Studies of the Critical Band from a Audiological Angle

Abstract

This study was designed to find out physiological background of the critical band proposed by Fletcher (1937) through psychoacoustic procedures. In this report the critical band could be interpreted in terms of spatial summation on the assumption that the critical band was related to neural information sent to the brain by some of the nerve patches as physiological background. Especially, the authors tried to clarify on anatomical level where spatial summation is performed. In this study, post-stimulatory facilitation, monaural power summation and binaural power summation were used as psychoacoustic method of measurement, and were performed both in normal and impaired ears. The results obtained were as fallows:
1) It would be made clear that the frequency range over which spatial summation was performed coincided approximately with Fletcher's critical bandwidth.
2) It was found that binaural summation could be considered to be negligible in psycholological measurement.
3) It could be inferred that spatial summation phenomenon was reflected in form of vibration along the basilar membrane with sinusoidal stimulus.
4) It could be assumed that Fletcher's critical band as well as spatial summation was psychoacoustical phenomenon caused by the action of synapse at the lower anatomical level than the primary auditory neuron.