ABSTRACT
Before examining the specific role each channel plays in tactile perception, we must first address the general issue of how sensory channels facilitate the overall performance of a sensory system. Acoustic stimuli are processed through separate channels referred to as critical bands. Each critical band functions as a filter that passes only the frequencies falling within a relatively narrow range contained within the broader frequency range of an audible sound. Fletcher (1940) suggested that the auditory system contains a bank of such bandpass filters with overlapping frequency ranges. In attempting to detect a signal against a noisy background, an observer will attend to the filter (channel) with a center frequency closest to the frequency of the signal. It is through this channel that the signal is detected. The only noises that can potentially mask the signal being detected are the noise frequency components that pass through this channel. Thus, the filtering property of the channel serves to remove much of the broad-band noise, which, in the absence of the channel, would greatly compromise hearing. The detectability of the signal is limited only by the integrated energy of the frequency components of the noise that pass through the channel. Because of the filtering capacity of the channel, other frequency components of the noise do not contribute to the noise level within the channel, although they can contribute to the noise level within other channels.
