Create a room noise profile to auto remove from measurements?

[whazzup]

I noticed even when I switched off everything in my room, I have a 38hz and 50-60hz ~10+db hump that my mic is picking up. Any way to remove that from the measurements with some sort of noise profile?

 

[John Mulcahy]

If you have an analog mic, so output and input are both on the same soundcard, using multiple sweeps can help to suppress background tones.

 

[whazzup]

Thanks for the reply! I use umik-1, can I do that still?

 

[John Mulcahy]

Afraid not, multiple sweeps are disabled when the input is a USB mic as there will be slight differences in the sample clock rates on the soundcard and the UMIK which cause problems with the averaging of multiple sweeps.

 

[whazzup]

Afraid not, multiple sweeps are disabled when the input is a USB mic as there will be slight differences in the sample clock rates on the soundcard and the UMIK which cause problems with the averaging of multiple sweeps.

So if I have an analog mic, plus probably an audio interface like maybe this: https://www.amazon.com/Focusrite-Scarlett-Audio-Interface-Tools/dp/B07QR6Z1JB/
I would be able to use suppress background tones in REW? How does averaging of multiple sweeps in REW cancel out the unwanted background noise? This is an example of my room, with only my computer running (aircon off).



Can give me a rough breakdown of the steps or the functions I should look into / read up on? Sorry to trouble you!

 

[John Mulcahy]

If the background is predominantly tones (e.g. compressors, fans, mains hum) their influence can be reduced by the synchronous pre-averaging of multiple sweeps. The phase of the background tones will be different for each sweep so when the sweeps are averaged the sweep signal maintains its level, since it is the same every time, but the background is reduced. That also works to reduce the effect of random background noise. The effect isn't huge, about a 3 dB improvement overall for each doubling of the number of sweeps, so around 9 dB for 8 sweeps.

Using longer sweeps also helps, since the longer the sweep the more energy it has compared to the background. There is a similar 3 dB improvement for each doubling of sweep length, longer sweeps can be used with your UMIK as well.