Acoustic intensity limens in the goldfish.

Abstract Thresholds for acoustic stimuli and discrimination limens for different acoustic intensities were obtained in the goldfish, Carassius auratus, by means of avoidance conditioning techniques. The audiogram for this species, based on mean thresholds determined by the staircase audiometric method, ranged from about −25 dB (re 1 μb) at 50 Hz to a low point of almost −46 dB at 500 Hz and rose to −2 dB at 2000 Hz. Above this point the audiogram rose sharply and the practical limit of hearing was at 3000 Hz with a threshold value of about +22 dB. Comparison with other species showed that the sensitivity and frequency range of the goldfish, as well as of other ostariophysine species (possessing a Weberian apparatus), were significantly greater than in other teleosts. Based upon measurements of ambient noise, it was assumed that these threshold values were not masked by external noise. Goldfish were found to be capable of discriminating the intensity of two pure tones when the difference between the two was from 3 to 6 dB of acoustic pressure. Over a range of 30 dB there was no significant difference in the discrimination limen. This limen is smallest in the 300 to 400 Hz range and increases sharply above 1000 Hz. The upper limit of any frequency discrimination is about 1500 Hz. Comparisons of these data with mammalian auditory capacities show both quantitative and qualitative differences, and the problem of distinguishing between the pressure (far-field) and displacement (near-field) reception is discussed.