How to measuring the volume levels in Audacity in dBs

Hi Guys,

I have Two audio files of duration 1 hour. I want to compare the volume level difference between two audio files. basically there are same audio files which repeats after 7 secs. But 2 audio files are output of different devices. Can I compare that in Audacity ? What will be the accuracy and resolution in measuring the volume levels in audacity?
I changed the vertical scale to waveform in dBs. But its really hard to compare the 1 hour audio file. Can anyone please help me with this and please suggest me the easy way to deal with this issue?
I have also tried to plot the spectrum but again I can not see much difference. Can someone please help me with this?


It depends what you mean by “volume”.
It is easy to measure the “peak signal level” (the “Amplify” effect will indicate how much below 0 dB the biggest peak in the selection is). Measuring “loudness” is a completely different issue (see:

There is an application called [u]Replay Gain[/u] that adjusts the volume at playback-time. The intention is that all of your music files will play back at about the same volume. Apple has something similar called Sound Check for iTunes & the iPod. The catch is, your player or player application has to support it.

[u]WaveGain[/u] and [u]MP3Gain[/u] use the same underlying loudness algorithm as ReplayGain, but they actually change the volume of the file so you don’t need any particular player or player software. Assuming you have WAV files, you’ll want to run WaveGain.

If you go above 0dB you get clipping (distorted flat-topped waves). You can have a quiet sounding file with some 0dB peaks (the “digital maximum”), and you can’t increase the volume of these quiet files without clipping. So, ReplayGain (and related programs) will tend to reduce the volume of most files.

If you find that the files are too quiet after running WaveGain, you can run Audacity’s Amplify effect to see how much “headroom” you have (if any) on each file. ( Don’t actually change the volume 'till you’ve checked both files). Then choose the file with the least headroom as your reference, and increase both files by the same amount.


There are several things that make this complicated… Loudness correlates very poorly with the peak level. Quite sounding files often have high short-term peaks. Loudness is more related to the average/RMS level and the frequency content. And, what do you do with a file that’s quiet for the 1st half and louder for the 2nd half??? (You can manually adjust it, and there are “leveling” tools, but that’s not what we’re doing here.)

Hi Steve,

Thanks for your quick response.

I’m not familiar with audio terms or audacity. The Amplify effect will show me the peak value, not the average value of total 1 hour audio file, If I understood correctly. Yes you are right, I want to check and compare the loudness of audio files. Is it measured in dBs?

Can you please help me with that?


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