Tone-on-tone masking in subjects with normal hearing and with sensorineural hearing loss.

Quiet and masked thresholds were obtained from 5 subjects with normal hearing and 31 subjects with sensorineural hearing loss. Maskers were pure tones varying in frequency and intensity. The hearing-impaired subjects showed an abnormal spread of masking when masking was measured in terms of masked threshold. The abnormal spread of masking seems to be related to both the hearing threshold of the masker and the quiet threshold of the test signal. The notch due to detection of combination tones found on the high-frequency slope of masked audiograms of normal subjects (obscuring the actual extent to which the signal is masked) tends to accentuate the apparent abnormal upward spread of masking in the hearing-impaired subjects. The abnormal spread in the latter case is real, but comparison with the normal case must take the notch into account.