Sound chattering problem on firefox (opera)

[email protected]:~$ grep VERSION /etc/os-release
VERSION=”20.04.1 LTS (Focal Fossa)”
VERSION_ID=”20.04″
VERSION_CODENAME=focal

When I listen YouTube talk on firefox, sometimes
“I am Tony” has been changed to “I I am Tony” or “I am am Tony”.

Can I solve the sound problem?

The following trials were all in vain.

—-(1)
$ tail -2 /usr/lib/firefox/firefox.sh

exec nice -n 10 $MOZ_LIBDIR/$MOZ_APP_NAME “[email protected]”
fi

—-(2)
$ sudo swapoff -a

—-(3)
$ sudo ip route change default via 192.168.1.1 dev enp8s0 proto dhcp metric 100 initcwnd 10
$ sudo ip route show
default via 192.168.1.1 dev enp8s0 proto dhcp metric 100 initcwnd 10

$ sudo sysctl -w net.ipv4.tcp_slow_start_after_idle=0

—-(4)
$ sudo cpupower frequency-set –governor performance

—-(5)
$ cd /usr/lib/firefox/
$ sudo chmod +s firefox *.so

—-(6)

$ sudo /usr/bin/mkdir /run/cache2
$ sudo /usr/bin/chmod 777 /run/cache2
$ sudo /usr/bin/chown u /run/cache2

$ cd ~/.cache/mozilla/firefox/owaap2lx.default-release
$ mkdir .ORIG
$ mv cache2 .ORIG
$ ln -s /run/cache2 cache2
$ ls -lag cache2
$ firefox

—- (7)
$ ubuntu-drivers devices # nvidia-driver-390 – distro non-free recommended
!! Apply the nvidia-driver-390

BTW, from pyppy linux,

$ sudo dd if=TheFirstUbuntuFocalFossaInstallation.img of=/dev/sda5 #… Only last strategy makes the ubuntu’s sound normally.