It has been suggested that humans discriminate different frequency sounds with greater selectivity than other mammals. However, mechanisms that could underlie higher frequency selectivity in humans are unclear. Recent studies show that the tectorial membrane (TM) supports longitudinally propagating waves, and the spread of excitation of these TM waves has been implicated in controlling the tuning properties in a mutant mouse model of hearing. Here we compare TM morphology and waves in humans and mice and show that despite some differences in morphology, the spread of excitation of TM waves is similar in spatial extent. However, the cochlear maps of humans and mice differ significantly, with similar cochlear distances mapping to a narrower range of best frequencies in humans than in mice. By coupling different frequency ranges, TM waves could contribute to differences in frequency tuning in mammals, with the smaller human range of frequencies corresponding to sharper frequency tuning.