the sound is not as loud as with windows i have a sony vio pcv-a31l

You have tried alsamixer and maxed everything?

yes

I have a sony vaio too and I have the same issue with the sound volume.

I have an Acer Extensa 4630z laptop, it has a dual boot of Windows XP SP3 and Ubuntu 8.10 and the sound in Windows is much louder than Ubuntu. The Master and PCM in Volume Control are at maximum, I didn't find a solution and I don't think there is one as I found in this post :
http://thevistaforums.com/index.php?s=a857b9fb84ea97c641450419c29934a6&showtopic=42260&pid=291171&st=0&#entry291171

It says : "Yes linux has a lower max volume compared to windows. No way around it. This was the same since OSS and the switch to ALSA just made it worse."

With Ubuntu 8.10, I think PulseAudio is use by default, but on the tracker of bugs of PulseAudio I didn't find any bug relating to this issue unfortunately.

I found this at another site and it worked for me:

(http://ubuntuforums.org/archive/index.php/t-346523.html)

Right click on the speaker on your main panel.

Select preferences

For me, anyway, select the headphone (or 'Front') item in the list (I had it on Master). AMAZING! I nearly blew my speakers!

If you "Open the volume control", you can select multiple sources and PCM-2 seems to be the magic slide.

Anyway, once you crank out the various inputs/outputs. Just make sure the headphone slide is up.

Maybe this is a bug? The Master slide has no effect whereas the headphone output works like a master.

Hope this helps.