7 ms·

visionOS thermally throttles based on how much it hears the fans in the mics

114 points by anonred 2y ago

ptsd_dalmatian 2y ago
Why use mics for that if they have direct access to rpm of fans?
- ketralnis 2y ago
  Maybe to give additional fans when the environment is so loud you can't hear them anyway
  - guerrilla 2y ago
    Sounds like a recipe for Heisenbugs.
    - jayd16 2y ago
      Somewhat, although I guess the idea is still to keep perf flat and just throttle the cooling.
    - userbinator 2y ago
      I can certainly see things like this causing a lot of unintended consequences. "It speeds up when I play loud music" is going to confuse many who don't know about this "feature".
      - mensetmanusman 2y ago
        “If you play the music loud, your fps will increase!”
  - bragr 2y ago
    Makes sense. Humans are really bad at perceiving the environmental noise floor. Our brains just tune it out, but it is has a huge impact on your perception of the loudness of fans that you've strapped to your face.
- tommiegannert 2y ago
  I can't speak for Apple, but for my Prusa 3D-printer: Worn/cheap ball bearings will make a rattling sound until they heat up and the balls expand. If you care about the auditory experience, using audio in the feedback loop makes some sense.
- makeitdouble 2y ago
  The goal is probably not to absolutely manage cooling but to focus on the audio experience and try to keep noise below some threshold. I think that's an interesting idea, even if not everyone might be happy with the tradeoff (comes down to how much you care about noise vs getting throttled), especially for a vr device.
  - jfoster 2y ago
    It seems a mis-prioritization of the kind that makes me dislike Apple products. To avoid the imperfection of a bit of fan noise, throttle the entire experience. Great.
    - freehorse 2y ago
      It is a machine you literally have on your head. I have not tried it, but I can believe that it requires some different UX considerations than normal computers. I would definitely not like to hear fan noise vibrating through my head.
      - Guillaume86 2y ago
        Wait till you experience visual stutter in VR then...
        andybak 2y ago
        In the old days, the device settings would allow the user to tune the trade-off to their own preferences. But current user design orthodoxy is that "settings are bad" to an extreme (I actually agree with the weaker formulation "too many settings are bad"... for some value of "many")
        klausa 2y ago
        There's a reason why the Vision Pro has separate chip that handles the real-time passthrough from cameras (and bunch of other sensor-fusion stuff, AIUI).
- hyperhopper 2y ago
  The thread explains one possible reason why. You should read the link before commenting. The reason proposed is that if the environment is loud, you won't be bothered by additional noise from the fans.
  - theon144 2y ago
    The post you're probably talking about was hidden under "Show Probable Spam" on my end.
  - latexr 2y ago
    > You should read the link before commenting. Twitter doesn’t show threads to people who are not logged in (e.g. if you don’t have an account). Shaming people for not reading what they can’t see (or even know exists) is unfair. Using archival sites doesn’t work as a bypass like on newspaper sites. Not to mention people on Firefox, which from what I have read on HN might not even have access to it at all. Twitter links should probably be downranked on HN until (if/when) they return to being more accessible.
    - andybak 2y ago
      I had no idea Twitter was doing that. That sucks. However - I find that less onerous than a paywall and HN is mostly fine about those.
      - latexr 2y ago
        > I find that less onerous than a paywal With a paywall you know what you’re missing or not. With Twitter that’s harder to determine, which I’d argue is worse. But I wouldn’t say either of our opinions is objectively correct. > and HN is mostly fine about those. It is explicitely fine with paywalls which have workarounds. https://news.ycombinator.com/newsfaq.html https://news.ycombinator.com/newsfaq.html
- whyoh 2y ago
  Because the RPM of a fan is not a 100% reliable indicator of its loudness. Sometimes a lower speed can even be louder than a higher one, because of certain resonances...
  - FireBeyond 2y ago
    Presumably, knowing the fan you've installed into the device you've designed, you could map those noisy areas...
    - whyoh 2y ago
      Yes, that could work (it would need to be done for each fan individually, because of manufacturing variation). But it's still not guaranteed that the fan will keep working the same way in the future, after some use/deterioration or in untested conditions.
rickdeckard 2y ago
Quite smart idea, not for throttling when the fans are heard, but SPEEDING THEM UP while they are NOT heard, based on the noise floor of the current environment. This, combined with an assessment how much of the environment the user currently hears (i.e. maybe he is watching a movie), could provide a lot of headroom for additional cooling without bothering the user.
- jayd16 2y ago
  If your face gets hot, turn on the radio.
dvh 2y ago
Another trick is not to use constant RPM because you can hit some mechanical resonance point, but constantly varying RPM around target RPM so that the system even if it hits resonance stays there only for a brief moment and won't start vibrating.
- thebruce87m 2y ago
  They do the same with clock signals in some systems. Similar idea to avoid high peaks at a single frequency: > Spread spectrum clocking is a technique used in electronics design to intentionally modulate the ideal position of the clock edge such that the resulting signal’s spectrum is “spread”, around the ideal frequency of the clock. In timing circuits, this has the advantage of reducing Electromagnetic Interference (EMI) associated with the fundamental frequency of the signal. https://www.microsemi.com/document-portal/doc_view/135439-white-paper-spread-spectrum-clocking https://www.microsemi.com/document-portal/doc_view/135439-wh...
  - immibis 2y ago
    This is controversial, because the same amount of noise is emitted, just with a different shape that is still able to be picked up by radio receivers just as well, but is more likely to pass regulatory tests.
    - mlyle 2y ago
      We have a standard for the maximum energy on given frequencies, not the total EM emitted. Spread spectrum clocking definitely reduces the peak energy on specific frequencies, which is usually what you care about more. I guess it makes you more likely to experience interference, but the interference you'll experience, on average, will be much less severe.
      - immibis 2y ago
        No radio receives exactly a single frequency. They all receive a range.
dayjaby 2y ago
Isnt something similar possible for cars? Based on certain frequencies in the motor area, you can deduce what is faulty?
- hoerensagen 2y ago
  That is definitely done for bearing in ratting machinery. You can often even pinpoint which bearing is damaged and which part of that bearing is damaged, based on the frequency spectrum.
- janice1999 2y ago
  There are several companies that use vibration and sound to detect faults (condition based monitoring). Otosense was one (now part of Analog Devices). https://www.analog.com/en/lp/001/machine-health-sensing.html https://www.analog.com/en/lp/001/machine-health-sensing.html
raverbashing 2y ago
For those who are confused: the title is a bit misleading, it's actually the other way people might expect (if you read the thread) Noisy environment: turn the fans all the way as the user -> more cooling -> processor doesn't throttle Quiet environment: turn the fans down -> processor throttles
- deely3 2y ago
  Oh, that makes sense. As well as a fact that screaming on a pc will make it work quicker.
- jayd16 2y ago
  For VR perf its probably a bad idea to throttle the performance. A better goal would be to balance user comfort. You can trade noise for thermal comfort.
rmccue 2y ago
macOS does this too; if you trigger Siri while your fans are spun up, it’ll temporarily spin them down to hear you more clearly.
jdlyga 2y ago
"Bug Report: My framerate significantly drops in Microsoft Flight Simulator for Vision OS but only when not using headphones"
andihow 2y ago
[dead]

114 points by anonred 2y ago

ptsd_dalmatian 2y ago

Why use mics for that if they have direct access to rpm of fans?

ketralnis 2y ago
Maybe to give additional fans when the environment is so loud you can't hear them anyway
- guerrilla 2y ago
  Sounds like a recipe for Heisenbugs.
  - jayd16 2y ago
    Somewhat, although I guess the idea is still to keep perf flat and just throttle the cooling.
  - userbinator 2y ago
    I can certainly see things like this causing a lot of unintended consequences. "It speeds up when I play loud music" is going to confuse many who don't know about this "feature".
    - mensetmanusman 2y ago
      “If you play the music loud, your fps will increase!”
- bragr 2y ago
  Makes sense. Humans are really bad at perceiving the environmental noise floor. Our brains just tune it out, but it is has a huge impact on your perception of the loudness of fans that you've strapped to your face.
tommiegannert 2y ago
I can't speak for Apple, but for my Prusa 3D-printer: Worn/cheap ball bearings will make a rattling sound until they heat up and the balls expand. If you care about the auditory experience, using audio in the feedback loop makes some sense.
makeitdouble 2y ago
The goal is probably not to absolutely manage cooling but to focus on the audio experience and try to keep noise below some threshold. I think that's an interesting idea, even if not everyone might be happy with the tradeoff (comes down to how much you care about noise vs getting throttled), especially for a vr device.
- jfoster 2y ago
  It seems a mis-prioritization of the kind that makes me dislike Apple products. To avoid the imperfection of a bit of fan noise, throttle the entire experience. Great.
  - freehorse 2y ago
    It is a machine you literally have on your head. I have not tried it, but I can believe that it requires some different UX considerations than normal computers. I would definitely not like to hear fan noise vibrating through my head.
    - Guillaume86 2y ago
      Wait till you experience visual stutter in VR then...
      - andybak 2y ago
        In the old days, the device settings would allow the user to tune the trade-off to their own preferences. But current user design orthodoxy is that "settings are bad" to an extreme (I actually agree with the weaker formulation "too many settings are bad"... for some value of "many")
      - klausa 2y ago
        There's a reason why the Vision Pro has separate chip that handles the real-time passthrough from cameras (and bunch of other sensor-fusion stuff, AIUI).
hyperhopper 2y ago
The thread explains one possible reason why. You should read the link before commenting. The reason proposed is that if the environment is loud, you won't be bothered by additional noise from the fans.
- theon144 2y ago
  The post you're probably talking about was hidden under "Show Probable Spam" on my end.
- latexr 2y ago
  > You should read the link before commenting. Twitter doesn’t show threads to people who are not logged in (e.g. if you don’t have an account). Shaming people for not reading what they can’t see (or even know exists) is unfair. Using archival sites doesn’t work as a bypass like on newspaper sites. Not to mention people on Firefox, which from what I have read on HN might not even have access to it at all. Twitter links should probably be downranked on HN until (if/when) they return to being more accessible.
  - andybak 2y ago
    I had no idea Twitter was doing that. That sucks. However - I find that less onerous than a paywall and HN is mostly fine about those.
    - latexr 2y ago
      > I find that less onerous than a paywal With a paywall you know what you’re missing or not. With Twitter that’s harder to determine, which I’d argue is worse. But I wouldn’t say either of our opinions is objectively correct. > and HN is mostly fine about those. It is explicitely fine with paywalls which have workarounds. https://news.ycombinator.com/newsfaq.html https://news.ycombinator.com/newsfaq.html
whyoh 2y ago
Because the RPM of a fan is not a 100% reliable indicator of its loudness. Sometimes a lower speed can even be louder than a higher one, because of certain resonances...
- FireBeyond 2y ago
  Presumably, knowing the fan you've installed into the device you've designed, you could map those noisy areas...
  - whyoh 2y ago
    Yes, that could work (it would need to be done for each fan individually, because of manufacturing variation). But it's still not guaranteed that the fan will keep working the same way in the future, after some use/deterioration or in untested conditions.

rickdeckard 2y ago

Quite smart idea, not for throttling when the fans are heard, but SPEEDING THEM UP while they are NOT heard, based on the noise floor of the current environment. This, combined with an assessment how much of the environment the user currently hears (i.e. maybe he is watching a movie), could provide a lot of headroom for additional cooling without bothering the user.

jayd16 2y ago
If your face gets hot, turn on the radio.

dvh 2y ago

Another trick is not to use constant RPM because you can hit some mechanical resonance point, but constantly varying RPM around target RPM so that the system even if it hits resonance stays there only for a brief moment and won't start vibrating.

thebruce87m 2y ago
They do the same with clock signals in some systems. Similar idea to avoid high peaks at a single frequency: > Spread spectrum clocking is a technique used in electronics design to intentionally modulate the ideal position of the clock edge such that the resulting signal’s spectrum is “spread”, around the ideal frequency of the clock. In timing circuits, this has the advantage of reducing Electromagnetic Interference (EMI) associated with the fundamental frequency of the signal. https://www.microsemi.com/document-portal/doc_view/135439-white-paper-spread-spectrum-clocking https://www.microsemi.com/document-portal/doc_view/135439-wh...
- immibis 2y ago
  This is controversial, because the same amount of noise is emitted, just with a different shape that is still able to be picked up by radio receivers just as well, but is more likely to pass regulatory tests.
  - mlyle 2y ago
    We have a standard for the maximum energy on given frequencies, not the total EM emitted. Spread spectrum clocking definitely reduces the peak energy on specific frequencies, which is usually what you care about more. I guess it makes you more likely to experience interference, but the interference you'll experience, on average, will be much less severe.
    - immibis 2y ago
      No radio receives exactly a single frequency. They all receive a range.

dayjaby 2y ago

Isnt something similar possible for cars? Based on certain frequencies in the motor area, you can deduce what is faulty?

hoerensagen 2y ago
That is definitely done for bearing in ratting machinery. You can often even pinpoint which bearing is damaged and which part of that bearing is damaged, based on the frequency spectrum.
janice1999 2y ago
There are several companies that use vibration and sound to detect faults (condition based monitoring). Otosense was one (now part of Analog Devices). https://www.analog.com/en/lp/001/machine-health-sensing.html https://www.analog.com/en/lp/001/machine-health-sensing.html

raverbashing 2y ago

For those who are confused: the title is a bit misleading, it's actually the other way people might expect (if you read the thread) Noisy environment: turn the fans all the way as the user -> more cooling -> processor doesn't throttle Quiet environment: turn the fans down -> processor throttles

deely3 2y ago
Oh, that makes sense. As well as a fact that screaming on a pc will make it work quicker.
jayd16 2y ago
For VR perf its probably a bad idea to throttle the performance. A better goal would be to balance user comfort. You can trade noise for thermal comfort.

rmccue 2y ago

macOS does this too; if you trigger Siri while your fans are spun up, it’ll temporarily spin them down to hear you more clearly.

jdlyga 2y ago

"Bug Report: My framerate significantly drops in Microsoft Flight Simulator for Vision OS but only when not using headphones"

andihow 2y ago

[dead]