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My old 2008 Macbook's iSight microphone is acting up but only under OSX. In bootcamp running Windows XP, it's fine!

The problem is a high pitched sound, very reminiscent of old radios with the pitch going up and down.

  • It happens regardless of the app I use
  • Rebooting OSX did not make a difference.
  • Adjusting the mic volume does not help.
  • Turning ambient noise reduction off does not help.
  • CPU is idle and fans at 3200rpms, same as Windows XP
  • I've not changed any audio settings or loaded any audio software
  • It's happening while using headphones so it's not a feedback loop

Windows XP does NOT have this high pitched noise, just the normal background noise and it is usable.

Any ideas?

PS: Not that I think it's relevant but I'm running Snow Leopard.

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It's quite old question but I had same problem with two USB cameras just few days ago. To fix it go to the MIDI setup (i.e. by Spotlight Search Bar). On the left side choose your USB microphone (USB camera) and on the right try to change frequency to 44 100Hz and format 16-bit. Previously I had 24-bit which causes the problem.

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The immediate cause of the noise is feedback from the speakers is being amplified by the microphone.

To get out of the loop mute the speakers or plug in headphones. Then go to the sound system preference pane and dial down the gain on the iSight camera microphone.

If you can't live with a gain level that is below the feedback loop, you may need to seek hardware repair. Before that, I'd install a clean OS onto an external USB drive and be sure you don't have any software issues or settings.

Depending on the cost of the repair, you can use an external microphone, use better care with the levels of input/output, use headphones when recording to avoid fixing the root cause if it's actually a hardware issue. That's an unlikely outcome as you've not reproduced it under windows - so focus on software first.

  • Sorry forgot to mention that I am using headphones so it is NOT feedback. I've updated my question to include that... – Vic Sep 24 '15 at 17:55
  • @Vic Bizarrely rare situation - that's more likely hardware then. If you power off the Mac, disconnect all connections including the headphone (basically use a keyboard when you must to log in, then disconnect it - leaving just a mouse) does it feed back? – bmike Sep 24 '15 at 18:23

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