Audacity suffers from buffer underruns when recording, then it distorts the audio and locks up

 The mistake repeats itself to infinity (and beyond):

ALSA lib pcm.c:7843:(snd_pcm_recover) underrun occurred

underrun occurred (bug en Launchpad).  Temporary solution:

alias audacity='env PULSE_LATENCY_MSEC=30 /usr/bin/audacity'
audacity

underrun occurred:
sudo sed -i 's/^Exec=.*/Exec=env PULSE_LATENCY_MSEC=30 audacity %U/' /usr/share/applications/audacity.desktop
echo "alias audacity='env PULSE_LATENCY_MSEC=30 /usr/bin/audacity'" >> ~/.bashrc