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Switched recently from a Lenovo PC and one thing on my mac bothered me. Headphones plugged into my Macbook pro 13" (latest version) "hum" with static when there is no audio playing. Then after a short period of time, they stop humming, as if all power to the port is turned off. When any sound plays, it starts again. Anybody know of any setting in the Mac "bios" (or whatever they call it) or with drivers or software to get it to stop humming? It's rather annoying.

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This "hum" you speak of happens on my iPad and I've just gotten used to it. It's not noticeable when sounds are playing. – user479 Feb 9 '11 at 6:51
Does the humming change or stop when you unplug everything else, including the magsafe power cable? Does it change when you play with the screen brightness? Does it change when the Mac is first turned on and still cold to the touch? – hotpaw2 Feb 9 '11 at 9:12
I've only noticed noise using apple ear buds, if I use any other set of headphones I don't hear humming of any sort. – Dustin Dec 1 '11 at 19:10
I can confirm that removing the MagSafe cable solves the problem. Still, I'm looking for a permanent solution that would allow me to power the mac :) – sorin Feb 6 '12 at 17:06

I found the solution to my problem. For some reason (who knows why) the headphone output was set to 16-bit. Of course that's going to sound awful.

To fix this, head to 'Audio MIDI Setup' (can be found with Spotlight) and change the 'Built-in Output' to 32-bits.

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Audio MIDI Setup can be found in the Utilities (Command-Shift-U, from the Finder, or Utilities folder inside the Applications folder). Thanks: this did solve my (light) humming problem. – EOL Jun 20 '15 at 23:49

What you are hearing is the intrinsic noise of the Macbook's DAC and output buffers.

The output does actually power down when it goes unused for a certain period of time, which is why the noise goes away. The analog output is powered down to save battery.

Unfortunately, since the noise is intrinsic to the system, the only way to disable it is to completely disable the ability to output any sound.

There may be a way to modify the period of time it takes before the output gets powered down, but I am not familiar with any.

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… or you could try using an external (e.g. USB-powered) DAC that has a lower noise, but thats quite a lot trial & error. – Asmus Feb 9 '11 at 11:34
"Step 1:Plug it in, Step 2:Install Drivers".... That's a lot of trial and error? – Fake Name Feb 10 '11 at 11:15

Closing my web browser solved my buzz problem!

My Mac Pro started an electronic type of buzzing sound suddenly in the past few weeks.

The sound was coming from the audio output (headphone jack or firewire audio output - same issue)

I had incorporated some new speakers recently and I thought maybe it was some kind of new grounding problem. While attempting to pursue a solution to the problem, on a whim I decided to shut down my mac to see if that might do anything.

While preparing to shut down I was closing various programs. Then I closed down Google Chrome, on which I had about 10-15 tabs open... and the sound went away!

I've never experienced something like this before. I'm imagining perhaps it was some kind of issue with one of the pages I had up.

I've often had multiple browsers windows, each with multiple tabs open and never had this kind of thing happen... so this was unique experience for me.

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Had the same problem, closed everything and the sound card went back to normal. – aljndrrr Dec 22 '14 at 20:29

The hum is also present for me, even with unplugging everything. Actually, if you have a look (or at least, for me, this is the case) if you touch the body of the machine, it ceases to hum. It must be some kind of static buildup of charge on the aluminium body, and when you touch it, your body acts as a very large condenser.

When you can ground the machine with your body, you might want to check the power cord and replace an ungrounded "duck head" or cord with one that goes to a properly grounded wall receptacle. Also, take a toothbrush to the magsafe connectors to ensure all the springs work and make contact to the connector on the mac.

If you use an external USB I/O (I use a mixer, for I'm a session musician), the hum is not plagueing the alternative sound source.

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Bmike above said that when he touched his, it got rid of the problem. if it's true for you as well OP, try touching the base and a brick wall or something, or lick your fingers and wipe the bottom with them a little. for any other solutions look up how to get rid of static electricity on google.

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