Double hearing protection and speech intelligibility-room for improvement

Area of Science:

• Acoustics
• Audiology
• Aerospace Medicine

Background:

• Double hearing protection is standard for aircrew in noisy aircraft, typically foam ear plugs under headsets.
• Aircrew report difficulties with speech intelligibility and intercom volume, despite research on normal-hearing individuals.
• Newer ear plug technologies, including hi-fi and custom-made options, aim to improve communication.

Purpose of the Study:

• To evaluate the impact of different ear plug types on speech intelligibility in helicopter noise.
• To compare custom-made and hi-fi ear plugs against traditional foam ear plugs and headset-only conditions.

Main Methods:

• Nine normal-hearing pilots were tested in a simulated BO-105 helicopter noise environment.
• Speech audiometry was conducted with headset only, and with three types of ear plugs under the headset.
• Testing was randomized, double-blind, and included subjective ratings.

Main Results:

• Foam ear plugs significantly reduced speech intelligibility.
• Hi-fi ear plugs showed moderate improvement over foam plugs.
• Custom-made ear plugs provided speech intelligibility comparable to the headset-only condition.

Conclusions:

• Custom-made ear plugs offer superior speech intelligibility in helicopter noise compared to conventional foam ear plugs.
• These custom plugs maintain noise protection while enhancing communication, presenting a viable alternative for aircrew hearing protection.