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

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