In the mustache bat (P. p. r.), cochlear microphonic (CM) is sharply tuned at 61 kHz whileN1is tuned at 64 kHz. The amplitude of the CM evoked by a 61‐kHz signal increased and decreased exponentially at the onset and cessation of the stimulus, respectively. Its rise time, which affects the threshold of theN1, varied as a function of the stimulus frequency even for a constant rise time stimulus. The longer the CM rise time, the higher theN1threshold is. To eliminate the effect of the CM rise time on theN1tuning curve, the stimulus rise time was adjusted on the basis of single unit tuning curves and the CM rise time was kept constant. Then theN1tuning curve was measured and was found tuned at 61 kHz instead of 64 kHz. This indicates the difference in best frequency between the CM andN1is simply due to the properties of a sharply tuned resonator andN1, but not due to a mechanism comparable to lateral inhibition. [Work supported by NSF.]