can't find cause of intermittant noise on playback

[permutations]

I'm trying to record an audio book. I took all the usual noise reduction steps, and generally the recording is pretty good. But when I play it back, I sometimes hear distortion that is not on the wave file itself. If I play the segment of audio again, often it will sound clean. Also, I don't see the distortion in the visual wave - there's no noise to edit out.

It's not my speakers or the connections to the speakers. I tried playing it through my computer's internal speakers, and there is the same problem.

It's not the power going into my notebook because I tried playing the audio file with the notebook unplugged and it still happened.

It's not this recording because it happens with professional recordings that I know are clean.

The audio will sometimes sound like the voice is underwater, just for a second, or a syllable will be skipped. I realize this isn't an Audacity problem, but does anyone have an idea what might be causing it or how to fix it?

[george13]

The audio will sometimes sound like the voice is underwater, just for a second, or a syllable will be skipped.

This seems to me like artifacts introduced by the noise reduction. Like the program believes the voice to be noise and filters it out for a moment. Generally, the noise reduction is supposed to be much improved in Audacity 1.3 so you could try using the newer version. Or you could try lowering the amount of noise reduction or change the other parameters (I don't know what these are in Audacity 1.2). Good luck!

Also you say the original recording is of professional quality so you might not need so much processing to make it sound good.

[permutations]

I'm trying record an audio version of my book, so I'm noticing it when I play that back. It's happening before I do any noise reduction.

Also, it happens on files I did not record - that's what I meant about professional files that I know are clean. So I know it's a playback problem, and not related to anything about how the file was recorded. The noice is not in the sound file itself.

Sometimes it sounds like the voice is underwater, sometimes a syllable skips, sometimes there's a buzz. But if I play it again, these distortions won't be there and it sounds clean.

[kozikowski]

<<<It's not this recording because it happens with professional recordings that I know are clean.>>>

And it's a better than even bet that if you played your work on another computer, it would be fine.

Gargling underwater is a compression artifact. Is all your work MP3 or other compressed format? What happens if you select a representative portion of your live voice work and Export As WAV. Does that play OK?

If the problem suddenly becomes one of skipping instead of gargling, then your computer may not be up to this job. Tell us about it. Processor speed, memory, drivespace...

Don't muddy the water with stuff you captured from the Internet, that has its own problems. I'm only interested in recordings you made with your lips moving.

Koz

[permutations]

The noise (not necessarily the under water thing) happens when I play Audacity projects - not MP3. Also when I played a Daily Show clip on the internet. This is the professional clip I was referring to. I was trying to watch an interview and the noise in the audio was very irritating. I'm sure it wasn't in the original.

My computer is a Thinkpad T400, Intel Core Duo CPI P8600, 2.4GHz, 4GB RAM, 64-bit Vista OS. On the fast side.

[steve]

What is your sound card?

[permutations]

Not sure - whatever is inside a Thinkpad T400. Do you know of problems with specific sound cards?

[steve]

Lots of problems with internal PC laptop sound cards - basically they are usually poor quality, and crammed into a small space on the circuit board making them prone to picking up interference from other components such as the hard drive and fan.

[permutations]

Is the only solution a desktop computer? I don't have room for one.

[steve]

You can use an external USB sound card. I use a Behringer UCA 202. It is only suitable for line level sources (not microphones unless I also use a microphone pre-amp or mixing desk). One of the other regular forum contributors uses an Edirol ua-1ex. The Edirol is possibly a bit better, but costs a bit more. The Behringer costs around $30 US and I'm very happy with it (though the label peeled off so I glued it back on again).