Applying MP3 chain drastically changes the size of waveform

[Code-E]

Hey there,

I've come across my old CD stash and, using info found in the Audacity manual, imported them with CDeX and now I'm applying the MP3 chain. But not knowing much about this process when I noticed how much it seems to be changing the waveform I got worried I've done something wrong along the way.

I've attached a before and after, but the weird thing is that it seems like some songs have a more drastic change. Also some songs seem to already be maxed in the waveform, so the Normalize effect lowers it.

I couldn't actually tell any difference by the audio, but if I'm going to through ALL of my old CDs I may as well do it right.

[Not really sure how to use images on this forum. Couldn't find a function to make the images take up less space]

pre-normalize

pre-normalize.png (87.27 KiB) Viewed 283 times

post-normalize

post-normalize.png (152.91 KiB) Viewed 283 times

[kozikowski]

my old CD stash

What's the music? Head-banger Rock?

imported them with CDeX

Are you sure you imported the work digitally with CDex? Did you have any other cables between the player and the computer? The blue waves have the signature of a very common analog error.

Can you say the reason you're converting all your work to MP3? This may be a good time to resolve the format issue.

Koz

[DVDdoug]

Yeah... Something is wrong if your ripped files are clipped at 0.5 (-6dB) before you do anything. Some modern "loudness war" CDs are clipped at 0dB (1.0).

Also some songs seem to already be maxed in the waveform, so the Normalize effect lowers it.

Yes. I'd guess that more than half of commercially released music is normalized/maximized at 0dB. If you normalize to 0dB nothing will happen, but of course if you normalize to less than 0dB the volume will be reduced.

MP3 is lossy compression and the wave shape does change slightly. Some peaks get higher and some peaks get lower. So after converting to MP3, some peaks may go over 0dB and Audacity may show potential clipping. (The MP3 can go over 0dB without clipping, so the MP3 isn't necessarily clipped but if you play it full-digital volume into your DAC, you DAC will clip at 0dB.)

[Code-E]

What's the music? Head-banger Rock?

Nope, if I remember correctly this came from a hip-hop album.

Are you sure you imported the work digitally with CDex? Did you have any other cables between the player and the computer? The blue waves have the signature of a very common analog error.

Can you say the reason you're converting all your work to MP3? This may be a good time to resolve the format issue.

Koz

The player is an external drive connected to my powered usb hub. I didn't realize that could have an effect.
But now that I've thought about it, this may be a bad example because it came from a CD that was burned for me years ago. I can't imagine that would come out well, so that may be what you're seeing.
(EDIT: Having checked a few of the other files that were imported from a burned CD, not all of them are that small of a waveform.)

I also forgot to mention that I'm importing them as WAVs to have a digital backup, and converting to MP3 for use...I haven't fully given in to streaming services just yet. I like to have my music files on my phone or computer.
If that's what you were asking, otherwise it's only MP3 because that's the chain that came with Audacity. I'm sure FLAC would be a better option even though it takes up a bit more space.

On top of this problem I've noticed that many of the files seem to have very small parts of the next song in them, or start a fraction of a second into the song. So I'm going to have to learn how to fix that and re-import many of the CDs.