07/25/2011 Oshkosh

Sennheiser´s NoiseGard™ active noise reduction

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.

Passive noise attenuation

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.

The principle of active noise reduction

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

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.

30 years in aviation


Audio specialist Sennheiser launches its first aviation headsets, designed for the pilots of Lufthansa. The LHM 1410 / HME 1410 feature outstanding sound quality, solid reliability and optimum wearing comfort, which soon makes them a firm favorite with more than 100 airlines across the world.


Lufthansa asks Sennheiser to develop headsets with active noise reduction to protect pilots against low-frequency noise.


Sennheiser introduces the LHM 45 NoiseGard™, the world’s first pilot’s headset with active noise cancellation to receive FAA-TSO certification (Technical Standard Order of the Federal Aviation Administration).


The HMEC 200 is launched, Sennheiser’s first headset to combine active noise reduction with a closed ear defender design. An ideal headset for helicopters and propeller planes.


Sennheiser launches a true aviation classic, the HMEC 25.


Active and passive headsets are continuously optimized – and even make it into space: the cosmonauts of the Russian space station MIR use Sennheiser headsets.


The HMEC 460 is introduced. It features a separate module that houses two multi-media inputs – one for a cell phone and one for a music device. The module is powered by either two AA batteries or an XLR-3 connector and includes volume control, NoiseGard on/off switch, switch for boom left/right and a status LED.


The HMEC 250 is introduced, Sennheiser’s first aviation headset to use NoiseGard 2.0. Optimized filters, microphones and processors ensure an improved active noise reduction.


Sennheiser launches the S1 Digital, its first headset with NoiseGard™ / digital. The premium product features fully adaptive digital noise reduction, which can be continuously optimized for the current noise situation at the touch of a button.

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