[deanhills]

Thanks very much for your quality post @Hidden Refuge.  I've got a Dell Optiplex desktop computer and thought it was a beep I heard, but maybe it is something else?  It's a single one-off beep that only happens very occasionally, like maybe once a day, or alternate day.  I checked up the beep codes for Dell below, however can't figure out where the beep fits in the codes.  Maybe it's something else?
http://www.dell.com/support/article/za/e...pc?lang=en

I suspect that it could be something to do with my RAM?  As at end of 2016 when I reformatted the hard disk of the computer I got a technician to add additional RAM.  Maybe the new RAM is not completely in sync - like it is OK, but maybe it causes a beep very occasionally?

Note later:  Just noticed this at the bottom of the Dell article - my Dell Optiplex is 9010 - so not sure whether the note applies to it as my Optiplex only makes a very occasional single beep?

Note: Starting from the D4 generation of OptiPlex models onwards (i.e. 7010/9010/9010 AIO), the beep codes will be eliminated, replaced by a single memory error pattern. Now only no memory failure conditions generate the beep code, the beep pattern is 1-3-2 (1 beep, then 3 beeps, then 2 beeps). This beep code tells you that the computer encountered a memory problem. The new beep codes emit only memory failure symptoms. Occasionally, reseating the memory modules may fix the beep code errors.