Bill,

The "buzz" is most likely because your rx.py has been configured to send wireshark (UDP) data but the vocoder hasn't been turned on with the "-V" option.  Check and/or post your command line options.

Here are mine.  Obviously some are specific to my setup, but everything after "-S 960000" should be good for you too
./rx.py --args "rtl=0" --gains 'lna:36' -f 773.84375e6 -S 960000 -T trunk.tsv -q 0 -V -2 -U 2> stderr.2