[LAU] 'morse code' picked up by the speakers

[jonetsu]

Recently the speakers (Yamaha HS5) are 'picking up' 'morse code' (for
lack of better description).  I don't think this goes into any
recording (haven't checked yet).  So, erratically, maybe a few times
per hour, the speakers will put out a short 'morse code' type of beeps,
whether there is music playing or not.  It could be at total idling
time.  They never did that before.

My question is, what is the source of these short beeps ?  Even if they
are not recorded they can be disturbing when improvising or in a quiet
piece.