Amplify multiple files to same volume

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Amplify multiple files to same volume

Permanent link to this post Posted by pthubbard » Thu Jan 28, 2010 8:50 pm

How could I use Audacity to change the db level of multiple .mp3 files to a consistent maximum? i.e. all to 89db. This would involve lowering some and increasing others. The amplify feature seems to only tell you the maximum increase (w/o clipping). I would like all files to be the same volume so that I don't have to constantly change the volume as I'm listening to different pieces. Thanks!
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Re: Amplify multiple files to same volume

Permanent link to this post Posted by billw58 » Thu Jan 28, 2010 9:33 pm

Use the Normalize effect and set how close you want each file to be to 0 dB. For example you could Normalize each file to -3 dB. Although I don't understand why you wouldn't want to maximize the volume of each file, which would accomplish the same end.

Although it is a sad fact that normalizing a group of files so the peak level is identical in each file does not guarantee that each file will "sound" equally loud. That is dependent on the dynamic range of each file and the amount of dynamic compression applied to each song during the recording/mastering process.

-- Bill
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Re: Amplify multiple files to same volume

Permanent link to this post Posted by pthubbard » Thu Jan 28, 2010 10:49 pm

Thanks for the response. I'm used to using mp3Gain to do what I'm talking about. If you're familiar with it, it has a feature that sets all selected tracks to the same db level (89db is the default which I usually use) unless clipping would occur in which case it sets it as close to 89 as it can without clipping. I would continue to use mp3Gain except it doesn't seem to work well with Windows 7/64bit. As I understand it, Normalize would adjust both left and right channels to the same level which might not be desirable if one channel is supposed to be quieter. Would Amplify achieve the result I'm looking for? Also, what would be the difference between mp3Gain's setting of 89db and Audacity's 0db. Your point about setting them all to max seems to make sense... would they all be roughly the same volume?
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Re: Amplify multiple files to same volume

Permanent link to this post Posted by billw58 » Fri Jan 29, 2010 12:03 am

I'm not familiar with MP3Gain. Their setting of "89 dB" doesn't make sense to me. In Audacity, as in most (if not all) digital audio editors, 0 dB is maximum volume. Anything less is specified as a negative value, e.g. -3 dB.

If you are concerned that Normalize will adversely affect the stereo balance, then Amplify is the way to go. Just accept it's default settings and it will maximize the volume of the selection.

You might want to investigate "Chains": http://manual.audacityteam.org/index.ph ... dit_Chains

This allows you to batch process files. But Amplify is not the effect to use in Chains as the parameter that is retained is the amplification factor, which may necessarily be different for each song. Normalize is better in this respect as the retained parameter is the desired maximum level.

And as I said, the perceived "loudness" of a track does not necessarily relate to the maximum peak amplitude. http://en.wikipedia.org/wiki/Loudness_war

-- Bill
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Re: Amplify multiple files to same volume

Permanent link to this post Posted by kozikowski » Fri Jan 29, 2010 12:20 am

Audacity is doing what MP3Gain claims to avoid. It does peak normalization.

MP3Gain does not just do peak normalization, as many normalizers do. Instead, it does some statistical analysis to determine how loud the file actually sounds to the human ear.

So we can't do what you want.

We do have a plugin called Chris's Compressor which will certainly do all those jobs and very well, too. It was designed to even out volume variations to your ear, but it's not an internal Audacity tool and last I looked, wasn't on the list of tools that you could chain.

Chris's Compressor
http://pdf23ds.net/software/dynamic-compressor/

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