Reports from this and other laboratories are summarized to the effect that pulse trains in the 3–4‐kHz region, with pulse duration ?1 sec and with on fractions up to 0.05, are habitable when presented a round the clock for weeks, and yield no TTS greater than can be borne, when the level does not exceed 85 dB SPL. For more onerous acoustic loads, a damage risk criterion of 80 dB should be set for long‐lasting continuous exposures. The ear is more susceptible to this sort of acoustic load than is any other system of the body, and can serve as an early warning device for potential damage to those systems.Subject Classification:[43]65.50,[43]65.64, [43]65.66.