Filters to match volume levels


I am a complete amateur at audio editing and want to ask this probably simple question. I have these 2 audio files:

which I’ve used MP3Gain to ‘apply max no clip gain for each file’. The trouble is they have wildly different volumes now. If I make the first file 88.4 dB to match the second file they are both too quiet. What I want to do is make the second file the same volume as the first (or as near as possible) and without any clipping.

Can I use Audacity to achieve this? If so, how? I guess I’m really asking which effects I need to apply…


Audacity is v2.0.2
OS is Windows XP

How will you be playing the MP3s when you’re done?

On a laptop through the speakers. I should perhaps also mention that they are audiobook files.

and what media player will you be using? I presume that it supports MP3Gain?
Are the files already in MP3 format?

It’s not that simple… Loudness is realted to the average level and some other factors, whereas clipping is determined by the peak level. Many quiet-sounding songs have one or more 0dB (100%) peaks, so you can’t increase the loudness without clipping (distorting). “Equal loudness” and “loud” are often conflicting goals! :frowning:

which I’ve used MP3Gain to ‘apply max no clip gain for each file’. The trouble is they have wildly different volumes now.

If you don’t allow clipping (and you usually don’t want clipping) there is obviously a limit to how much MP3gain can boost the volume, if it can boost it at all.

If I make the first file 88.4 dB to match the second file they are both too quiet.

Since we have a 0dB peak limit, most of the time if you want to match volumes, you have to reduce the loud-song song rather than boost the quiet-sounding song. That’s just math… It’s not MP3Gain’s “fault”. MP3gain (and RelayGain, etc) will end-up reducing the volume of most songs. You can increase the target-volume for MP3gain, but you are giving it less “room to work”, and you’ll end-up with a bunch of unchanged files (if you don’t allow clipping).

I see a big peak in the “quiet” file. You can try some dynamic compression (Effect → Compresssor) or a limiter plug-in to knock-down the peak. Compression/limiting is most-often used to boost the average level without boosting/distorting the peaks. If it’s over-done (as it often is with popular music) it can make music boring by making it “constantly loud”. And, if you really over-do it, you can get distortion or other side-effects.

There’s one more thing you can do… After running MP3gain, run Effect → Amplify. Note the default amplification and cancel. The default is the amount of gain you can add (if any) without clipping. Choose the smallest default amplification of both files, go back and re-run Effect → Amplify, applying that smaller gain to both files.

It will also help you have original uncompressed files, so you can apply ReplayGain (or WAVEgain) before MP3 compression. MP3gain works only in 1.5dB steps (due to a limitation of MP3), and the lossy MP3 compression causes some peaks to be higher and other peaks to be lower. The higher peaks effectively force a lower gain-before-clipping limit.

And, any editing in Audacity (or any “regular” audio editor") requires the MP3 to be de-compressed. You go through a 2nd lossy compression step if you re-save in MP3 (or other lossy format).

Wouldn’t the Brick Wall Limiter plug-in be of use here?

and the second file has a large peak which you could just lower with the pencil tool.

I don’t know that I ever heard Brick Wall sound very good, but that would get rid of the peaks.

Please note that the loud performance is almost a solid block of blue where the quieter performance has variations, moving levels, expression and theatrical interpretation. Compression is about the only way you’re going to make the bottom one sound and look like the top one – reduce the high peaks, bring up the low volumes and advance the whole package so it’s as loud as possible. We don’t necessarily advocate that last bit, but it looks like what the producer of the top performance did.

You might try Chris’s Compressor at the default settings. These two samples look a lot like what my productions look like before and after.

Change the first value, Compression from 0.5 t 0.78 before you apply it.


If the object of the exercise is to make the tracks have about the same loudness, then MP3Gain is the way to go, but I’m not sure that you are using it correctly.

If the object of the exercise is to make all of the tracks “loud”, then compression and/or limiting is the way to go, though this will reduce the “expressiveness” of the quieter tracks and will reduce the sound quality of all MP3s that you process.