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Otorinolaringologia 2001 September;51(3):119-24


language: Italian

Possibility to value the noise induced hearing loss susceptibility using distorsion products

Giordano L., Canale A., Macchi E., Macocco G., Cavalot A. L., Ferrero V., Albera R.

Università degli Studi - Torino Dipartimento di Fisiopatologia Clinica II Sezione di ORL *Se.p.in.


Background. Noise induced hearing loss is consequent to high intensity noise exposure protracted in time. Not all subjects however present the same susceptibility to noise damage. This different susceptibility is influenced by causal factors and by contributory causes. In the past, many tests have been suggested in order to identify more sensible subjects to noise exposure; most important are those based on TTs. Unfortunately, this aim has not been achieved yet. Distorsion product otoacustic emission (DPOAEs) are actually considered to represent the active process of cochlear outer hair cells and can be applied as a useful, objective and non-invasive test to evaluate the cochlear function. For this reason DPOAEs are used to determinate infraclinical noise induced cochlear suffering. The aim of the study is to determine the distorsion products variation, due to noise, looking for different behaviour that can be traceable back to a different susceptibility to noise induced hearing loss.
Methods. In this comparative study 129 normally hearing subjects were submitted to pure tone audiometry (PTA) and DPOAEs recording at 4 KHz pre- and after 5’ 90 dB white noise acustic stimulation.
Results. The study shows that after acustic overload two possible DPOAEs modifications can be recorded. A reduction of DPOAEs amplitude was observed in 77 subjects (60%), and an increasing of DPOAEs amplitude in 52 subjects (40%) after 5’ 90 dB white noise acustic stimulation. Between the two groups there is not significant difference in the DPOAEs amplitude after the stimulation; otherwise there is a significant difference to Student “t” test (p<0.05) in DPOAEs before white noise acustic stimulation.
Conclusions. The study seems to confirm the possibility to distinguish two populations with a differrent behavior after white noise acustic stimulation, but it is very interesting to note that the group more subject to the noise induced hearing loss seems to be pointed out by the DPOAEs amplitude before the noise acustic stimulation.

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