popping/click noise at beginning and end of recordings

[vicos]

Hi, I noticed that there was a popping/clicking noise at the beginning and end of every MP3/WAV a member of our team was recording. She was using Audacity and CoolEditPro

It is impossible to get rid of the click. If I trim the ends of the file, the click is still there. No matter how much you trim, the noise is still there on playback. Its like there is something about the format of the file that causes the player to burp. No one else on the team has this problem. Even bringing the problem file into a system that does not have the recording problem can fix the file.

Has anyone ever heard of something like this? The big question is if there is some way to salvage the files -- too many hours put into them.

[kozikowski]

Did you post in one of the other forums here? Anyway...

Before editing, remove the DC from the show clips and captures.

This location changes between Audacity versions...

Effect > Utility > DC Bias Removal.

You can't do this in Post Production. You have to do it to each clip before you start editing.

Whoever is producing these clips probably has bad equipment. I have two identical USB microphone amplifiers and one does this badly. The other is clean.

You can put a short quiet or silent segment of the work on the timeline and magnify it top to bottom. Completely quiet, correct work will settle around zero on the timeline. You probably have clips that look like the bottom illustration here...

http://audacityteam.org/forum/viewtopic ... 216#p41692

Koz

[vicos]

Thanks for the quick response. I looked and you were correct about the signal being off-center. I found that using the Normalize function fixed it right up

[kozikowski]

<<<I found that using the Normalize function fixed it right up>>>

That rings bells, doesn't it? Remove DC is available as part of Normalize in Audacity 1.2. You posted in 1.3 where it's not. Who's right?

Normalize is very dangerous to apply because it can alter the Stereo Image.

Koz

[waxcylinder]

Normalize is very dangerous to apply because it can alter the Stereo Image.

Koz

Unless, that is, you only use the Normalize function to remove the DC offset and don't do any real "Normalization"

I thought that the developers were planning to make DC removal a separate function, removed from the Normalize effect - but checking 1.3.5, 1.3.6 and 1.3.7 I can see that this is not yet the case.

WC

[AndyNewton]

Tip:

Another method that will remove a DC offset from a track is to apply a high-pass filter with the cut-off frequency value set to something like 10Hz.

Such a filter will have little effect on the sounds recorded, because 10Hz is below the range of our hearing, but any DC offset will be removed by the filter because DC is equivalent to a 0Hz ( zero hertz ) signal.

[steve]

Tip:

Another method that will remove a DC offset from a track is to apply a high-pass filter with the cut-off frequency value set to something like 10Hz.

Such a filter will have little effect on the sounds recorded, because 10Hz is below the range of our hearing, but any DC offset will be removed by the filter because DC is equivalent to a 0Hz ( zero hertz ) signal.

In several respects this is a better method than the DC off-set tool in the Normalize effect, however there is a small drawback in that this will sometimes leave a little click at the beginning. This is because there needs to be a minimum number of samples processed before the filter can decide what the frequency is. As you can see on this zoomed in screenshot, it takes a short while for the DC off-set to settle down to the correct level.

DC offset after passing through a 10Hz high pass filter

screenshot.png (5.22 KiB) Viewed 5534 times

If, as with most recordings, there is a bit of leading "silence" before the music starts, then it is easy enough to simply delete a little of the silence after running the high pass filter.

[Hellvin]

Just wanted to say thanks for the info on this page - I was having this problem and these posts helped me fix it.