Effects of Hearing Protectors on Speech Communication and the Perception of Warning Signals.

摘要

Because hearing protectors attenuate the noise and signal by equal amounts within a given frequency range, reducing both to a level where there is less likelihood of distortion, they often provide improved listening conditions. The crossover level from disadvantage to advantage usually occurs between 80 and 90 dB. However, hearing protectors may adversely affect speech recognition under a variety of conditions. For hearing-impaired listeners, whose average hearing levels at 2000, 3000, and 4000 Hz exceed 30 dB, certain speech sounds will fall below the level of audibility. Visual cues may decrease the disadvantage imposed by hearing protectors. However, the Occlusion Effect, which decreases vocal output when the talker wears protection, adversely affects the listener's speech recognition. The poorest performance occurs when both talkers and listeners wear protectors. Hearing protectors affect warning signal perception in a similar manner. Again the crossover level seems to be between 80 and 90 dB, and there is greater degradation for individuals with impaired hearing. Earmuffs appear to pose greater problems than plugs, and this is especially true of difficulties in signal localization. Earplugs produce mainly front-back localization errors, while earmuffs produce left-right localization errors as well. Earmuffs also drastically impede localization in the vertical plane. (KR)