NO COURT IN THE LAND WILL ACCEPT anything that has not been home office sanctioned, as evidence, the real reason why noise tests are not being conducted is due to cost, plod legally has to undergo training, with yearly refresher course to operate ANY evidence gathering device, or a chav could get it kicked out.
It's very subjective noise is, the meter reading can differ enormously from what the human ear hears, as a HUGE amount has to do with frequency, but pissing off the neighbours and plod with driving like a dick can get you nicked for EXCESSIVE NOISE AT WELL UNDER THE LIMIT OF NOISE ALLOWED, you can also get done for FURIOUS DRIVING.
tabetha