The Audio Normalizer
Ubuntu uses PulseAudio (or PipeWire in newer versions) to manage system sound. Sometimes, when using specific communication apps like Skype, Zoom, or even some web browsers, you might notice your system volume slider moving entirely on its own. You turn the music up, and a few seconds later, Ubuntu automatically turns it back down. This occurs because these applications are granted permission to dynamically adjust your microphone gain and output volume (often called Automatic Gain Control or AGC) in an attempt to “normalize” the audio levels during a call. Unfortunately, this often results in the OS fighting your manual volume adjustments.
Locking the Volume Levels
To retain manual control over your audio and stop Ubuntu from automatically changing the volume based on application requests, you must disable the application’s ability to manipulate the master mixer.
The most effective way to stop this is to address the specific application causing the issue. For example, if it happens during Zoom calls, open Zoom’s audio settings and uncheck “Automatically adjust microphone volume.” However, to force a system-wide block in PulseAudio, you need to edit its configuration file. Open a terminal (Ctrl+Alt+T) and type nano ~/.config/pulse/default.pa (if the file doesn’t exist, you may need to copy it from `/etc/pulse/default.pa` first). Add the following line to the end of the file: load-module module-role-cork. This module intercepts applications trying to duck or adjust global volumes based on their specific “role” (like ‘phone’ or ‘video’). Save the file (Ctrl+O) and restart PulseAudio by typing pulseaudio -k.