Recent studies of temporary threshold shift (TTS) and permanent threshold shift (PTS) in animals

Area of Science:

• Auditory Science
• Toxicology
• Animal Models

Background:

• Excessive noise exposure causes temporary and permanent hearing loss in humans and animals.
• Previous research, including Kryter et al. (1966), established foundational knowledge on noise-induced hearing loss.

Purpose of the Study:

• To review major findings from laboratory studies on experimentally induced hearing loss in animal models since 1966.
• To consolidate current understanding of temporary and permanent threshold shifts caused by noise exposure.

Main Methods:

• Review of published laboratory studies on noise-induced hearing loss in animal subjects.
• Analysis of data concerning threshold shifts, asymptotic levels, and cochlear damage.

Main Results:

• Chinchillas are identified as the most suitable animal model for noise-induced hearing loss research.
• Continuous moderate noise exposure leads to asymptotic threshold shifts within 18-24 hours.
• Permanent threshold shifts (PTS) are influenced by noise level, frequency, and duration, with energy being a key factor below approximately 115 dB.
• Periodic rest periods significantly reduce hearing loss and cochlear damage compared to continuous exposure.
• Some periodic exposure schedules show initial increases in threshold shifts followed by recovery.

Conclusions:

• Noise-induced hearing loss is a complex phenomenon influenced by various exposure parameters.
• The chinchilla model provides valuable insights into the mechanisms of hearing loss.
• Intermittent noise exposure strategies can mitigate auditory damage.