Audacity Forum

As a new user to Audacity, I have observed something that I am unable to find an answer for.

When I make a recording (stereo), I notice that the baseline (if that is the proper terminology) of the waveform shown, does not line up with the 0 on the scale to the left of it.
This creates a problem when the recording is played, especially after an edit like changing the amplification because a noticable "click" is heard at the beginning and end of the recotding.

What does this scale represent and what can I do to prevent this from occuring?

This screen print should illustrate what I am describing.
I'd appreciate an answer or indication as to where I could go to find one.

George

The problem is called "DC Offset".
It should not happen when you are recording and if it does it indicates a problem with your sound card. Such problems are often due to faulty or badly designed hardware, though some users have reported that updating the sound card drivers may sometimes fix the problem.
I notice that you are using unusual "Quality" settings. 24 bit is a high quality setting, but 22050 Hz is a very low quality setting. Also, some sound cards have trouble with 24 bit recording, so I suggest that you try changing the Quality settings in Preferences and see if that improves things. Recommended settings for music recording would be: 44100Hz or 48000 Hz, and 16 bit or 32 bit. The default is 44100/32. CD quality is 44100/16.

Correcting the issue in post production (with Audacity) can usually be improved by one of two methods.
1) Use the "Normalize" effect - switch off the "Normalize to:" setting, but leave the "Remove any DC Offset" enabled.
2) Use a highpass filter set to a low frequency value such as 10Hz.

The second method will usually give a better result overall, but the first fraction of a second will not be corrected. If you can trim off the first second after correcting then I would recommend the second method. On recordings where you need the first half second, use the first method.

Thanks for that valuable information, especially about the sound card. I'm going to check into that right away.

It seems like an earlier version of audacity I used a long time ago, had some kind of a setting to remove DC offset, that was more apparent than 1.2 does.

I'll try your post production setting recommendations, but will strive to get things working right in the first place.

The recording I made was for a voice over (naration) to be used in a DVD video I'm making. That's why I tried to set the quality settings to match the software default settings I was using for the DVD. That probably isn't all that important.

A standard DVD uses 48000 Hz sampling rate. For DVD work, the ideal settings (if supported by your hardware) are 48000 Hz, 32 bit.

Thanks again
The sound card has the latest drivers and there doesn't seem to be any way to change the way it operates.

Both your suggestions worked well for the post production corrections.

I'll use your suggestions on the quality settings.