Install pavumeter by entering the following commands in the terminal:
sudo apt update sudo apt install pavumeter
Description:
PulseAudio Volume Meter
PulseAudio, previously known as Polypaudio, is a sound server for POSIX and WIN32 systems. It is a drop in replacement for the ESD sound server with much better latency, mixing/re-sampling quality and overall architecture. . A simple volume meter for the PulseAudio sound server.
Homepage: http://0pointer.de/lennart/projects/pavumeter/
Version: 0.9.3-4build2
Section: universe/sound