Where can I buy a cheap sonometer?

Well that's it, I need to measure street noise, rehearsal room noise, etc, in order to test soundproofing and isolation techniques in the scientific way. For example the level of the noise leaked into my neighbour's bed room before and after the soundproofing. Some links will be appreciated. Thanks. Ed.

I need to buy it in the USA, better in the Miami area. Thanks Ed.

Ed, I had tried to answer this a couple days ago but the site was acting up so I couldn't - Unfortunately a cheap SLM won't do what you want - for one that is sensitive enough to measure low enough sound levels it would cost at least $1000 US - the less expensive ones ($40-50) only measure down to about 50 dB - see this thread http://www.johnlsayers.com/phpBB2/viewtopic.php?t=4285 for more... Steve