Approximate Calculation of the Dimensions of Traveling‐Wave Envelopes in Four Species

Calculations were made of the dimensions of traveling‐wave envelopes in four species. The calculations were based on Bekesy's measurements of the tuning curves of single points on the basilar membrane of each species, and on four empirical functions, one per species, relating frequency to position of maximum amplitude on the basilar membrane. The functions were in approximate agreement with other observations by Bekesy. It was found that the distances over which a traveling wave damps from maximum amplitude to fractions of maximum amplitude—i.e., to one‐half maximum, to two‐tenths maximum, or to “zero” amplitude, respectively—appear to be approximately constant, independent of the position of maximum amplitude on the membrane. In comparing the traveling wave envelopes of the four species, elephant, man, guinea pig, and chicken, it was found that (1) the shape of a traveling‐wave envelope is quite similar among the four species, (2) the distance over which a traveling wave damps from maximum to “zero” amplitude is the greater the longer the basilar membrane, (3) this distance, in the species compared, seems to be an approximately constant fraction of the length of the basilar membrane, independent of the length of the membrane.