amplify effect in chains

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amplify effect in chains

Permanent link to this post Posted by elg476 » Tue Apr 21, 2009 10:47 pm

Please excuse this naive, newby type question from someone who understands very little about digital audio. But I've wrestled with the docs and tutorials for quite awhile without finding an answer on my own. And by the way, I'm using Audacity 1.3.7 (beta) on Windows XP. So if I should be posting this question to a different forum, please let me know.

Question: is there any way to create a chain containing an amplify effect step that adjusts the amplification on each new file to achieve the maximum possible amplification without clipping? If so, to what value(s) (if any) should I set the "Amplification (dB)" and/or "New Peak Amplitude (dB)" parameters to achieve this?

To elaborate, each day I record between 5 and 10 audio files from a variety of sources. As they land on the disk, their peak amplitudes are all over the map: some are barely audible, and others are deafening. If I open one of the quiet ones in Audacity and then select "amplify" from the effect, its window comes up with the value of "Amplification (dB)" automatically set to the highest value it can achieve on the loaded recording without clipping.

I would like to create a chain to process these files in batch mode. And I'd like to insert an amplify step into that chain that behaves in the same way as does the amplify effect when I bring it up OUTSIDE a chain: in other words, I want the amplify window to come up and self-set its amplification parameter to the highest value it can achieve on the current file without clipping. But I can't figure out how to achieve this.

I've tried setting "New Peak Amplitude (dB)" to -0.0dB (because some of the docs I've read imply that that's the maximum amplitude one can achieve on any file without clipping -- I have no idea if that's true). I've tried setting the "Amplification (dB)" to some extreme number (say, 5.0) while leaving the "Allow Clipping" option unset. And I've even tried inserting an Amplify step while leaving the Amplify parameters completely alone without setting ANY of the. But in no case could I achieve the desired affect. Some files with low peak amplitudes were not amplified at all, and some with high peak amplitudes were amplified way past the point of a dull roar.

Is there any way to accomplish what I want?

Thanks!
elg476
 
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Re: amplify effect in chains

Permanent link to this post Posted by steve » Thu Apr 23, 2009 5:51 pm

elg476 wrote:I'm using Audacity 1.3.7 (beta) on Windows XP. So if I should be posting this question to a different forum, please let me know.

Moved to Audacity 1.3.x > Windows

elg476 wrote:Question: is there any way to create a chain containing an amplify effect step that adjusts the amplification on each new file to achieve the maximum possible amplification without clipping? If so, to what value(s) (if any) should I set the "Amplification (dB)" and/or "New Peak Amplitude (dB)" parameters to achieve this?

You need to use the "Normalize" effect.
The default parameters are:
ApplyGain=yes RemoveDcOffset=yes Level=0.000000
This will amplify each audio channel to a peak amplitude of 0.0
It will also remove any "DC off-set" (which is usually a good idea).

Note that whereas "Amplify" applies the same amount of gain to all audio channels, "Normalize" will amplify each audio channel independently to achieve the target peak amplitude in each channel (left and right are processed independently).
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)
steve
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