Temporary threshold shift frequency profiles after low-tone exposure.

Low-tone exposure elicits four distinct dips in hearing thresholds: one octave above the exposure frequency, in the permanent threshold shift (PTS) range, at about 10-11 kHz, and at 14-15 kHz. While dips 1, 2 and 3 decay as a function of the time log, dip 4 has a much longer decay time.