1. Behavioral thresholds were obtained from cats, first with only their right ear and right dorsal, intermediate, and ventral acoustic striae (DAS, IAS, and VAS, respectively) intact, and then again with only their right ventral acoustic stria intact. 2. Using usual definitions of "threshold" the loss of the dorsal and intermediate acoustic striae results in no measurable deficit in the detection of noises or tones on a silent background. 3. In sharp contrast, even partial damage of the ventral acoustic stria (i.e., trapezoid body section) results in marked deficits in sound detection. 4. Therefore, the ventral acoustic stria is both necessary and sufficient to maintain normal acoustical sensitivity. 5. However, loss of the dorsal and intermediate striae seems to result in a degradation of reliability in the detection of suprathreshold sounds--perhaps akin to a deficit in listening.