How do Noise Cancelling headphones work?
This is how the noise cancelling headphones –θήκες κινητών– work. Many companies have released this technology which allows you to get a break from the world and from whatever is going on around you! It is an investment that you would want to make if you are traveling very often, if you keep taking the train or the bus to wok, and generally if you need to be isolated and keep the background noises away from your ears.
These type of headphones, were mostly used as noise reducing headphones from musicians and singers when they were recording songs and music pieces. Now they have been used widely by pretty much everyone of us, as the wild rhythm of the everyday life has made us do so.
The annoying background noise in the aircraft can be almost completely suppressed with noise-reducing headphones. Noise-canceling headphones are very fashionable. But how do they actually work? And what does it depend on whether they sound good?
The background noises
The passenger on the train chatting away, the noise of the turbines on the plane or the hell in the open-plan office – there are enough reasons in favor of noise-reducing headphones. But does it really work to reduce the noise? Aren’t there disadvantages too?
Theory
Sound is transmitted in the form of waves, such a wave consists of mountains and valleys. The trick in noise reduction, known in the technical jargon as active noise canceling (ANC), is to oppose each mountain with a valley and each valley with a mountain. A loudspeaker membrane that wants to move forwards and thus set the air vibrating, receives the command to move backwards at the same time. This works because microphones pick up the sound and electronics calculate what the counter-sound should look like. Result: The speaker membrane (almost) does not move at all. So much for the theory.
The practice
In practice there is always a remnant of the prevailing noises. This remainder is less, the more uniform and deeper the noise and the better the technology used. Lower, uniform noises such as the hissing and humming noise in an airplane or the driving noise in the train can be reduced to a low level of noise. Short, impulse-like, higher-frequency noises can be filtered out less effectively. Voices, for example, can be heard despite noise canceling. How much depends on how well the technology has been implemented. As a rule, this has to do with the price. Electronics that work faster and more precisely are also more complex and therefore more expensive.
What does ANC do with the sound?
For the noise suppression to work, the electronics must intervene in the sound. This is not without consequences. After all, it is up to the algorithms used, which have to differentiate between what is filtered out and what remains. With some models you can therefore hear a clear difference in sound when you switch ANC on and off. There is no general answer to how far the electronics interfere with the sound. It is best to try different headphones of this type with the music that you want to hear with them.
Inevitable noise
For technical reasons, ANC headphones also produce inherent noise. This is hardly noticeable with the better devices. In addition, of course, it depends on the music you hear with it. With classical music, where it can sometimes get very quiet, the inherent noise is more disturbing than with pop music, which is usually optimized to the highest possible volume.
Nothing works without electricity
ANC headphones need electricity to operate the electronics. They usually get it from lithium-ion batteries. Most listeners can take a long-haul flight – if you haven’t forgotten to charge them beforehand.
Radio or cable?
Purists turn away with horror, of course, but the trend is still in the direction of wireless headphones. The Bluetooth standard has established itself here. The highest quality variant of this automatically uses the best available method for transmission. Headphones and playback device coordinate with each other. Hi-fi aficionados are not so enthusiastic about Bluetooth because the music data has to be compressed during transmission. This causes so-called artifacts, i.e. sounds that were actually not present in the music. These can be, for example, hissing cymbals or an acoustic whirring sound when you strike the piano. Many ANC headphones can also be used with cables. This is also an advantage because it is forbidden to use wireless headphones in some aircraft for safety reasons.
Open or closed?
The question only arises with headphones without noise cancellation. Headphones with ANC always have a closed design, i.e. they also seal the ear with their closed shell. It is similar with earphones, which are also available with ANC. These sit in the ear canal and close it off as best as possible with silicone caps, which are available in different sizes. The luxury variant: You can have adapters made to fit your individual ear by hearing aid acoustical, into which the earphones are then inserted.
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