

Abstract

A compact field portable system has been developed and tested for presenting sound stimuli (20 Hz–200 kHz) and acquiring and analyzing sound and microvolt-level electrophysiological responses in marine animals. Stimulus sound is controlled for frequency, amplitude, duration, rise/fall times, interstimulus interval, phase, and masking noise. Analysis is by synchronous averaging, with artifact rejection, and is displayed, stored, and may be printed, if desired. The weather resistant system includes hardware based on a 486 with fast bus and software for presenting shaped tones and pulses, acquiring up to eight channels of data for display, storage, and analysis. The system includes all necessary functional units (suction cup electrodes, high gain (X500K) amplifiers, analog-to-digital and digital-to-analog converters, fiber-optic intermodule connection, computer with LCD screen that can be seen in bright sunlight, an internal 1.2-gigabyte hard disk, power amplifier, transducers, power source) and is constructed in a set of small cases that can be hand carried to remote sites. To date, the system has been used for hearing tests in dolphins, Tursiops, white whales, Delphinapterus, and a beached pygmy Sperm whale, Kogia. [Work supported by ONR.]