Passive Or Noise Reduction – ANR, Whats The

Difference

Both passive and Active Noise Reduction are methods to cut down the amount of noise that will reach your ear when using aviation headsets. They use different methods to achieve this.

Passive:

Passive headsets use the design, fit and material of the headset to keep the noise level below a certain value. The material of the headset ear domes, the ear dome seals, which can be gel filled and the fit on the head are all taken into account to physically prevent sound from entering the ear.

ANR – Active Noise Reduction:

Active Noise Reduction Headsets use passive methods and electronics to further reduce the level of noise that enters the ear by sampling the ambient noise, inverting the waveform and re-broadcasting it directly through the headset ear pieces where it helps to cancel out the original noise. This can result in up to a doubling of the passive noise reduction.

However, Active Noise Reduction only reduces noise across a relatively small frequency band. These headsets work best at frequencies below about 400-450 Hertz. This represents the frequency range normal for speech. Propeller and engine exhaust noise is also within this region. Therefore, ANR systems offer a significant advantage over passive systems where noise from propeller and engines is apparent, such as open cockpits or where doors are usually open such as for para-drop activities. Higher frequencies are not affected, however, for example airflow noise.

The disadvantage of an ANR headset is that it will need a power supply to activate the electronics. This could be in the form of a 9v battery or an external panel-mounted dedicated power supply. If this power supply should fail or you use an ANR headset that needs an external power connector is an airplane that does not have one installed, then the AR circuitry will not work.

The headset then falls back onto a purely passive method of noise reduction.

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