Critical bandwidth in loudness summation in sensorineural hearing loss.

Critical band estimation was performed in thirty-three patients with sensorineural hearing loss by the method of loudness summation, using noise bands centred around 1 kHZ. In 17 patients the hearing loss was of hereditary origin, in 16 patients of various, mostly unknown, origin. The normal loudness difference between broad band noise and narrow band noise decreased with increasing hearing loss, most pronounced in recruiting ears. Judged individually, 1/3 of the patients appeared to have a widened critical band, but several biases appeared to be responsible for these results. The pooled data indicated a normal critical band, both in patients with hearing losses less than 50 dB HL and in patients with hearing losses greater than or equal to 50 dB HL. Based on this finding, the validity of the critical band as a measure of the frequency selectivity of the ear is discussed and a theory is proposed for the anatomical and functional correlate of the critical band in loudness summation.