01/06/2011 Wedemark

A whole new world at the touch of a button - Sennheiser´s NoiseGard technology

Roaring aircraft engines, rumbling trains – holidays and business trips are often linked with noisy and stressful journeys. Flying can be particularly tiring, as passengers on board a plane are often exposed to a continuous noise level of up to 80 dB. And on board of a train it can sometimes become loud as well. Senn-heiser's patented NoiseGard™ technology makes travelling as relaxed as possible by letting you enjoy music in peace. The innovative NoiseGard™ /digital system now offers travellers a choice of three noise-cancelling profiles – optimised for the different types of surrounding noise encountered while travelling.

Active noise cancellation: the idea is 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 cancelling out the unwanted noise. Sennheiser’s NoiseGard™ technology works as follows: miniature microphones integrated into the headphones pick up the low-frequency noise close to the ears. Sophisticated electronic circuitry 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 progressive development of Sennheiser’s analogue NoiseGard technology “, explained Daniel Chee, Product Manager for the Sennheiser Travel Line. The noise signals are picked up by analogue microphones in the headphones and converted into a digital signal, which is then processed by various software filters. The advantage: digital filtering not only ensures much more precise adaptation to interference, it also enables much more complex processing of the signal to be carried out. This makes additional functions available, such as the definition of different NoiseGard profiles.

The new CXC 700 with NoiseGard /digital has a total of three different modes to choose from to enable the noise-cancelling performance to be manually adapted to the current noise situation:

Mode 1 absorbs low-frequency noise in particular (100 to 400 Hertz), such as engine noise from trains, buses or small passenger aircraft. This NoiseGard profile is also effective in cancelling out wind noise.

Mode 2 focuses on cancelling noise in the medium frequency range (400 to 3,000 Hertz), which is caused above all by air-conditioning systems in large passenger aircraft or office buildings.

Mode 3 has a particularly wide frequency range (100 to 3,000 Hertz), and combines the noise-cancelling effect in the medium and low-frequency ranges. As a result, background noise with different noise components, such as that which occurs at airports, railway stations or underground stations, can be effectively suppressed, although with a slightly lower noise-cancelling performance than in the first two modes.

Passive noise attenuation
Active noise reduction – no matter whether it is analogue or digital – is supported by passive attenuation of ambient noise. Noise-attenuating materials and a closed design provide a particularly effective shield against high-frequency noise. The models in Sennheiser's Travel Line range from large, circumaural designs and supra-aural ear cups that fit snugly over the ears to models that fit perfectly in the ear canal. Active and passive noise attenuation work together to ensure that the noise level is optimally reduced both in high and low frequencies – ensuring that you arrive at your destination relaxed.

NoiseGard development over the years
Sennheiser initially developed the first headphones with the NoiseGard function for Lufthansa pilots. Today, the technology is used not only in professional pilots’ headsets at major airlines and in countless cockpits of private aircraft but also in headphones and headsets of Sennheiser's Travel Line. “We are well aware of the stresses that travellers are exposed to when flying,” said Daniel Chee, Product Manager for the Sennheiser Travel Line. “Since 1987, Sennheiser has been producing special headphones for pilots in order to protect them against noise and stress in the cockpit. The technology has been progessively developed and improved over the years“.

Lufthansa asks Sennheiser to develop noise-cancelling headsets for pilots. The technical challenge: although closed headphones offer good at-tenuation of high-frequency noise, they are ineffective against particularly annoying low-frequency noise (engine roar, wind noise).

Sennheiser engineers put Paul Lueg’s idea of ‘anti-noise’ into practice and launch the LHM 45 headset. It is the world's first pilot’s headset with active noise cancellation to receive FAA-TSO certification (Technical Standard Order of the Federal Aviation Administration).

Sennheiser launches the HDC 451 NoiseGard mobile, the first consumer headphones with active noise compensation. These passenger head-phones had previously been available only in the industrial range for air-lines.

The collapsible PXC 250 is launched, marking the breakthrough of NoiseGard technology in the consumer sector.

Launch of the PXC 150 and PXC 300 models. The latter uses the new NoiseGard Advanced system, which is less sensitive to external broad-band interference (mobile phones).

The PXC 350 and PXC 450, two large circumaural models, are presented. The PXC 450 is the first headphones to use NoiseGard 2.0 with optimised filters, microphones and processors for improved active noise reduction.

The PXC 310 BT is the first wireless travel headphones model. It com-bines NoiseGard technology with Bluetooth transmission. A further new feature is the combination with a hands-free system: the MM 450 TRAVEL Bluetooth headset with a NoiseGard function is presented. The head-phones model is also available as a wired version under the name PXC 310.

NoiseGard 2.0, Bluetooth 2.1 and SRS Wow HD SurroundSound. The PXC 360 BT travel headphones and the MM 550 TRAVEL headsets com-bine all three technologies for the ultimate in sound quality when travelling.

Sennheiser launches the CXC 700, the first headphones to feature NoiseGard /digital. The high-end ear-canal phones offer a choice of three NoiseGard profiles that can be selected according to the surrounding situation to achieve optimum noise reduction.

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