Amplification anomaly

Audacity Help Forum macOS
1

I have recorded hundreds of concert recordings, editing them in Audacity. I always amplify the files to -1dB.
Recently I recorded yet another classical concert.
For the first half of the concert, Effect>Amplify…, yielded Amplification (dB): 7.5 and New Peak Amplitude -0.0. This is quite common for me, and it allows me to enter the New Peak Amplitude to -1.

However, the second half of the concert, Effect>Amplify…, yielded Amplification (dB): -50 and New Peak Amplitude 398.8219.
The screen waveforms appear very similar in amplitude for both recordings.

I have changed the Amplification (dB), to 7.5 but the New Peak Amplitude rises to 456.3219. Nothing alters the New Peak Amplitude.

  • I have tested the recorder, and it works OK.
    I have restarted the computer, and reverted to Audacity 3.2, but no joy.

This all means that I can’t match the level of the first and second recordings.
Any thoughts about what’s happening, and/or how to fix it.

Audacity 3.2.1
Mac OS 10.13.6
Recorder Sound Devices MixPre-10

2

Nothing rings a bell, but I know where to start looking.

Make sure you have a perfect quality backup of the second segment.

Open the segment and display the whole thing. I think it’s still Command+F.

Drag-select about the first third (not important). Delete.

Drag-select the last third. Delete.

Pretend what’s left is your desired show. Do your tools work now?

Koz

3

Drag-select about the first third

Start about a third of the way into the show and drag to the left. Make sure the beginning of the show goes away.

Same with the end. Make sure the end of the show is deleted.

Koz

4

So you have a little boo-boo in there that doesn’t belong. You should be able to locate it in a fashion similar to what koz describes. Then Zoom in and delete the little sucker.

The “50” is the arbitrary maximum imposed by “Amplify”. The negative number indicates that there is at least one sample in your audio that is a large floating point number, in your case possibly very very large.

So it appears there was already some processing done on your audio.

I once had a stereo track of fairly low amplitude. I split the track to mono, and then did a mix and render. This resulted in a suggested amplification of -5. I was stunned, as the original audio was so low. Then I zoomed into the track and during the first second when I had turned on the stand-alone recorder, I saw a large glitch, resulting from me bumping the microphone. I don’t think that was the case here, as your number is so large. But the point here is that any processing, including a mix and render, can create samples that are greater than 1 = maximum.

If you did not do any processing, then there is a glitch somewhere.