Frequency selectivity in the parakeet (Melopsittacus undulatus) studied with narrow-band noise masking

Narrow-band noise masking was studied in the parakeet (Melopsittacus undulatus) using a modified method of limits and an instrumental avoidance-conditioning procedure. Masked thresholds were obtained from five subjects at 10 frequencies between 0.5 and 5.0 kHz for each of four sensation levels (26, 46, 66, and 86 db) of a 1/3-octave band noise masker centered at 1.6 kHz. The amount of masking was found to be linearly related to noise level, and the shape of the masking curve was symmetrical on both sides of the center frequency of the masker. In all cases, the greatest threshold shift occurred at the center frequency of the masker. The relative symmetry of the parakeet narrow-band masking curves contrasts with masking results reported in mammals.