CPU fan noise

Kevin Maxson · Post by **Kevin Maxson** » October 29th, 2009, 7:42 pm

Hello, all.

I'm trying to do a long recording, and I can't keep my
CPU fan from making a guest appearance. (It's a Pentium 4.) No post filtering seems to be good enough w/o lowering my volume too much. Worse, sometimes it kicks into high RPMs under load, making a louder, higher-pitched noise for a few seconds until it fades back down
to its normal hum. In other words, for a long recording, it can be variable.

I'm using Audacity beta and a Samson C01U. Thoughts on isolating this?

- Kevin

BellonaTimes · Post by **BellonaTimes** » October 29th, 2009, 9:08 pm

This happens with mine in depths of summer, even with the a/c on. If you have the space in your computer room, and a long enough mic cord, I'd get as far from the source as possible. You also might want to try bringing the thermostat down in that room, if possible, or buy a small a/c unit.

Steampunk · Post by **Steampunk** » October 29th, 2009, 9:33 pm

As BT says, distance is a good noise reducer. You can also play to your microphone's recording characteristics.

These mics (i.e. those designed for vocals) usually have what's called a hypercardioid or supercardioid directionality. That means your mic will pick up sounds directly in front or back of it more, and less on the sides. Think of your mic as a clock with 12 o'clock being the part facing you and 6 o'clock being where the cord is. The least sensitive pick-up will be at around 4 o'clock and 8 o'clock. Try to position your computer in one of those "dead" zones. That should help, too.

Jim

jimmowatt · Post by **jimmowatt** » October 30th, 2009, 2:21 am

You could also try lowering the recording level a little and speaking a little louder. If the contrast between your voice and the background noise is greater then it's going to sound less irritating in the final recording.

RuthieG · Post by **RuthieG** » October 30th, 2009, 4:17 am

Kevin Maxson wrote:Worse, sometimes it kicks into high RPMs under load, making a louder, higher-pitched noise for a few seconds until it fades back down to its normal hum. In other words, for a long recording, it can be variable.

Kevin, I suffer from the same problem. I use a Samson Q1U which is quite similar to the C01U.

Make sure you have the minimum number of programs running when you are recording: just Audacity and your text source. (Obviously there will be other processes running like AV and firewall, but try not to have much else.)

If you become aware that the high revs have started, leave 5 seconds of ambient noise in the middle and use that as your sample for noise-cleaning that passage only. Use the normal ambient noise for the rest of the recording. It will take more time in post-processing, but not that much, and it is worth it for a good result.

I don't find Audacity's noise-cleaning particularly effective for my kind of noise. I export as a .wav from Audacity and do noise-cleaning in the basic free version of Wavepad, as follows: Effects | Noise Reduction | Grab Noise Sample from Selected Area. Then Select All, | Effects | Noise Reduction | Apply Spectral Subtraction Based on Noise Sample). I then save the .wav and re-import into Audacity, where I do anything else necessary (sometimes a quick light run of noise removal if Wavepad has left any tinkly artifacts), and export as an MP3 from there.

It sounds fiddly, but I have got into that routine and I find I end up with a perfectly clean recording.

An alternative might be, if the fan only does it for a few seconds, just to stop speaking until it has settled back, then cut out the noisy "silence" bits afterwards.

I haven't tried this, but I keep meaning to: attaching some acoustic foam to the underside of my desk.

Ruth

icyjumbo · Post by **icyjumbo** » October 30th, 2009, 7:01 am

I'm not sure how much the acoustic foam will help with fairly low frequency noise like fan noise. Basically, the only way to attenuate such low frequncies is to put a lot of mass between the source and the mic, as far ascI can tell from my Internet research. If so, then the advice about distance is a good bet: get a USB extension cord

Hazel Pethig · Post by **Hazel Pethig** » October 30th, 2009, 7:47 am

I just bought a new mic for my daughter and it has a 5 foot cord on it. simple solution. Distance. If your mic has a long cord, sit at the other end of the table.

--Hazel

Shipley · Post by **Shipley** » October 30th, 2009, 8:15 am

And, of course, if your microphone does not have a long cord, both USB and 3.5 mm jack extension cables are readily available!

thistlechick · Post by **thistlechick** » October 30th, 2009, 8:48 am

The problem with a long cord though is that one still needs to be close enough to the monitor to read the text from the computer screen

Hazel Pethig · Post by **Hazel Pethig** » October 30th, 2009, 12:40 pm

Sorry I didn't think of that. You could print your text if the fan noise is a huge problem.

--Hazel

Kevin Maxson · Post by **Kevin Maxson** » October 30th, 2009, 1:10 pm

thistlechick wrote:The problem with a long cord though is that one still needs to be close enough to the monitor to read the text from the computer screen

Yep - figured that already. And also to reach the keyboard/mouse for start/stop.

Starlite · Post by **Starlite** » October 30th, 2009, 3:48 pm

Or throw out the computer and get one of these:

http://www.samsontech.com/products/productpage.cfm?prodID=1916

Only drawback is if you want to get away from the computer (like me), you need to print the bits out or have a paper copy... ie real book to read from. I am always scanning the charity shops and garage sales for oldies!

Esther

Post by **Availle** » November 3rd, 2009, 6:35 pm

Hi Kevin,

I just stumbled across your post, and maybe I can help with the fan-spiking problem.

Are you sure it spikes under load only? Then it may be a good idea to reduce it, as mentioned above.

Otherwise, the following can happen: Say your fan kicks in whenever the temperature is reaching, say,45 degrees, then it turns faster until the temp drops under, say, 38 degrees, then it stops (or goes slower). In such a case, reducing the CPU-load is not helping at all, on the contrary, you'd want to increase it such that the temp stays comfortably above 45 degrees, so that the fan is in constant motion.

This will not take care of the fan noise as such, but it will avoid the spikes, and a constant hum might be easier to clean.

If you don't know how to raise your CPU-load, why not help finding a cure for Terry Pratchett's alzheimer while recording: http://folding.stanford.edu/
Every minute helps...

Caliban · Post by **Caliban** » November 20th, 2009, 10:17 am

There is a technique from the early days of recording (especially when sound was new and camera's were noisy) called "Blimping". Essentially they just wrapped the camera in blankets. See if you can get inventive with a few blankets and a cardboard box. The trick here is to attenuate the fan noise but still keep adequate airflow to cool your cpu.

Cleaning the case and heat sink might help too.

Hope this helps.

Cal

Kevin Maxson · Post by **Kevin Maxson** » November 21st, 2009, 2:14 pm

Thanks, Cal.

I'm going to give it a shot with my laptop, but after that then I'll definitely try the blanket route. I'm also tempted to build a little three-sided enclosure with a roof lined with acoustic foam that I can place over the chassis when I record.

Or, perhaps Santa will bring me a whole new computer. I wish I could hear how loud their fans were on-line before I buy.