Abstract:

A noninvasive ultrasonic measurement system was used to measure the amplitude and phase response of the peripheral auditory organs of the goldfish, considered auditory specialists, and the oscar, having an auditory threshold noticeably higher than that of the goldfish. The fish were excited with an underwater acoustic source at frequencies ranging from 12.5--3000 Hz. For frequencies between 12.5--400 Hz, tests were performed in a 14-m acoustic waveguide. For tests above 400 Hz, a 2.43-m-diam pool with a depth of 0.4 m was used. The response of the goldfish swimbladders, Weberian ossicles, and otoliths were measured. In addition, the swimbladders were deflated and measurements were made of the Weberian ossicles and the otoliths. Similar measurements were obtained for the auditory organs of the oscars, which vary from the goldfish in that they contain only one swimbladder and lack the Weberian apparatus. Comparisons within and between species are presented based on these four groups of data. [Work supported by ONR Grant No. N00014-94-1-0337.]