ASA 125th Meeting Ottawa 1993 May

4aAB5. Measurement and analysis of the two-peak resonance of fish swimbladders.

Wen-xu Zhou

Peter H. Rogers

School of Mech. Eng., Georgia Inst. of Technol., Atlanta, GA 30332

The object of this research is to study the frequency response of the two-chambered goldfish swimbladder. An ultrasonic system was devised to measure swimbladder frequency response in vivo in a noninvasive, nonintrusive manner. Measurements were also made for oscars which have a single-chambered swimbladder. Unlike the oscar, two peaks often appear in the response curves of goldfish. To explain this two-peak resonance, an experimental model and an analytical model have been developed. The experimental model employs two gas bubbles to simulate the swimbladder. The experimental results show that the interaction between the two chambers of the goldfish swimbladder causes the two-peak phenomenon. The analytical model treats an oscillating system with two degrees of freedom. The parameters for the analytical model are related to the physical parameters of the system by theory. From comparison of the experimental and theoretical models, it is found that the damped-spring-mass system with two degrees of freedom reproduces what has been observed in the two-bubble experiment and does a reasonable job of modeling the two-chambered goldfish swimbladder.