pop noise when recording

[J. Baker]

I seem to get a pop noise when recording at either 48000 or 96000 Hz. 441000 Hz seems fine. I tried recording with a few other audio editors at 48000 and 96000 Hz and all was fine. Any tips or is this a bug? Thanks

[AndyNewton]

I have had scatterings of "pop noises" when recording, using Audacity 1.2.6. And the pops occured, or not, dependant upon the project sample rate. So this may be a general issue with PC / sound card speed and setup - not something specific to version 1.3.

On my PC the sample rate that gives no pops is 48000bps, but 44100bps pops all the time!

Zooming into one of my "pops" until individual sample dots were visible showed that the pops were not anything added onto the recorded waveform but were in fact places where a brief part of the signal was missing and two parts of the waveform were butted together with an abrupt vertical step between - creating a pop sound when played back.

My fix is to always use a project rate of 48000bps, and that is good enough for my purposes at present. I have to keep an eye on project rate if I import an mp3 backing track into Audacity because that can reset the rate and I have to change it back to 48000 before doing any sound recording over the backing track.

[AndyNewton]

Continuing from previous post: Now in Audacity version 1.3.3 Beta . . . .

Have just now installed the Beta version. Doing a few tests. ( OOOh I do like the improvements ! )
But - the "pops" due to time discontinuities in the recorded waveform are much worse in Audacity 1.3.3 than in the stable 1.2.6 version.
The pops happen on my PC at 44100bps and 48000bps and 96000bps.
So using 1.3.3Beta there is no high quality sample rate that gives me pop-free recordings.

But 1.3.3 appears to have a number of new setup and adjustment features. I will try some experiments with those.

[AndyNewton]

Doing some more careful testing in Audacity 1.3.3 Beta. Two types of click/pop artifacts detected, and I can't find any combination of settings that stops both types of clicks happening. (Though in Audacity 1.2.6 at 48000Hz sample rate I have no clicks at all.)

Dell Dimension 5150C Dual Core Intel Processor with SigmaTel onboard sound.
Windows XP Pro SP2
Recording device Windows Direct Sound: SigmaTel Audio
(OK I know , but it works perfectly with Audacity 1.2.6, and there is no sound card available to fit this compact PC anyway.)

CLICKS OF THE FIRST KIND:
Recording from Line In, or Front Mic, or Rear Mic, but with no sound signal applied, the recorded track shows regular clicks. These are very low amplitude - but significantly greater than the background hiss. Clicks are only a few sample points in duration.
Leaving mic or other inputs unchanged, and running Audacity 1.2.6 picks up only silence, and when amplified all I see and hear is white noise. So clicks are not being picked up from outside and fed into the inputs - they are being generated inside the PC, but only when running Audacity 1.3.3.

Changes tried that did not stop or change the clicks:
Recording device = Windows Direct Sound: Primary Sound ... (remaining text is outside viewable area of dialogue box item)
Audio Buffering = 5ms, 50ms, 100ms, 500ms, 700ms
Latency Correction = 0ms, 5ms, 20ms
Sample Format = 32bit float, 24bit
Audio Cache Always hold in memory = on / off
Dual processor PC - set processor affinity of Audacity to single processor
Set Audacity windows priority to High
Play other track whilst recording = on / off

Changes tried that did modify or stop "clicks of the first kind":
Mono recording
Sample rate - clicks ....
8000 - One click every 0.410 sec
16000 - One click every 0.410 sec - each click is a little wiggle at 1 sample point and then a peak at 1 sample point
22050 - Lower amplitude clicks, intermittent at semi-random periods of 0.400sec, 0.822sec, 1.622sec, 0.401sec, 0.421sec
44100 - No clicks ( ! )
48000 - One click every 0.411sec or 0.401sec - each click is a little wiggle for 4 sample points and then a peak at just 1 sample point
96000 - One click every 0.410sec - each click is a little wiggle for 8 sample points and then a 4 sample point slope up to peak.
Set Stereo Recording, at sample rate of 48000: Clicks on both L&R at regular intervals of 0.620sec. (Is that a clue?)

CLICKS OF THE SECOND KIND:
As sample rate of 44100 gives no clicks of the first kind I tried to do some multi-track recordings, laid down one mono track at a time from microphone. Duration of each track just over one minute.
Track 1 - clean, no clicks
Track 2 - clean, no clicks
Track 3 - fairly loud click or pop type of sound at 11.9sec in, and 55.3sec in. Zooming into the click shows a smooth sound waveform either side of a single sample point width discontinuity - the waveforms either side are butted together but they don't fit!
Track 4 - a lot more clicks. Zooming shows all these are discontinuities in waveform as track 3. Two clicks at 11.28sec separated by 96 sample points, Two clicks at 11.35sec separated by 36 sample points, Too many to count at 26sec, More at 40sec, 56sec and 71sec.
Some of these clicks of the second kind were at peaks in the audio, some at constant mid volume audio, and some during times when audio was reducing. None occured during silent periods (but of course a discontinuity in a string of zeroes is still a string of zeroes!)

Enough testing ..... I would like to use Audacity 1.3.3 but until these clicks are all fixed I will have to revert to using 1.2.6.

[J. Baker]

If I remember right, I was having the same issues with 1.2.6 as well. But I can try and test it again.

[AndyNewton]

It seems we are both in the same boat JB.

I can use Audacity 1.2.6 - but only because at one specific project sample rate (48000) there are no pops on my system.
And you can use Audacity 1.3.3 - but only at one specific project sample rate (44100) with no pops on your system.

It would be great if someone could tell us how to stop the pops in Audacity 1.3.3 - at all project sample rates.

[webmailusr-msn]

It also happened to me... I was recording a song from the windows mixer (stereo input), since the microphone input didn't record nothing (another bug?), using audacity 1.3.3 beta

I realized there was a periodic "tic" "tic" "tic" noise like about each 1 or 2 seconds, and it seems that it was fixed (or at least reduced), by adjusting the sampling rate. My PC is a sony vaio dual core, Win xp home sp2, 1GB RAM, audio ASIO SoundReality from SigmaTel, and in advanced properties I tried several sampling rates, also in audacity options. Finally what seems to work is having 48khz in the sound card and 44.1khz in audacity... looks funny but worked!. What I'd like to know is what's happening, so I can make those adjustments in a "scientific" way, and not only trying it...

Regards...

[AndyNewton]

For a brief moment (just long enough to do a post) I thought I had traced the source of the regular tick-tick clicks in my Audacity 1.3.3 recordings. Actually the clicks are still there at all project rates except one - I just forgot Audacity was set to that one project rate.

However, this is still a useful find that may help some of us:

How to stop Norton Antivirus scanning each .au data file that Audacity opens during recording.
(These details are specific to Norton Antivirus, but the principle should apply to any other brand of virus scanning software.)
Open Norton Antivirus or Norton Internet Security from icon at bottom right of screen.
Click on Options at top of Norton window and select Antivirus.
Select Auto-protect in menus at left of Norton window.
Under "Which file types to scan for viruses" click to select "Scan Files Using Smartscan", and NOT "Comprehensive File Scanning".
To maintain effective virus protection click on the Smartscan Customise button and click Defaults in the file types list window.
The Default list of file types is massive, so Antivirus will still check virtually every type of data file but not .au files because ".au" is not on the default list. (The Comprehensive File Scanning option blindly checks every data file regardless of its file extension type - so I assume it will be scanning all the .au files opened on-the-fly during Audacity recording - not a good idea.)

Is this safe? My uninformed view is that it is safe because I do not ever receive .au files from the internet or on media cards etc. The .au files are all generated inside my PC, by Audacity, and so they cannot be a route for infection to enter the PC.

Now back to the hunt .....

[Document02]

Hello everyone,

concerning clics of the first kind:
OK, ran about 80% of the tests described by Andy Newton, with same results (audacity 1.3.3, 1.3.4 and 1.2, regular clics at 48/96kHz), before reading this thread:
Same results with the change of sample rates
Same results with changes of buffer.

clicks are every 0.417s (one "point" of the data is at zero).

Additional tests made:
change of the soundcard sampling frequency (44.1 / 48 / 96 kHz) and latency: no changes in audacity clics
tests through other softwares : no clics
started recording from somwhere else than zero. then aligned the track at zero. clicks are still every 0.417s


concerning clics of the second kind: I have them also, but the frequency depends on number of tracks, length of tracks etc... I guess this is a CPU load issue.

I hope a solutions is found..

[alatham]

Making Virus Checkers stop looking for .au files is a good idea. Those .au files are audio files and aren't executable so you can't get any viruses from them.

The threat of computer viruses is way overblown. As long as you know what you're doing (and you keep your computer updated), you can avoid using one completely. I haven't used a Virus Checker in at least 5 years.

Caveat: I'm not recommending doing without Virus Checkers, I'm just saying it's possible to do so. Reader beware.