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Originally Posted by The Producer
this is a good time for an ELI5
How do sound meters work? how does sound work? I'm pretty mechanically minded, but I have no idea about acoustics. 128kb and 256kb Mp3's sounded the same to me in winAMP
If the meter is sitting on the ground like in the pic above, adn the car is off - can it give you the reading of ambient sound? like say 30db of traffic and wind and other shit?
The MVA states that 83db is the limit for exhaust (i think). I've heard it explained here that it's supposed to be in a quiet controlled environment (like a testing station).
Do the VPD's sound meters take a "tare" sound level? Like I would zero out a scale based on the container weight before i measure its contents? is the reading calculated by subtracting the ambient sound level from the meter's result? do sound levels stack up like that?
I'm sure google can tell me this, but I'll bet there's an audio engineer on RS who can explain it better.
we all know you can't dispute VI's, and we've discussed that there is total ambiguity about how the meter is used, but I'd certainly be disputing the "excessive sound" tickets (and 3 points)
We have a meter out at the autox pad, I've never played with it. I think next time I might.
Kind of a theadjack , but I'm interested and would like to be educated if I run into one of the above situations so I can document it correctly.
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Someone on that same thread on Facebook posted a graph showing that every time you double the distance of the meter from the source of the sound it drops another 6dB... so if it's like 12" away like in that photo and measuring 90dB if he moved it to 2 feet away it would theoretically drop to 84dB... and likewise the exhaust would not be illegal to anyone in the vicinity who would be like 20+ feet from the car at any given time.
In short, the testing procedure is everything. A totally legal car can easily be made illegal depending where the microphone is placed.