After an update some months ago, my laptop has begun making a low, repeated clicking sound every few seconds. It is not being generated through the regular sound system, as altering the volume and even muting the sound does not make any difference. My regular audio works fine, by the way, so I am guessing this is some sort of PC speaker, since I cannot hear the click when I listen through regular headphones.

Strangely, when I open the sound settings dialog the click magically disappears. I don't need to change any settings; if I simply leave the dialog open in the background then the problem disappears.

Any ideas what this could be?
I am running regular Ubuntu 12.04, and this is the output from lspci -v | grep -A7 -i "audio":

00:1b.0 Audio device: Intel Corporation N10/ICH 7 Family High Definition Audio Controller (rev 02)
    Subsystem: Acer Incorporated [ALI] Device 0349
    Flags: bus master, fast devsel, latency 0, IRQ 44
    Memory at 54200000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: <access denied>
    Kernel driver in use: snd_hda_intel
    Kernel modules: snd-hda-intel