Critical Bandwidth in Other Species

Abstract

The hypothesis was offered some years ago (Greenwood, 1961) that critical bandwidth in man was an exponential function of distance on the basilar membrane. Integration of the function yielded directly a frequency-position curve fitting Békésy's data. Thus critical bandwidth in man was apparently proportional, and if distance was scaled in millimeters, numerically equal, to the derivative of the frequency-position function. It was unlikely, however, that critical bandwidth would correspond to the same distance in species with cochleas of different sizes. Scale relations between frequency-position functions of a few species, and between displacement envelopes in four species (Greenwood, 1962), suggested that critical bandwidth might correspond to scale-related distances, implying changes among species in the constant of proportionality to the derivative of the frequency-position function. Based on a 1-mm distance in man, some unpublished calculations of scaled distances were made for other species. Subsequently, a revised CB function was suggested for man (Greenwood, 1971) in which critical bandwidth corresponds to 1.25 mm. Based on this distance, scale-related functions are suggested for cat, squirrel monkey, and guinea pig in which critical bandwidth corresponds, respectively, to distances of about 0.78, 0.71 +, and 0.61 mm. These values may be related to distance measures derived from physical and physiological data in those species.