Acoustical responses and suppression-period patterns in guinea pigs.

Acoustic responses to short sound stimuli have been measured in the external ear canal of guinea pigs. Unequivocal responses had frequencies between 1.8 and 3.2 kHz, latencies (to their peak pressures) of 2.8 to 4.5 ms and sound pressures up to -10 dB SPL. A set of criteria was developed to clearly distinguish acoustical responses from after-resonances of the stimuli. Added phase-locked, very-low-frequency tones were able under some conditions to totally suppress the acoustical responses. The suppression-period pattern thus produced strongly resemble those obtained for man and the masking-period patterns obtained with human subjects.