Threshold shifts in chinchillas exposed to octave‐band noise centered at 125 Hz for three days

Maximum threshold shifts for exposures to octave bands of noise having center frequencies of 500–4000 Hz are found one‐half to one octave above the exposure‐band center frequency (Carder and Miller, J. Speech Hear. Res. 15, 603–623). Maximum threshold shifts produced by exposure to octave‐band noise centered at 63 Hz are found four to five octaves above the exposure‐band center frequency. The question arises as to the frequency at which the maximum threshold shifts occur to octave bands of noise with center frequencies between 63 and 500 Hz. The present experiment was conducted to provide such information. A group of four monaural chinchillas was exposed for three days to an octave band of noise centered at 125 Hz at an intensity level of 110 dB SPL (94 dBA). Maximum threshold shifts occurred at four and four and one‐half octaves above the center frequency of the exposure band, i.e., at 2000 and 2800 Hz.