[PLUG] Audio hum when playing Blu-ray movie

[John Jason Jordan]

On Wed, 21 Jun 2017 15:45:29 -0700
Denis Heidtmann <denis.heidtmann at gmail.com> dijo:

>I do not know much about what you describe, but you could answer the
>frequency issue by recording the sound into Audacity on the laptop.
>(Assuming you do not have a 'scope.)
>
>Is there a chance that the connections which produce the hum include
>two different AC powered devices with a (not quite) common ground?

Since my original message I have discovered that the hum goes away
on the desktop if I turn off the right channel in Pulseaudio (the movie
has only stereo, not 5.1). I have no idea what this means.

I also compared all the settings in Pulseaudio on the laptop to the
settings on the desktop. I didn't see any differences, except that
some are different because the two computers have different audio
processors, plus I don't know what all the settings mean.

As for the frequency, I note that it goes up and down when I change
settings in Pulseaudio. Even at its lowest it is higher than 60 Hz, so
I doubt very much that it is related to household AC power. Besides, AC
power might affect the stereo or the audio cables connecting to it, but
the computer? After going through the power supply and its rectifiers?
I could check it out in Audacity, but I doubt that doing so would
reveal much.