[linux-audio-user] Real Time Sound Levels readings and comparing

[studio64]

HI All
Is there a Linux way of recording sound from a club or pub/bar using a 
real time analyzer
and then getting an average DB level reading?

I would then need to take another reading later and compare the two.

In the UK there is a lot of new legislation re sound levels from bars 
and clubs
and I would like to offer a service to show them the levels they are 
putting out.

I would need some way of printing the levels out in a document.

This will show that if the clubs has a certain sound level on the dance 
floor it can't be above a certain level at the street.

ie:
75db in the club  may read only 65db in the street, meaning they are not 
causing a noise problem.

I'm using 64studio/Ardour/Jamin  at the moment on debian, but have also 
use the planet on Redhat/Fedora.

I'm sure its all in here somewhere I just need to know what to learn.

Cheers
Bob