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.
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.
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.
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.
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.
My macbook air also hums into my Bose earbuds. Disconnecting the magsafe power cable lessens it, but not by much. Touching the body of the computer dramatically decreases the hum (the more skin that touches, the greater the decrease).
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.
iMac 27 inch - late 2012, i7
Well, Apple probably won't like this advice but it EASILY worked for me :
I use the headphone jack output for audio playback from my iMac (Pro Tools, iTunes, etc) and after upgrading to the iMac from my Mac Pro (early 2008, quad core) physically configured the same way (headphone jack output to my speakers) the iMac would constantly emit a BUZZ shortly after any sound was outputted from it. i.e. : something like a system sound would play, there would be silence, and then after about 10 seconds or so the BUZZ would constantly output.
read and tried a few things that were completely useless and weird to even give a try (but I did regardless) - things like : 'zap the PRAM' ... reset the SMC ... switch to 32bit .... all weird, misguided and did not solve the problem.
I shut down the iMac, unplugged the power cable from the wall, grabbed a pair of needle nose pliers and then ripped off the GROUND PLUG from the power cable. Plugged it back in, booted back up and SOLVED. Apple's mention of a "ground loop" possibly being the problem in other posts was the best advice I found. They did/would not offer this solution but for me, after working in recording studios for more than 25 years now and experiencing MANY types of grounding issues with regard to BUZZ in the audio signal - it led me to just rip that ground plug off and move forward.
- As a professional I cannot profess to know that the possible negative implications might be from having a non-grounded iMac but let me just say that this is not the first time that I have done this with a computer or any type of gear for that matter to just basically "move on".
Let's see if Apple allows this post. Believe me - try it! If it doesn't help then make sure that you have a replacement IEC power cable (the one that has a female 3-pronged end and a male 3-pronged end) to swap out to if not successful.