I hope the mucrophones are able to focus in to measure a single vehicle. Not a very easy parameter as background noise can add to a single source. Cameras/radar for speed can be focused to enable more accurate targeting.
The IVA noise test for kitcars etc involves a specific set-up to measure nouse of the car. Basically mics at measured points round the car when it is in an open area not enclosed. I assume it is similar to homologation noise testing. Parabolic dish mics? Calibration and accuracy are paramount for credible evidence for legal action. This is what cameras for speed need and are then approved.
For noise, will a triggering start a process of locating the vehicle, a letter to attend a test station sent, or someone turning up at the house to inspect rather than an automated NIP legal process?
The crux would likely be the capability of the device to ensure single fehicle ID.
