The noise seems to becoming from my computer and printer across the room. I
notice no other loud steady noise level on any other frequencies. Is the
frequency of 11955kHz some harmonic of an RF signal being produced by the
computer and/or printer. The adjacent frequencies are free of this noise.
I've only started monitoring this frequency four months ago. I assume that
the noise could have always been there. I'll listen again when all of the
computers, printers, TVs, etc. are turned off for the night and will report
back tomorrow.