Pass-By (or Drive-By) Noise testing consists of a vehicle being driven past a microphone in acceleration and constant speed tests, on a high quality road surface, and in an open area to avoid sound reflections.
The subsequent sound readings must fall within parameters such as those set by European Directive 2007/45/EC and ISO 362, which set out how much engine and tyre noise produced by passenger and commercial vehicles is acceptable. Given the continued reduction of these noise limits, such testing is extremely important to vehicle and tyre manufacturers, and therefore requires very accurate and consistent measurement of speed and acceleration.
In addition to the vehicle speed and acceleration values, engine speed and throttle application must be logged, and the test is carried out over a prescribed distance as set out in the directive. To achieve the level of distance accuracy required, traditional testing methods require more than one operative and often use several light-barrier units placed at ten metre intervals; or make use of a DGPS Base Station. The former method can be problematic in consistency, as light-barrier triggering can be adversely affected by vehicle body angle or when the vehicle under test has uneven sides - such as a motorcycle. The latter, whilst providing very good positional accuracy, is expensive.
The Racelogic solution uses the VBOX distance measurement with accuracy of 0.05%, so over the 60m a Drive-by Noise Test is conducted this ensures a distance accuracy of 3cm. A single light barrier is used to trigger the start of the test and, being the only one, it can be placed closer to the passing vehicle, ensuring reliability. The VBOX will capture speed, acceleration, throttle position, and engine RPM as the test is performed, and can also record the output from specialist microphones, via Bluetooth radio telemetry, that are placed on the side of the track.
The VBOX system allows for one operative to conduct multiple tests and for each result – including the noise output – to be logged in the VBOX Tools software, greatly reducing the amount of track time required.