Detection of scattered ambient noise by fish.

Abstract

It has been hypothesized that one role of the fish’s auditory system may be to detect and localize nearby fish by ‘‘imaging’’ ambient noise scattered by their swimbladders. This is analogous to the role of the visual system of most animals, where the relevant signal is ambient light scattered by objects rather than light emitted by luminous objects. A classical conditioning experiment has been performed which indicates that the fish auditory system is capable of functioning in this manner. The ambient noise was provided by a J-9 transducer driven by Gaussian noise. Scattering of ambient noise by the resonant swimbladder was simulated by applying a filtered version of the same Gaussian noise to a small spherical projector. The target strength and bandwidth of the scattered noise were controlled by the attenuation and passband of the filter. The fish was conditioned to respond to the presence of the signal from the spherical projector. Thresholds of simulated scattered noise as a function of range to the subject were measured for the species Carassius auratus (common goldfish). The fish’s ability to discriminate this signal is taken to be a measure of its ability to detect scattered ambient noise. [Work supported by ONR.]

The vibrational response of single-chambered fish swimbladders to low-frequency sound

“…The displacement data were related to the scattering cross-section by where a 0 is the radius of the scattering swimbladder, and k are the stimulus frequency and wave number, sb is the measured displacement, p inc is the incident acoustic pressure, and w c w is the characteristic impedance of water (Lewis, 1994). The data were then fitted to the generalized scattering cross-section function for a resonant scatterer: where 0 is the resonance frequency and Q is the quality factor.…”

“…The frequency response of a swimbladder was measured with the Non-invasive Vibration Amplitude Measurement System (NIVAMS) (Lewis, 1994). NIVAMS uses highly focused, low-power continuous wave ultrasound to probe the body of a fish in vivo.…”

Soundscapes and the sense of hearing of fishes

“…There has been only one experimental attempt to investigate this concept as applied to fishes (Lewis & Rogers 1992), based on some psychophysical work on goldfish by Fay et al (1983). Studies on humans show that when a flat spectrum white noise is added to a copy of itself with a small delay (as if there were an echo), the resultant signal (rippled noise, repetition noise, or cosine noise) has a pitch determined by the delay, for delays ranging from 0.5 to 50 ms (Yost et al 1978).…”

“…The echo delay (pitch for humans) is proportional to the object distance, and the "strength" of the rippled noise perception is proportional to the object's size or target strength. Lewis and Rogers (1992) hypothesized that a fish can detect a nearby fish through detection of the fish's resonant swimbladder reradiating the ambient noise, arriving at the receiver fish from a specific location and with a delay with respect to the ambient noise, much like an echo. Conditioning experiments using a sound source to simulate a swimbladder reradiating the noise confirmed this hypothesis.…”

Potential Uses of Anthropogenic Noise as a Source of Information in Animal Sensory and Communication Systems

“…Rather than being used for communication, it is possible that the fish use their sensitive hearing to exploit ambient noise information. Although this possibility has not been well investigated, Lewis and Rogers (1992) demonstrated fish have the potential to use ambient noise to detect other fish. They successfully conditioned fish to discriminate between artificial Gaussian noise fields; either without any scattering or with scattering similar to that which would occur from resonance in swim bladders (Lewis & Rogers, 1992).…”