26

I don't own noise-cancelling headphones, but I do own a macbook (which has a microphone) and a pair of headphones.

Is there a way for me to use this set-up (some macOS app or such) to cancel noise in the same way active noise-cancelling headphones do?

34

In short, no.

The measurement required to provide correct phase-cancellation in a headset is measured in microns, not inches.
You could neither measure it accurately enough nor stay still enough for it to work.
You would also suffer so much throughput latency in hard & software that any attempt at correction would arrive far too late to be of any use.

Some people seem to object to my definition of the precision required for this to be effective.
Let's add more to that.

Not only do you need your distances to be accurate for the gap between mic & speaker, but you also need to be feeding the resultant audio back at the correct phase with regard to the speaker/mic orientation.
If you are trying to do this using a mic oriented at approximately 90° to the headphone speakers, assuming you are facing the computer, your chances of success are even smaller.

You then need to decide which phase you are going to send to which ear. Are you going to guess at an approximation of the 90° & then flip one by 180° compared to the other?

Does that better explain why these systems are measured in microns, not inches? It has little to do with the wavelength at any given frequency & more to do with the orientation of your phase... otherwise you are just as likely to reinforce the wave as to cancel it.

  • 3
    Microns? Hah. A typical 5 kHz sound has a wavelength of around 7 cm or 3 inches. Phase doesn't need to be measured more accurately than a few degrees to get virtually complete cancellation, so only mm to cm placement accuracy is required. – Forrest Voight Jun 10 '17 at 6:32
  • If you think my exaggeration for emphasis makes the answer wrong, then downvote it. If you have a better answer, please supply it. In practical terms, it's the latency that will be insurmountable, rather than the phase-shift itself. – Tetsujin Jun 10 '17 at 6:55
  • 2
    How is one supposed to know that it is an exaggeration? Why are you so defensive? Ok, @ForrestVoight could have left out the “Hah”, but I do not think that this was so bad. – Carsten S Jun 10 '17 at 10:46
  • I added further explanation as to why the wavelength itself is unimportant. – Tetsujin Jun 10 '17 at 11:00
  • 3
    This answer can be summed up by asking the question: How many noise cancellation systems are available for rooms? None. This answer explains why. – Allan Jun 10 '17 at 11:45
15

I guess that won't work for the simple reason that the lag between microphone and headphones is simply too long to cancel a noise before you hear it.

If you use google translate, this article explains the issues in a bit more detail : https://www.heise.de/ct/hotline/PC-Beruhigung-mit-Antischall-319834.html

What kind of works is cancelling a constant noise through a normal headset by calculating and then manually adjusting the phase of the Gegenschall.

9

As much as they would like you to believe it Apple is not capable of violating the laws of physics.

Noise cancellation works because the relative positions between the speaker, ear and microphone are precisely known. When you have cord between your headphones and microphone (laptop) you no longer know the relative positions.

Mac OS is not a real time operating system, it is unlikely that it could do it even if you could bolt your head to your laptop.

  • But the poster said it was Magical! ;) – StockB Jun 8 '17 at 18:40
  • 1
    You could theoretically find out the relative positions by doing phase difference measurements, calibrating via a known-phase tone from the headphones/speaker... :) – rackandboneman Jun 8 '17 at 20:28
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    @rackandboneman - would do nothing for the latency, though. – Tetsujin Jun 8 '17 at 20:56

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