Excerpts from sustained vowels as well as pure‐tone bursts were used as input signals to the guinea pig's auditory nervous system. Single unit responses to these signals were recorded from the cochlear nucleus. The results indicated that a neuron's response pattern to a particular vowel was determined by the ratio of the vowel's spectral energy that fell within the excitatory and inhibitory areas of the neuron. Addition of energy in a neuron's inhibitory region resulted in major modifications in the response of the neuron to both vowels and sinusoidal inputs. Generally, the addition of inhibitory energy resulted in a “temporal sharpening” of the response pattern.