ABSTRACT
Exposure to high noise over time will cause permanent hearing damage. High noise will reduce communications intelligibility and be of operational consequence. Exposure to high-level communications over time will cause permanent hearing damage. Exposure to aircraft noise may reduce speech intelligibility. Exposure to aircraft noise may cause noise-induced hearing loss. Communications signal can also cause hearing damage. Attenuation can be considered in three distinct regions: low frequencies, intermediate frequencies and high frequencies. Active noise reduction (ANR) is a supplementary electronic system incorporated into earmuff to provide additional attenuation. ANR system requires power supply; provided directly from aircraft or via man-mounted pack. Types of communication used are speech and non-speech. Requirement to relay speech/non-speech signals in aircraft clearly; intelligibility depends on signal to noise ratio, quality of microphone and transducers, quality of transmission system and noise level at talker and listener positions.
