Toward a standard for hearing conservation for underwater and hyperbaric environments.

Area of Science:

• Audiology
• Occupational Health
• Diving Medicine

Background:

• Underwater noise exposure for divers is a growing concern.
• Existing hearing conservation standards are designed for airborne noise and are not directly applicable to underwater environments.
• There is a lack of a comprehensive hearing conservation standard for divers exposed to intense underwater noise.

Purpose of the Study:

• To review theories of underwater hearing and empirical data.
• To identify requirements for a potential underwater hearing conservation standard.
• To highlight gaps in current knowledge and suggest areas for future research.

Main Methods:

• Review of three theories of underwater hearing: tympanic, bone-conduction, and dual path.
• Analysis of existing empirical data on underwater hearing.
• Consideration of factors such as hearing sensitivity, frequency and dynamic ranges, and non-auditory effects.

Main Results:

• No adequate theoretical basis exists to adapt current airborne noise standards for underwater use.
• Empirical evidence is insufficient to determine safe underwater noise levels, except within a narrow frequency range (1.5-3.5 kHz).
• Underwater hearing data suggests a broader frequency range is necessary for an effective standard compared to airborne noise standards.

Conclusions:

• Further research is essential to establish an appropriate underwater hearing conservation standard.
• Key research areas include the dynamic range of the underwater ear and effects of gas mixtures and pressures.
• Underwater noise may pose risks beyond hearing, including effects on other body systems and job performance.