Meet.jit.si: Lenovo Thinkpad laptop running Windows 10 (Firefox, Chrome, and Edge): unusable audio

As part of my Jul 6th 6:30PM-8PM EDT meet.jit.si testing conference, a user Rich has reported the following issue:

I connected to the meeting Jitsi URL prior to the meeting using three different
browsers from my Lenovo Thinkpad laptop running Windows 10 (Chrome, Firefox,
and the latest Chrome-based version of Edge). In each case I was able to
successfully join by myself, with my Video and the audio microphone and speaker
testing OK – using a Plantronics USB headset. However, when I tried to connect
to the actual call already in progress with Chrome and Firefox from the same
laptop, video was OK but Audio was totally unusuable – there was a continuing
background pulsing noise and I could not hear anyone else. I also reduced the
video quality to low resolution and still the audio was unusable. I then
connected using Chrome from a desktop machine (with more RAM and faster CPU)
also using Windows 10, and with same Plantronics headset. Initially I got a
similar audio problem but after you muted yourself and then unmuted yourself I
could start hearing folks (but audio quality not great). Again, I tried to
lower video quality but that did not improve the audio. I clicked on one of
icons that appeared to indicate that Internet was having problem in terms of
dropped packets, but I generally have very good Internet and do not have video
or audio problems when using Zoom.

Any suggestions as to how I can help Rich connect to my Jitsi calls?

Do we need more information to debug further?