Comparing Noise Level

[spurnell]

Hi, I am new to audacity and trying to compare the average noise levels in a mp4 file. I do not need dB levels, just a way to quantitively say on average this mp4 is this many times louder or quieter. Can I use RMS or LUFS to compare the files? The recording conditions are constant across the files (same microphone, same distance to microphone, etc.) Thanks

[kozikowski]

You can do that, but you may not want to.

Analyze > Contrast > Measure Selection. That's good for RMS (overall loudness).

But that will give it to you in dB. Measure both and write down the dB numbers.

Subtract the two dB numbers and divide by 20.

Then use your scientific calculator and take the anti-log base 10.

So measure one at -20dB (for example) and a second one at -14dB. There's 6dB between them. Divide by 20 and that gives you 0.3. Take the anti-log base ten of that and you get 2.

One is twice the volume of the other.

The problem with this, besides the math, is that one is not going to sound twice the volume of the other. The ear doesn't work like that. But anyway, that's how to do it. Give it a shot.

Koz

[steve]

Measure both and write down the dB numbers.

It's possibly a bit simpler than that. When you have two measurements in the Contrast effect, it will tell you what the difference is (in "dB RMS").
The difference in RMS is a common way to measure the difference in loudness.