Abstract
Twenty patients with presbycusis and a rather flat audiometern pattern had critical band estimation performed by the method of loudness summation, using noise bands centred around 1 kHz. The pooled data indicated a normal critical band both in patients with a hearing loss < 50 dR HL and in patients with a hearing loss <50 dB HL. The normal loudness difference between broad band and narrow band noise was reduced at all levels except the highest, giving rise to very flat CB functions. This reduction was more pronounced at the highest test levels in recruiting ears than in non-recruiting ears. A theory is suggested for parts of the anatomical and psysiological correlate of the empirical phenomenon, the critical band.