**6. Discussion**

It has been shown that threshold shifts can occur in humans following exposure to noise levels between 90 and 125 dB SPL (8). A temporary threshold shift (TTS) may include a temporary reduction in hearing acuity, which may become evident within minutes after exposure but is usually reversible in time (this time is variable across individuals).

The underlying pathophysiologic changes involve cell death among various sensory and support cells in the inner ear, resulting from an oxidative stress reaction due to long-term overstimulation [15]. Given the similarities of the typical mammalian auditory system and specifically the canine versus human auditory systems, it is not unreasonable to imply that the triggering causes and attributes of the noiseinduced hearing loss would be similar if not identical to that of canines.

From a behavioral perspective, canine handlers reported that after touchdown during mission helicopter flights, their canines were not reacting to standard verbal commands, reducing the tactical effectiveness of the canines. Handlers reported that it appeared that the canine was either not listening, was seemingly disoriented, or not readily responding to verbal commands for various lengths of time, which seemed to be canine specific (personal communication). The dogs in this flight training did not show any disorientation but did not react in the usual manner to vocal command once exiting the helicopter. The flight time during this training was shorter than most mission flights. Given the average threshold shift shown by the test dogs in this study (approximately 30 dB nHL), it is reasonable to presuppose that the threshold shift played a significant role in this behavior.

Presently, the actual prevalence of hearing loss in MWDs is unreported or classified. Given the newly established baseline auditory testing for MWDs, these statistics will become available, thus allowing for longer service and care of the dogs.

*Canine Hearing Management DOI: http://dx.doi.org/10.5772/intechopen.105515*
