The constantly chattering passenger on the train, 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 noise? Aren’t there also disadvantages?
Theory
Sound is transmitted in the form of waves, such a wave consists of mountains and valleys. The trick to reducing noise, in technical jargon active noise canceling (ANC) is to match every mountain with a valley and every valley with a mountain. A speaker cone that wants to move forward and thus set the air vibrating is simultaneously commanded to move backwards. This works because microphones capture the sound and electronics calculate what the counter-sound must look like. Result: The loudspeaker membrane does not move (almost) at all. That’s the theory.
The practice
In practice, there is always a remnant of the prevailing noise. The more uniform and deeper the noise and the better the technology used, the lower this remainder is. Deeper, uniform noises such as the hissing and humming on airplanes or the noise of driving on the train can be reduced to a faint hissing. Short, impulsive, higher-frequency noises cannot be filtered out as well. Voices, for example, can be heard despite noise canceling. How strong depends on how well the technology has been implemented. Usually this has to do with the price. Electronics that work more precisely and faster are also more complex and therefore more expensive.
What does ANC do with the sound?
In order for the noise cancellation 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 distinguish between what is filtered out and what remains. With some models you can therefore hear a clear difference in the sound when you switch ANC on and off. It is not possible to give a general answer to what extent the electronics interfere with the sound. It is best to try different types of headphones with the music that you want to hear with them.
Inevitable noise
For technical reasons, ANC headphones also produce their own noise. With the better devices, however, this is hardly noticeable. Of course, it also depends on the music you listen to with it. With classical music, where it can sometimes get very quiet, the inherent noise is more annoying than with pop music, which is usually optimized for the greatest possible volume.
Nothing works without electricity
In order to operate the electronics, ANC headphones need electricity. They usually get it from lithium-ion batteries. However, most headphones can withstand a long-haul flight – if you haven’t forgotten to charge them beforehand.
radio or cable?
Of course, purists turn away in horror, but the trend is still towards wireless headphones. The Bluetooth standard has prevailed here. The highest quality variant of this automatically uses the best available method for transmission. Headphones and playback device coordinate with each other. Hifi aficionados are not so enthusiastic about Bluetooth because the music data has to be compressed during transmission. This causes so-called artefacts, i.e. sounds that were not actually present in the music. This can be, for example, hissing cymbals or an acoustic shimmering, for example when a piano is played. Many ANC headphones can also be used with a cable. This is also an advantage because in some aircraft it is forbidden to use wireless headphones for safety reasons.
Open or closed?
The question arises only in the case of non-noise-cancelling headphones. Headphones with ANC always have a closed design, so they 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 as well as possible with silicone caps, which are available in different sizes. The luxury variant: You can have hearing aid acousticians make adapters that are adapted to your individual ear, into which the earphones are then inserted.
