When a noiselike auditory stimulus is used to study the auditory nervous system, it is difficult to determine the evoked response dependency upon the transitory changes in stimulus intensity and upon its spectrum. This is particularly true when the noise intensity fluctuates, as in filtered white noise, for example. However, if a relatively long tone burst is briefly frequency modulated (FM) by noise, the tone‐noise and noise‐tone transitions occur with no SPL intensity fluctuation. The responses can then be ascribed solely to the spectral transitions. A series of experiments has been performed on awake cats subjected to such stimuli in which the noise bandwidth was varied. Responses to the tone‐noise transitions were obtained from epidural electrodes and were compared with responses to both pure‐tone bursts and FM bursts with the same envelope. Of considerable interest is the finding that for relatively large bandwidths, the response is greater to the tone‐noise transition than to onset of an FM noise burst with the same bandwidth. [Supported by the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]