Clinical psychophysics. Illustrated by the problem of auditory overload

In some patients with sensorineural hearing loss, masking extends over an abnormally wide range toward the higher frequencies. Most likely the main determinant is excessive harmonic distortion. Under this assumption, the masking measured with a probe tone at 2 kHz, due to a masker tone of 1 kHz, should be dependent upon the phase of the probe tone. This has been confirmed experimentally; it proved possible to derive the strength and phase of the equivalent second harmonic from the data. For normal ears, the strength was found to depend upon the SPL of the masker in the expected, quadratic manner. The phase was found to exhibit a startlingly rapid transition over nearly 360 degrees within one octave (500-1 000 Hz fundamental). Results of clinical measurements with the same method will be discussed.