Permanent Threshold Shift

And how do I know if I had permanent damage hearing vs temp?

On exposure to noise, the sensitivity of the ear will diminish as a measure of protection. This process is regarded as a change in the threshold of hearing, which means that only sounds louder than a certain level will be heard. The displacement may be temporary, chronic or permanent.

The sensitivity of TS varies greatly from person to person, men are generally more susceptible to low frequency sounds, and women more susceptible to high frequencies. Sounds in the 2-6 kHz range seem to induce a greater temporary threshold shift (TTS) than other frequencies. Also called auditory fatigue. Compare: adaptation.

One of the reactions of the organism to loud sounds is a constriction of blood vessels (vasoconstriction) which reduces blood supply to reach the hair cells of the organ of Corti. The exterior styling of the hair cells respond primarily to low levels of noise intensity and thus are easily saturated by loud sounds, especially when their source of blood is reduced. There remain only the interior lines of hair cells work because they need a higher intensity for stimulation.

Thus, TTS implies a temporary hearing loss for low level sounds (somewhat analogous to the close protection of the iris in bright light and temporary desensitization resulting from low light levels). If the outer hair cells are not allowed to recover from periods of calm, they gradually lose their ability to respond and eventually die. TTS can also be accompanied by tinnitus, ringing in the ears. See also: recruitment.

Temporary Threshold Shift (TTS): During a short exposure to noise, most people experience an increase in hearing threshold disappear within 24 hours but can last as long as a week.

Permanent Threshold Shift (PTS) or noise-induced permanent threshold shift (NIPTS): After prolonged exposure to noise, can cause permanent hearing damage in the inner ear (see ACOUSTIC trauma, organ of Corti, presbycusis).

Chronic Threshold Shift or Shift composed Threshold: If exposure to noise occurs repeatedly without sufficient time between exposure to allow recovery of normal hearing TS, can become chronic and possibly permanent. This is a particular danger when people who work in noisy environments are exposed to noise before driving, at home and at places of entertainment (see SOCIOCUSIS).
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