Whining mini power supply during sleep

Question

Whining mini power supply during sleep

When my Mini is put to sleep, I can hear a very gentle whining high frequency noise from the power supply. Its waveing up and down in intensity and a bit in frequency as the LED on the front of the Mini dims in and out.

I don't think everyone will hear this sound since it is very light and hi-frequent. And most of you won't hear it without putting your ear to the power supply.
But this sound actually prevents me from sleeping! The power supply, and the rest of the set up is about 2 metres from my head when I'm lying in bed.
Is there anyone out there who can surely tell they dont have this problem, or "phenomenon"? Or is there anyone who knows about a solution to my problem? I have a drawer nearby which i've thougt about putting the PS in with som clothing to dampen the sound, but I'm afraid it will get too hot. Please help me with this my biggest life issue!

Regards
Johan Wahlberg

Posted on Nov 7, 2005 5:59 PM

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Answer 1

AndyO

Level 6

17,064 points

Nov 8, 2005 7:12 AM in response to Johan Wahlberg

28.4 seems a bit high to me - not critically so, since the system as a whole is rated for use up to 35, but it's certainly approaching the point at which it's reasonable to expect longer-term reliability to be affected.

I would suggest you continue to monitor temperature, and either improve ventilation or move the power supply out of the drawer again if the temperature continues to rise.

The operating temperature range of the mini (and all the other details) are at http://www.apple.com/macmini/specs.html

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Answer 2

Nov 7, 2005 9:50 PM in response to Johan Wahlberg

Concidently, I have my mini setup on my bedstand (Not a lot of options in a two room appartment.

I have been running my mini 24/7 but it has not distrubed my sleep at all. Don't know if this means yours is loud or it just doesn't bother me.
I could and have slept next to my powerwave as well.

I would just setup the mini somewhere else if possible or shut it down.
I seem to recall the mini is not supposed to have anything placed on top of it.

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Answer 3

Nov 8, 2005 3:29 AM in response to Rotten Apple1

I think you just never heard it. I don't believe this to be a manufactur problem, it is just a problem for me.
But since I could just shut it down insted of putting it to sleep, I have a simple solution to the problem. I mostly want to share my thoughts...

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Answer 4

Nov 8, 2005 6:09 AM in response to Johan Wahlberg

Johan-

I am curious. Can you also hear the whine of a high voltage power supply within a CRT based monitor?

Many people with normal hearing cannot detect that whine. I suspect that you can. I can hear the whine of a crt. I do not hear any noise coming from my brick on the mini.

-DaddyP

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Answer 5

Nov 8, 2005 6:28 AM in response to DaddyPaycheck

I suppose you are talking about the ultra high frequency whine of any crt monitor or tv. ~20.000Hz
Yes, I can hear that sound. I recall days when I was younger I could hear if the TV was on down in the livingroom from upstairs! Now I have to be in the same room. Crt monitors are a bit quiter i think, but I can hear them if i concentrate on the sound. You usually don't notice this sound by old "habit".
I can also hear a humming sound from most ac adapters used at home, but not farther away than say, 0.2~0.7 metres at maximum, and then only in a totaly silent room. Unless I put my ear to the device. So is also with the brick of the mini, exept for this hifreq noise when its put asleep, which is lower in both frequency and intensity than a crt monitor.

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Answer 6

AndyO

Level 6

17,064 points

Nov 8, 2005 6:31 AM in response to Johan Wahlberg

Different people hear over different frequency ranges and with than range, have different sensitivities to different frequencies - which means that even if all Mac mini power supplies make this noise, not all people would be likely to hear it, and of those who can, not all would notice it, even if the environment in which the mini is located is sufficiently quiet that the sound would be audible at all.

Where a solid-state device like the mini's PSU does make this sort of noise, it's often caused by resonance in components, and would typically be at high frequency. The higher the frequency, the shorter the wavelength, which means that you may find you can completely eradicate the noise by doing little more than moving the power supply around. At the low end of human hearing (around 20Hz) you might have to move the audio source as much as 40 feet to make any difference in perceieved volume level, but at the top end of human hearing (typically 20KHz) it's more likely to be a few inches.

ON EDIT: I should also add that the higher the frequency, the easier it typically is to damp out or block.

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Answer 7

Nov 8, 2005 6:44 AM in response to AndyO

I have now put the brick down in a drawer of the little stand the mini is on top of, its an old nightstand table. The drawer is about 300x200x200 mm and has an air vent in the back.
I cant hear the sound anymore.
But I am monitoring the temp inside the drawer. In 1h 45min the temp went up from 23.5 to 28.4 C. How high temp do you think is safe without having the brick damaged or a degrade in quality or stability of power to the mini? I have searched apple support for info on working temperature etc with no results...

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Answer 8

Nov 8, 2005 7:22 AM in response to Johan Wahlberg

Johan-

I have worked trouble shooting CRT monitors for 25 years. As I seem to have the same sensitivity to sound in your range, my colleagues were always amazed that I could troubleshoot a malfunctioning HV supply with my ears.

The sound does bug the bejeezus out of me if I let it.

As long as your drawer temperature stays under the rated system limit then you should be OK. I have always been able to deflect and minimize the sound by simply placing a solid object between me and the offending source and/or change the orientation of the source to try and bounce the offending frequency away.

I suspect that you being able to hear the frequency pitch change of the power supply is akin to changing a CRT power supply "whine" by changing it's brightness. It takes higher frequency for whatever period of time it takes to produce the juice needed to brighten the bulb.

Peace-

DaddyP

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Answer 9

Pos

Level 4

1,170 points

Nov 8, 2005 3:50 PM in response to Johan Wahlberg

Hi Johan,

I also hear this high pitched up and down screaming noise that the mac minis power brick emits. I made a topic about it several months ago with no real answer! Guess it's just the way the components in the brick work, I can sometimes hear it when working on my mini, however this is on very rare occasions.

-Pos

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Answer 10

Nov 10, 2005 10:12 AM in response to Johan Wahlberg

Johan-

Guess what dude? I have the same thing happening.

Fortunately my mini is not where I sleep and is in a relatively noisy environment.

But I made it very quiet in the room, out the mini to sleep and listened. Sure enough, there it was.

Makes me long for a malfunctioning CRT HV supply, but I digress...

-DaddyP

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Answer 11

zenonox

Level 1

35 points

Nov 14, 2005 11:26 AM in response to Johan Wahlberg

You might want to enable the Safe Sleep mode:

http://www.hardmac.com/niouzcontenu.php?date=2005-11-13

Upon going into sleep, your mini saves the RAM data to the hard drive and subsequently "shuts down" (which means no power draw, thus no high frequency whining).

Powering up restores the RAM data in just a few seconds.

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Answer 12

Nov 14, 2005 5:39 PM in response to Johan Wahlberg

Johan,

I have noticed the same thing with my Mini's power supply, only when it is sleeping. I thought my ears were fooling me at first, but I did narrow it down to the power supply making a high pitched noise, too.

Aaron Boatwright

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