A self-controlled trial to evaluate the use of active hearing defenders in the engine rooms of operational naval vessels.
BACKGROUND
Active Hearing Defenders are established hearing protectors with in-built electro-acoustics that shut-off ambient noise while allowing effective communication between users.


METHODS
A blinded, self-controlled trial was conducted among naval servicemen to compare the effectiveness of two types of active hearing defenders (Howard-Leight Thunder TM and COM-55) in relation to passive hearing defenders in an operational environment.


RESULTS
Subjects felt that the active hearing defenders were more comfortable, durable, and that the active hearing defenders helped them work better. When subjects were tested with a speech discrimination battery (Central Institute of the Deaf, Spondee Word lists), there was a significant difference (p value of 0.04, using the Kruskall-Wallis ANOVA test) between the two active and the passive defenders. However, no significant difference was found between the two types of active hearing defenders.


CONCLUSIONS
Active hearing defenders are an acceptable and efficacious means of hearing protection in noisy environments.
Naval Medicine Hyperbaric Centre, Republic of Singapore Navy, AFPN 6060, 36 Admiralty Road West, Singapore 759960. mikeong@pacific.net.sg
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D000328:Adult; D004430:Ear Protective Devices; D006317:Hearing Loss, Noise-Induced / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008889:Military Personnel; D009784:Occupational Diseases / Q000517:prevention & control*; D012767:Ships; D012846:Singapore; D013063:Speech Discrimination Tests