Sound Adjustment is a lite add-on that let you easily adjust few sound settings from toolbar popup.
Currently, there are three options to adjust. The first one is volume, the second is balance and the last one is amplify. All these settings are stored for the current tab only. Once you change tabs, settings are reset to defaults.
The volume setting is from 0 to 100 units. Balance variable changes from (-100%) to (+100%), where -100% is the left speaker only and (+100%) is the right one. Any value between these numbers divides the sound output between speakers proportionally. The last setting is for the amplify option, where it amplifies the output sound from 100% to 500%. 100% is the original level and 500% makes the output sound 5 times louder than the normal settings.
Note: this add-on only works for HTML5 audio and video elements. Moreover, currently the add-on does not work for media elements embedded in frames.
If you have a feature request or found a bug to report, please fill the bug report form in the add-on's homepage (https://mybrowseraddon.com/sound-adjustment.html).