How the noise-canceling headphones would work if you're wearing a pair of headphones on a long airplane flight.
There are two sounds of interest to you, whatever it is you're trying to listen to and the tiresome drone of the engines.
The sound of the engines is coming from outside the headphones, the genius of noise-canceling headphones is that they can get rid of the sound of the engines without interfering with the so-called music.
All sound is just compression and rarefaction of the air around us.
When you fire a starting pistol, the air around the gun is compressed, then it thins out again, then it's compressed again and so on.
Imagine an infinite number of slinky stretching away in all directions and the sound rippling along with them. These are known as longitudinal waves, but for the purpose of illustration, we can represent them with sine waves with peaks and troughs like ripples in a pond.
The engines of the aircraft produce a sound wave of constant amplitude that is the height of the peak and the depths of the troughs and continuous wavelength that is the length of the entire wave.
And if you produce another sound with the same amplitude and wavelength but an opposite phase that is it has a peak where the original sound has a trough, you have something called an anti-phase.
The two cancel each other out, and the result is silence. Weirdly you add two things together but arrive at nothing but think of it as adding plus 2 to minus 2.
So noise-canceling headphones incorporate a tiny microphone that listens to the ambient noise, in this case, the jet engines, their internal electronics then measure this and work out an anti-phase, but of course, you don't hear the anti-phase you hear nothing. Because these microphones aren't listening to the sounds inside the headphones, your music is unaffected.
Noise-canceling headphones are much better at dealing with continuous noise like jet engines than they are at coping with sudden or abrupt sounds, so they don't work very well in a gunfight or else.
When you switch your noise-canceling headphones on, you'll notice a very short delay before they take effect. This is the electronics measuring the ambient sound, and coming up with the ante phase, they can't do it immediately.
Headphones like this were first devised in the 1970s, but by then, the technology was already well understood. Noise-canceling systems had already been incorporated in the cockpits of aircraft and helicopters.
More recently, it's become popular with carmakers not only can active noise cancellation make a car quieter by playing an anti-phase through the stereo speakers; it can actually improve the sound.
A sophisticated system can replace engine noise with something nicer so you can drive around in a dreary four-cylinder diesel hatchback but enjoy the soundtrack from a v12 Ferrari racing car.
This sort of thing is expensive, but then again, a Ferrari 250 GTO recently sold for 35 million dollars. Read More...
There are two sounds of interest to you, whatever it is you're trying to listen to and the tiresome drone of the engines.
The sound of the engines is coming from outside the headphones, the genius of noise-canceling headphones is that they can get rid of the sound of the engines without interfering with the so-called music.
All sound is just compression and rarefaction of the air around us.
When you fire a starting pistol, the air around the gun is compressed, then it thins out again, then it's compressed again and so on.
Imagine an infinite number of slinky stretching away in all directions and the sound rippling along with them. These are known as longitudinal waves, but for the purpose of illustration, we can represent them with sine waves with peaks and troughs like ripples in a pond.
The engines of the aircraft produce a sound wave of constant amplitude that is the height of the peak and the depths of the troughs and continuous wavelength that is the length of the entire wave.
And if you produce another sound with the same amplitude and wavelength but an opposite phase that is it has a peak where the original sound has a trough, you have something called an anti-phase.
The two cancel each other out, and the result is silence. Weirdly you add two things together but arrive at nothing but think of it as adding plus 2 to minus 2.
So noise-canceling headphones incorporate a tiny microphone that listens to the ambient noise, in this case, the jet engines, their internal electronics then measure this and work out an anti-phase, but of course, you don't hear the anti-phase you hear nothing. Because these microphones aren't listening to the sounds inside the headphones, your music is unaffected.
Noise-canceling headphones are much better at dealing with continuous noise like jet engines than they are at coping with sudden or abrupt sounds, so they don't work very well in a gunfight or else.
When you switch your noise-canceling headphones on, you'll notice a very short delay before they take effect. This is the electronics measuring the ambient sound, and coming up with the ante phase, they can't do it immediately.
Headphones like this were first devised in the 1970s, but by then, the technology was already well understood. Noise-canceling systems had already been incorporated in the cockpits of aircraft and helicopters.
More recently, it's become popular with carmakers not only can active noise cancellation make a car quieter by playing an anti-phase through the stereo speakers; it can actually improve the sound.
A sophisticated system can replace engine noise with something nicer so you can drive around in a dreary four-cylinder diesel hatchback but enjoy the soundtrack from a v12 Ferrari racing car.
This sort of thing is expensive, but then again, a Ferrari 250 GTO recently sold for 35 million dollars. Read More...
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