Comparing SPL or measuring SPL with Audacity?

I understand a little bit about sound measurements, for example I know that 20db is roughly twice as loud as 10db. It is basically a log scale (maybe not exactly but that is how I look at it.) Ok. So with that said here is what I’m trying to do, with Audacity if possible. My office has a tower server in it next to my desk. It is about as loud as a large desk fan. I don’t know the exact SPL. I’ve found some fans that are supposed to be 40db (or less depending on RPM). I want to somehow measure the current “loudness” of my server’s fans and then compare to 40db to see it would be better or worse to replace.

Is this something I could do with Audacity or should I just spend the $20 or so on new fans and take my chances ? :open_mouth:


Bill W

You would need to use an SPL meter.
The level of a recording depends on many factors including the sensitivity of the microphone, the distance from the sound source, the recording level settings. You can’t achieve any meaningful SPL readings unless the system has been calibrated.

…with one of these…

Radio Shack has been offering an SPL meter for years. I have the older analog one and the company has the early digital version.

You do need to be careful with fans. You need to measure the noise without getting the actual airflow in the mix. You may perceive it as a nice cooling breeze, but the a sound meter may interpret it as an explosion-level sound event. “A” curve SPL is designed to minimize this effect. It takes into account your ear characteristics.

And no, you can’t get Audacity and a microphone to do this. Too many variables and unknowns. You can, however, do a relative measurement. Do a measurement and Don’t Change Anything and do a second measurement. Given you do everything right and don’t overload or hit the noise floor, that difference should be close – in the “C” or flat weighing, not the “A” weighing that’s written into law.


Hmmm…well, just not worth it to me at this point to buy an SPL for $50 or so to test fans that will cost me less than $20. so I guess I’ll just buy, plug em in and use my ears to see if there is a difference.

Thanks anyway for taking to time to look at this crazy idea.

Bill W