Roaring aircraft engines and loud wind noise: the cockpit of an aircraft is dominated by high noise levels. NoiseGard™ technology from Sennheiser ensures relaxed flying and safe communication above the clouds. Now, the innovative and fully adaptive NoiseGard™ / digital system offers pilots even better noise-canceling performance.
During flying, a pilot’s hearing is under constant strain: from the roaring of engines when the aircraft is taking off to the monotonous engine noise at cruising altitude, accompanied by loud wind noise. Nevertheless, a pilot has to remain focused, and needs to clearly hear all voice communications. Therefore, noise-reducing headsets are essential in protecting the hearing, reducing stress and improving overall safety.
A headset provides passive attenuation of ambient noise by using noise-attenuating materials and a closed, circumaural design. In this context, a headset’s contact pressure plays an important part: the better the headphones fit against the head, the more effective the shielding against noise will be. With Sennheiser’s new S1 Digital headset, a special eye-glass comfort zone in the upper area of the ear cushions ensures that the headphones fit perfectly against the head even when the pilot is wearing glasses. The headset contact pressure can also be selected by the pilot to find the perfect balance between a comfortable fit and optimum passive noise attenuation. Passive noise attenuation provides an effective shield, particularly against high-frequency noise.
To reduce low-frequency noise, an acoustic trick is used, based on the physical principle of noise and anti-noise, which was researched for the first time by the physicist Paul Lueg in the early 1930s. Put simply, an artificially generated sound field that is phase-inverted to the sound field of the noise has the effect of canceling out the unwanted noise before it reaches the ear.
Sennheiser’s NoiseGard™ technology works as follows: miniature microphones integrated into the ear cups pick up the low-frequency noise close to the ears. Sophisticated electronic circuitry then calculates a sound wave that is phase-inverted by 180 degrees to the unwanted noise. Directly at the ear, the noise and anti-noise cancel each other out almost completely. As a result, particularly annoying low-frequency noise is dramatically reduced.
NoiseGard™ / digital is the next generation of Sennheiser’s NoiseGard technology. The fully adaptive digital noise reduction technology can be quickly optimized for changing noise environments by a touch of the button, taking into account the actual noise situation for the pilot. “Every aircraft is different, and so is the noise on board,” explains Joerg Buchberger, Business Segment Manager Aviation. “It depends on the engine, the noise of which will of course vary during the different phases of the flight, and on the acoustics within the plane.” Unlike analog noise compensation, which works with set filters, the fully adaptive NoiseGard™ / digital will measure the spectrum and intensity of the surrounding noise, once the pilot presses the Smart Update button.
At the core of the new noise canceling technology is a powerful digital signal processor, which generates a filter algorithm that specifically reduces the dominant noise spectrum. „By analyzing both the frequency band and the noise peaks, the filters can be perfectly adapted to the situation at hand,” says Jörg Buchberger. “In order to pick up the surrounding noise as accurately as possible we use two external and two internal microphones.”
Usually, the anti-noise signal is calculated by microphones integrated either on the outside or on the inside of the ear cups. Microphones on the outside directly pick up the noise generated by the engines and air flow over the plane, enabling a broadband noise reduction. Microphones fitted inside the headphones, on the other hand, pick up the sound signal close to the ear, and this sound can vary, above all depending on how well the headphones fit (different head shapes, wearing glasses, etc.). Internal microphones generally offer very good performance in the low-frequency range. NoiseGard™ / digital combines the benefits of both systems: the combination of external and internal microphones ensures a significantly better overall noise reduction, and thus more safety and comfort for the pilot.
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