Talk:Managing Computer Resources and Drivers

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Some Pops and Clicks when recording - and how I made them go away by increasing the data rate ( ! )

Here is a problem, and a fix I found. It makes no sense to me, so putting info here as a "Discussion". Perhaps someone can make something more logical out of this?

System: Dell Dimension 5150C - Dual Core Pentium D 3GHz - Windows XP Pro - Onboard sound SigmaTel C-Major Audio (no sound card) - Audacity 1.2.6

Results: Excellent results with above system. Sometimes in the past I have had clicks and pops when recording multi-track but problem went away so did not investigate. Yesterday downloaded an mp3 to use as a backing track and started to record my own playing, by microphone, as new tracks over the backing track. The imported mp3 track was perfect, but after 20 to 30 seconds of good quality recording of my own playing the Pops and Clicks problem occured - and this time it did not go away.

Diagnosis: Examined waveform in detail, expanding timescale to see the pops and clicks. Saw no overlaid spikes or any other transients. What I did see was discontinuities in the waveform at the single sample point level. The recorded waveform data points showed appearance as if a few microseconds of data had been dropped and the data points on either side then buttted up against each other giving an abrupt step in the waveform. Often these discontinuities occured in pairs a few milliseconds apart.

Fixing the problem: Tried many of the fixes recommended elsewhere in this Wiki but with no improvement. Even considered buying an external USB sound card (can't find any "PCI Express 1x" card to fit in my compact PC) - but I know the problem has gone away in the past so continued searching. Noticed that the mp3 import had a data rate of 44100 (shown at bottom left of Audacity screen). I usually use 48000 with good results. Changed data rate to 48000 - saved as an Audacity Project - recorded more live tracks by microphone - and no clicks or pops occurred!

Summary:

1) Find a data rate that works well on your system. Explore the higher rates - one or more of the higher rates may work well.

2) Be aware that when you import an mp3 track it may change the data rate to a rate that does not suit your system. Check the box at bottom left of Audacity screen to see the current data rate.

3) If imported data rate causes a problem with recording new overlaid tracks click on the data rate box to change it back to the rate that suits your system - even if that is a higher rate than the import. Save the import as an Audacity project to lock the new data rate before adding your overlaid tracks.

4) Export end result as mp3 etc for long term storage if desired.

This makes no sense, but it works on my system.