The Muffled Output
Ubuntu utilizes PulseAudio (or PipeWire in newer releases) as its primary sound server. By default, the system tries to protect your speakers and your hearing by preventing extreme audio clipping. If you push a media player’s volume past 100% (a feature called “Over-Amplification” in the GNOME tweak tool), or if a sudden, extremely loud notification sound plays, the sound daemon may automatically step in and aggressively lower the master volume slider to compensate. While safe, this “auto-ducking” or volume normalization ruins the dynamic range of movies and forces you to constantly manually push the volume back up.
Disabling Audio Normalization
To maintain consistent audio levels and stop Ubuntu from automatically lowering your master volume in response to loud peaks, you must disable flat volumes in the PulseAudio configuration.
You need to edit the sound daemon’s configuration file via the terminal. Open your terminal by pressing Ctrl+Alt+T. Type sudo nano /etc/pulse/daemon.conf and press Enter (provide your password). Scroll down through the text file until you find a line that says ; flat-volumes = yes. (The semicolon means the line is commented out and using the default “yes” behavior). You need to delete the semicolon to activate the rule, and change “yes” to “no”. The line should look exactly like this: flat-volumes = no. Press Ctrl+O then Enter to save, and Ctrl+X to exit. Finally, restart the sound server by typing pulseaudio -k (it will immediately restart itself) or simply reboot your computer. Your volume slider will now remain exactly where you put it.