Studies on the temporary effect of noise on the auditory function in man

Area of Science:

• Auditory Neuroscience
• Audiology
• Occupational Health

Background:

• Noise exposure can cause temporary threshold shifts (TTS), impacting hearing sensitivity.
• Understanding the origin and neural correlates of auditory fatigue is crucial for hearing conservation.

Purpose of the Study:

• To investigate the effects of fatiguing noise exposure on auditory pathway function.
• To analyze changes in electrocochleography (ECoG) and auditory brainstem response (ABR) parameters following noise exposure.

Main Methods:

• ECoG and ABR recordings were conducted on 22 normal-hearing individuals before and after exposure to octave band noise.
• Auditory Compound Action Potential (ACAP) latency and inter-wave intervals were measured.
• Stimulus-response functions were analyzed to assess changes in auditory processing.

Main Results:

• Noise exposure induced a temporary threshold shift (TTS) of up to 35 dB.
• A significant increase in ABR wave latencies and ACAP latency was observed post-exposure.
• Auditory pathway intervals (I-III, III-V, I-V, ACAP-V) remained unaltered.

Conclusions:

• Noise-induced auditory fatigue, as measured by TTS, originates within the cochlea.
• The findings suggest that TTS is a cochlear phenomenon transferred to auditory pathways.
• Individual sensitivity to noise, indicated by TTS variability, may not reliably predict permanent threshold shifts (PTS).