Threshold shift permanent

Permanent Threshold Shift Continued exposures to noise that produce TTS will cause a permanent decrease in hearing sensitivity and elevate the hearing threshold. Long-term exposure produces permanent threshold shift... 

Exposure to noise levels of about 90 dBA for even a few minutes may induce a temporary threshold shift (change of the threshold at which sound can just be heard), lasting from seconds to hours, and which can be detected by audiometry. Temporary threshold shift (TT5) may be accompanied by noises in the ears (tinnitus) and may be a warning sign of susceptibility to permanent threshold shift (PTS) which is an irreversible deafness. 

Permanent threshold shift (PTS) Hearing loss with less than normal recovery. 

It is important to note that, if the level of noise exposure remains unchanged, noise-induced hearing loss will lead to a permanent threshold shift affecting an increasing number of frequencies. 

The relationship between noise exposure and Noise-Induced Permanent Threshold Shift (NIPTS) can be expressed in the relative standardised scale based on the ISO 1999 standard that allows to compare hearing status of subjects of different age and noise exposure (Dudarewicz et al.,... 

There are three principal categories of NHL (1) temporary threshold shift (TTS), (2) permanent threshold shift (PTS), and (3) acoustic trauma. TTS occurs when exposure to sound damages the organ of Corti and its receptor cells. However, if the exposure is of relatively short duration, hearing sensitivity returns to preexposure levels after a recovery period (Brauer 1994). PTS, on the other... 

As discussed in Section 13.3 concurrent exposure to noise and some organic solvents and solvent mixtures is ototoxic. Styrene is an example of an ototoxic compound, with exposures to it causing permanent hearing threshold shifts and outer hair cell damage. Ethanol alone does not affect auditory sensitivity, yet, when combined with styrene it induces hearing and outer hair cell losses in test animals in levels greater than those caused by styrene alone. The potentiation of the ototoxicity of styrene by ethanol is ascribed to the altering of styrene metabolism by ethanol. 15 ... 

---