Set the same volume to 16 mp3 files (newbie asking)

[Gerardo]

Sorry. I know this has been asked before, but I know very little about Audacity and I would feel a lot more sure about trying out the solution if someone talks to me . I have used it a little bit before. Last year I removed the "emmmms..." from some voice recordings of interviews for example.

So I recorded my voice saying a speech in mp3. I now have 16 files; each one with one paragraph from the speech. I will eventually have to join them all together and it'll become the sound of a video. My problem is that the volume isn't the same on all the files. Can you please help me fix that?

On the forum, I read about normalizing and I also read about a plugin named "Chris's Dynamic Compressor plugin for Audacity". I also read something about "clipping"; don't know what that is. Do I have to install that plugin? Can you please help me with a step by step of what should I do?

Thank you very much in advance. So sorry for asking for a step by step I hope I won't be a newbie forever!

[DVDdoug]

Try MP3Gain. If it works for you, it's fully-automatic and it works without decompressing/re-compressing the MP3 which can degrade audio quality.

And, you might want to use MP3DirectCut to join the files, because it also works without decompressing/recompressing. (I don't have a lot of experience with MP3DirectCut so I can't help you much with it.)

If that doesn't give you good results you can use Audacity (and we can help you) but when you open a compressed file in Audacity (or any "normal" audio editor) it gets decompressed. If you then re-export as MP3 you are going through another generation of lossy compression and with MP3 the "damage" does accumulate.

On the forum, I read about normalizing

Regular normalizing adjusts the volume for a specific peak level (usually 0dB) but peaks don't correlate well with perceived loudness. There is now a "Loudness Normalization" effect built into Audacity.

and I also read about a plugin named "Chris's Dynamic Compressor plugin for Audacity".

That might help but I believe it was designed for music. Compression (and limiting) can make the quiet parts louder (or the loud parts quieter) whereas normalization makes the same adjustment to the whole file.

I also read something about "clipping"; don't know what that is.

Clipping is distorted flat-topped waves that happen if you try to go over 0dB digitally, or if you try to get 110 Watts out of a 100 Watt amplifier, etc.

Your analog-to-digital converter (recording), your digital-to-analog converter (playback), and regular WAV files are all hard-limited to 0dB and you'll get clipping if you try to go over. Audacity itself can go over 0dB temporarily/internally and MP3 files can go over 0dB, but it's bad practice to make a MP3 that goes over 0dB because the DAC will clip if you play it at "full digital volume".

With loudness normalization or RMS normalization you can end-up pushing the peaks over 0dB so you have to "be careful".

[Gerardo]

Sweet! Thank you DVDdoug.