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document
Double hearing protection and speech intelligibility-room for improvement . INTRODUCTION Double hearing protection is used in many air forces around the world for protection in noisy aircraft environments , particularly in helicopters . The usual combination is foam ear plugs under headset or helmet muffs . Much of the research that spurred the introduction of foam earplugs indicated little change in speech intelligibility in persons with normal hearing . However , aircrew often complain about having to maximize intercom volume for speech understanding , causing a situation with no reserve volume and bad sound quality . In recent years , further developments have included so-called hi-fi plugs and custom made ear plugs which are claimed to improve speech communication . The aim of the present project was to investigate different types of ear plugs and their effect on speech intelligibility in helicopter noise . METHODS Each of nine normal-hearing pilot subjects were placed in an environment of recorded helicopter noise from a BO-105 helicopter . Speech audiometry was performed under four different conditions : headset only , and three different ear plugs worn under the headset . Fitting of the ear plugs was performed by an ear , nose and throat specialist to ensure similar conditions . The sequence of test conditions was randomized and double-blind . In addition , a subjective rating scale was used . RESULTS Wearing foam ear plugs under the headset decreased speech intelligibility dramatically . The " hi-fi " plug was somewhat better than foam plugs , and the custom made ear plug provided a speech intelligibility close to the headset-only situation . Subjective rating scores coincided with these findings . DISCUSSION In helicopter noise , custom made ear plugs may provide a much improved speech intelligibility over conventional plugs when worn under a headset , while maintaining improved noise protection over the headset-alone situation . Custom made ear plugs might therefore be a good alternative to other forms of enhanced noise protection in helicopters .
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Intervention_Other
an environment of recorded helicopter noise from a BO-105 helicopter
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Intervention_Other
Speech audiometry was performed under four different conditions : headset only , and three different ear plugs worn under the headset
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Intervention_Other
Fitting of the ear plugs was performed by an ear , nose and throat specialist to ensure similar conditions
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Outcome_Other
subjective rating scale
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Outcome_Mental
speech intelligibility
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Outcome_Mental
speech intelligibility
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Outcome_Other
Subjective rating scores
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Outcome_Mental
speech intelligibility
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Outcome_Mental
noise protection
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Outcome_Other
enhanced noise protection