2009 Mac Pro Noise--how quiet should it be?

[FredT2]

I just got a 2.66 Quad-core Mac Pro. I've read a lot of comments about how quiet they are, things like "silent", "can't tell that it's running", etc. Mine is certainly quieter than my G5, but it is far from silent. I hear the typical high-pitched whine that I expect from computers, not loud, but there. But the sound that's starting to bug me is a low-frequency sound, almost like motor. It oscillates in volume from. It's not loud, but it has an irritating quality. I can't tell where it emanates from almost silent to too loud. It's not the graphics card or the disk drive, and all the fans are running under 1000 rpm. I'm guessing this isn't normal, but does anyone have an idea of where the sound is coming from?

Thanks.

 

[Shazaam!]

I've got the same machine and the same sound oscillation. I had Apple replace the power supply with no change.

The problem occurs because there's several fans running in there and intake and exhaust run at approximately the same rpm. When two devices run close to the same rpm or frequency (or multiples like 2X) they go in and out of sync. It's called "beating" where the sound peaks alternately reinforce and cancel each other. Made me nuts.

I found it helps to use the smcFanControl app to raise the rpm of the intake fan to about 830rpm. It also helped to turn the unit so that the CD doors faced towards me. My unit is below my desk and originally the unit rear and left side was close and parallel to a desk panel. This set-up amplified and reflected the sound. You could also try sound insulation panels on any nearby reflecting surfaces including the floor and underside of the desk.

 

[FredT2]

I've got the same machine and the same sound oscillation. I had Apple replace the power supply with no change.

The problem occurs because there's several fans running in there and intake and exhaust run at approximately the same rpm. When two devices run close to the same rpm or frequency (or multiples like 2X) they go in and out of sync. It's called "beating" where the sound peaks alternately reinforce and cancel each other. Made me nuts.

I found it helps to use the smcFanControl app to raise the rpm of the intake fan to about 830rpm. It also helped to turn the unit so that the CD doors faced towards me. My unit is below my desk and originally the unit rear and left side was close and parallel to a desk panel. This set-up amplified and reflected the sound. You could also try sound insulation panels on any nearby reflecting surfaces including the floor and underside of the desk.

Thanks Shazaam. I figured it was going to be something like that. I've had the experience too many times where most people say something is really quiet, I buy it, find mine is not so quiet, and then have to go through the process of determining whether the norm is what I have or not. Some of us are just more sensitive to noise distractions I believe. Anyway, I won't go through the bother of trying a replacement because I'm pretty sure it would not be any different.

 

[LurchNC]

Try lifting the latch that locks the side door on. See if that stops the "oscillating" sound.