separate mic/headphone volume control

[Newtwin]

I installed Ubunut 12.04 64 bit, and it seems I can not adjust volume separately for headphones and laptop speakers.
If I plug my headphones in, I can hear sound through my headphones AND my speakers. I can not turn of the speakers, so I can listen music, in the same room where someone else is watching tv.
In system settings - sound I can neither alter this setting as needed.

Anyone an idea how to change of what software to install that would make this possible?
(Hardware is HOP Pavilion dv7)

[wyliecoyoteuk]

Install a mixer program that will allow you to control the various outputs and inputs.
There are quite a few in the software centre

[cybrsaylr]

Insall PulseAudio Volume Control which works great for that.