Groups of monaural chinchillas trained in behavioral audiometry were exposed in a diffuse sound field to an octave-band noise centered at 4.0 k Hz. The growth of temporary threshold shift (TTS) at 5.7 k Hz from zero to an asymptote (TTS
∞
) required about 24 hours, and the growth of TTS at 5.7 k Hz from an asymptote to a higher asymptote, about 12–24 hours. TTS
∞
can be described by the equation TTS
∞
= 1.6(SPL-A) where A = 47. These results are consistent with those previously reported in this journal by Carder and Miller and Mills and Talo. Whereas the decay of TTS
∞
to zero required about three days, the decay of TTS
∞
to a lower TTS
∞
required about three to seven days. The decay of TTS
∞
in noise, therefore, appears to require slightly more time than the decay of TTS
∞
in the quiet. However, for a given level of noise, the magnitude of TTS
∞
is the same regardless of whether the TTS asymptote is approached from zero, from a lower asymptote, or from a higher asymptote.
Neonatal Sound Exposure During Respiratory Support
