HOW ACTIVE NOISE REDUCTION (ANR) IN AVIATION HEADSETS WORKS
Headphones are a pair of small electronic devices designed to be worn, over the head, into the user's ears, to listen to sound. In the aviation sub-sector, manufacturers developed a headphone technology that reduces unwanted noise using active noise reduction (ANR) to achieve a quieter flight environment. Noise-reduction headphones are designed to neutralize low-frequency engine and travel noise in aircraft. Basically, when you wear a headset while flying, this technology controls the reduction of ambient sound in two ways:
Passive noise control: The body of the earphone is used to protect against unwanted sound, either in or over the ear. Most headphones also depend on sound-proof mechanisms to prevent higher-frequency noise from reaching the ear. Active noise control: This method makes use of acoustic components like microphone, amplifier, and speaker to isolate ambient sound without affecting the desirable sound. ANR technology achieves isolation of sound that creeps into the ambience with the aid of the following:
1. Microphones to pick up ambient noise.
2. Electronics that match the sound and create an opposite sound.
3. Speakers that produce the opposite signal into the ear cup to cancel out unwanted noise.
These actions as performed by these components are simultaneous.
In the aviation environment, ANR is a technology that makes hearing of in-flight important information like safety announcements easier. The ANR technology works in such a way that unwanted sound is reduced by the addition of another sound specifically to cancel out the unwanted one. Analog circuits or digital signal processing is used in achieving modern active noise control. The waveform of the background noise is analyzed through adaptive algorithms, and then the generated signal will either isolate or invert the polarity of the original signal. The inverted signal is then amplified and a transducer creates a sound wave directly proportional to the amplitude of the original waveform.
The effect creates a destructive interference. Thereby, the volume of ambient noise is effectively reduced. ANR seeks to reduce sound emissions, for the personal comfort of the traveler, or due to issues of environmental considerations or legal compliance. However, noise-control headphones have the following drawbacks:
They cost more than regular headphones.
ANR relies on power source usually enhanced through a USB port or a battery that must be replaced or recharged periodically. The size and weight of the ANR headphones, compared to regular headphones, increases with the addition of battery and electronics as supporting components, thereby posing carriage issues. Clearly, ANR technology is able to do less when passive noise control provided by the ear cups is effective. The degree to which manufacturers are able to get a right blend of the passive noise control devices and ANR technology will determine acceptance of their products. It is a question of personal preference what choice of headset to make. Though, higher-end headsets tend to be very comfortable whilst reducing ambient noise, there is no one headset that works best for every head.
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