Sounds situated in a certain domain of intensity can evoke auditory system physiologically. Permanent and continuous stimulation which is produced by such sounds would not be harmful to hearing organ.  This safe intensity is estimated 61 dB SPL. However one should pay attention that in case the intensity of mechanical sound wave increases (more than 75 dB SPL), the exposure time should be decreased unless the serious harm to auditory system is expected.  Auditory system can be affected due to sound harms in two major types: Permanent threshold shift and temporary threshold shift which can be described as the changes in hearing status of human caused by the exposure to sententorian sounds. Numerous physiological factors can exacerbate the devastating effects of sounds that we are aimed at an overall description on this issue in the present review article.

Method & Material: This study was performed on 36 normal-hearing subjects aged 18-25 years for survey of temporary threshold shift (TTS) by transient evoked otoacoustic emissions. Finding: Noise can affect the pure-tone thresholds and (TEOAEs) amplitudes. When cochlea affected by noise, evaluating TEOAE is more suitable than pure-tone audiometry. Because of this test, is objective an unaffected by attention and alertness and can be evaluated in difficult to test subject and also have high carefulness and can be performed in a quiet, but not sound-proof room.