If you have problems with crackling audio, first check whether your problem seems to be hardware specific or application specific. 

If the problem is hardware specific, it might be that the position reports coming in from the hardware is bad, and here are two things to try in that case. If it does not seem to have any effect, please remove the workaround again.

=== Position_fix quirking ===

If this affects your HDA Intel sound card, there are two methods the driver can read the position reports. 
You can test the two different methods by editing the /etc/modprobe.d/alsa-base.conf file, and add either
{{{
options snd-hda-intel position_fix=1
}}}
or 
{{{
options snd-hda-intel position_fix=2
}}}

After editing the file, reboot your computer for changes to take effect. 

(Technical info: position_fix=1 will read the position from the LPIB register, and position_fix=2 will read from the DMA position buffer map. The latter is the default for most chips.)

=== Turning off PulseAudio timer scheduling ===

If your problem is specific to PulseAudio, you could as a last resort, try to turn off !PulseAudio's timer scheduling. Note that this might consume slightly more power.

To change this, edit the file /etc/pulse/default.pa and change the line that says:
{{{
load-module module-udev-detect
}}}
to
{{{
load-module module-udev-detect tsched=0
}}}

After editing the file, reboot your computer for changes to take effect. 

=== Report a bug ===

We want audio to be working out of the box, without users having to apply fixes manually. So even if the above actually fixes your problem, please also file a bug (also stating the suggested workaround) with this command:
{{{
ubuntu-bug audio
}}}

Thanks!