The Pulse Audio equalizer gives you the opportunity to set up and enable a system-wide equalizer in order to help you tune all of the sounds in a certain preset. If you’re using Ubuntu, you can install this utility through a third party repository. Enter the following commands to do so:
sudo add-apt-repository ppa:nilarimogard/webupd8 sudo apt-get update sudo apt-get install pulseaudio-equalizer
You may choose a preset from the presets list on the right, or set the levels on your own. When the ‘EQ Enabled’ box is ticked, the equalizer is active and all sounds from all streams are affected by the its settings.