Monaural chinchillas (15) were exposed to 50 impulses of either 158, 615, or 175 dB peak SPL. The impulses were generated by a spark‐gap source, which produced an impulse with a 40‐μsecAduration. Quiet thresholds were measured at 0.25, 0.5, 1, 2, 4, and 8 kHz, using the averaged evoked response technique. Recovery was monitored for 31 days and then the animals were sacrificed and their cochleas were analyzed using the surface preparation technique. The three exposures produced virtually no permanent threshold shifts (PTS) with the exception of 10–30 dB PTS in one animal in each of the 165‐ and 175‐dB groups. However, hair cell losses were seen in all three groups. The cochleagrams varied from low level scattered losses to lesions of the OHC that spanned a 4‐mm stretch in the base of the cochlea. The IHC losses were considerably smaller and more restricted. The audiograms do no necessarily reflect the state of the cochlea.