Low-Frequency Auditory Characteristics: Species Dependence

The magnitude and phase characteristics of the sound pressure at the eardrum-to-cochlear microphonic potential transfer function were measured at low frequencies for four species: cat, chinchilla, guinea pig, and kangaroo rat. The former two and the latter two demonstrated radically different properties in both magnitude and phase response. It is suggested that, since at low frequencies the middle-ear transfer functions of these four species are similar, the discrepancies are caused by differing acoustic input impedances of the cochleas that are influenced by the physical dimensions of the helicotrema and of the cochlear spiral.