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Comment by TillE | Hacker News Reader

I was a little surprised to see not one but two huge fans. Reviewers have mentioned hearing no fan noise, but maybe they crank up a little if you really push the GPU + CPU with a 3D game.

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Someone managed to get a mention of them out of someone at Apple a while ago.

Not only are they quiet, but the EarPods (built in headphones) do active noise cancellation against them for the person wearing the Vision Pro.

I don't think it is possible to do open air noise cancelation like that. Do you remember where you saw that mentioned?

Why not? There are active noise cancellation systems for airplanes and cars where the distance between the speaker and the ear is much greater than in this case.

As I understand it, niose cancelation requires an enclosed volume of space. It's why you never see it on open back headphones. Cars and aeroplanes are completely enclosed too.

Active noise cancellation is just destructive interference. It doesn't fundamentally require any sounds to be bouncing off surfaces, and mechanical isolation would be passive noise cancellation.

The main caveat to active noise cancellation is that you cannot construct a destructive interference pattern that cancels the noise everywhere. Creating destructive interference to cancel out the noise at your ears will unavoidably mean creating constructive interference somewhere else.

see galaxy buds live, the only limitation is that active noise cancellation works up to certain frequency when passive cancellation must take over

I think they have a lot of advantages here. They have tons of microphones, they know exactly what the noise sounds like, exactly where it is positioned and exactly where the speakers are relative to your ears.

I suspect that makes the problem constrained enough that it becomes possible.

its possible, but expensive.

Every Honda, even the cheap ones, do active noise cancelling in a whole car cabin. It’s definitely possible.

Any PC builder can tell you that the bigger and more fans you get the quieter and slower rpm they can run

But also more weight

Probably precisely why they use two fans. Have them really silently instead of one audibly.

Also probably why they are relatively big for a device of this size.

If you're designing for a specific airflow target, making the fans larger lets you make them quieter because they can spin slower than smaller fans while displacing the same amount of air.

That and there are two major chips, the R1 and M2, acting as distinct heat sources. I don't know if they would spin the fans up and down independently, but the two chips' heat output could differ over time.

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