NoiseGard active noise compensation is achieved by generating a signal identical in sound pressure level but exactly reversed in phase to the noise signal, the effect being that the out-of-phase signal cancels most of the noise signal.

Active noise compensation is accomplished in the following manner: Each earcup includes a microphone, a feedback control circuit, and a transducer to reproduce both the communication and the noise cancelling signal. The feedback control microphones sense the total sound pressure within each earcup resulting from both the desired radio signal from the receiver and the undesired noise that has come through the earcup. The microphone signal is amplified and the radio signal is subtracted from it. The remaining signal (noise) is then filtered and inverted and the radio signal is added back in. Eventually, the entire signal is amplified and fed back to the transducer in each earcup. Since the noise component of the signal is inverted, it cancels the noise signal coming through the earcup. The radio signal remains unaffected, as it was not processed through the cancellation circuits.

The diagram on the left shows noise compensation with NoiseGard: Passive hearing protectors effectively attenuate noise from the middle and upper frequency range, the effect decreasing sharply in the lower range. However, active noise compensation with NoiseGard combined with passive hearing protectors results in a reduction of noise of approx. 25 dB in the 25–500 Hz frequency range. The total attenuation resulting from active and passive noise compensation is about 30 dB over the entire audio range.

A 10 dB reduction in noise is perceived subjectively as a halving in volume. A further reduction in noise of 10 dB again results in a decrease in unwanted noise by 50 %.

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Sennheiser HMEC 460 manual
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HMEC 460 specifications

The Sennheiser HMEC 460 is a high-quality aviation headset designed for pilots and aviation enthusiasts who require exceptional sound quality and comfort during long flights. This product stands out in the crowded market of aviation headsets due to its advanced features, robust build quality, and impressive noise-canceling capabilities.

One of the most notable features of the HMEC 460 is its dynamic noise-canceling technology. This advanced system effectively reduces ambient noise, ensuring clear communication between the pilot and co-pilot, as well as between air traffic control and the aircraft. The headset operates at a high level of noise isolation, allowing users to focus on their duties without the distraction of background sounds. This is particularly important in aviation, where clear communication is critical for safety.

Comfort is another significant aspect of the HMEC 460. It features plush ear cushions and an adjustable headband, providing a snug fit without causing discomfort during extended use. The lightweight design further enhances the comfort level, making it ideal for long flights. The headset also includes a flexible microphone boom, which can be positioned for optimal voice clarity while minimizing wind noise.

The build quality of the Sennheiser HMEC 460 is robust, designed to withstand the rigors of the aviation environment. The materials used in construction are durable yet lightweight, ensuring longevity and reliability. Additionally, the headset incorporates a shielding design that protects against electromagnetic interference, which is crucial when flying in aircraft equipped with various electronic systems.

In terms of connectivity, the HMEC 460 has a versatile plug-and-play design, making it compatible with a wide range of aircraft intercom systems. This adaptability extends its usefulness across different aircraft types and flight scenarios. The headset also has a mono/stereo switch, allowing pilots to choose the audio output mode based on their preference and the specific requirements of their aircraft.

In summary, the Sennheiser HMEC 460 is a sophisticated aviation headset that combines comfort, high-quality sound, and advanced noise-canceling technology. With its durable design and compatibility with various intercom systems, it has become a favorite among pilots seeking a reliable, high-performance headset for their aviation needs. Whether flying for leisure or professionally, the HMEC 460 enhances the experience by providing clear communication and exceptional comfort in the cockpit.
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