try running these commands (via alt+f2 or terminal):

volume to 150%:

pactl set-sink-volume 0 150%

to return the volume to 100% simply:

pactl set-sink-volume 0 100%

(video demonstration of those commands here)

Note that the argument after set-sink-volume specifies your sound device. If you have hdmi you will likely have 2 devices and you need to check for your device id using alsamixer or pacmd list-sinks or even pactl list sinks.

If it doesn't work, try this script.

If it works, manually set a keyboard shortcut for these commands through the application 'keyboard shortcuts' (on ubuntu 11.04: key 'super' -> type 'keyboard shortcuts' -> button 'add').

The command pactl belongs to the package "pulseaudio-utils' to install it use the command:

sudo apt-get install pulseaudio-utils

The maximal possible volume level we can obtain from sliding the volume control to more than 100% is approx. 153% above the normal peak limit. Provided we had set the ALSA volume with alsamixer to 100 these 100% are the level above which audio will be clipped or distorted. This also will happen when amplifying to 153% with the slider.

Nevertheless is is possible to further increase this level by setting the sink level using the follwing command in a terminal:

pacmd set-sink-volume <sink> <value>

Replace <sink> with your sink name or sink index as given from:

pacmd list-sinks

The lower limit for <value> obviously is 0, a linear volume of 100% is a value of 65536, anything higher will be further amplified. A value of 512000 will thus lead to an overamplification of 781%.

This is a very crude method to amplify sound output of varying level as overamplifying will lead not only to clipping and ugly distortion but may also damage your speakers.

Therefore it would be a better way to normalize your audio output. See the following question on how to do this with pulseaudio:

• Automatically adjust the volume based on content?