As new regulations constantly decrease the levels for acceptable noise, it has become increasingly important to minimize the exterior noise level of cars and trucks. As the levels approach what is technologically possible with available techniques, it becomes more important to have as much information about the noise radiating mechanism and the relationship to other mechanical processes in the vehicle. A typical passby measurement will therefore not only be a simple measurement of the maximum sound pressure level, but will include a detailed frequency analysis and order analysis, both as a function of the vehicle speed and position relative to the microphone. Simultaneously the throttle position, engine rpm and vehicle speed is measured and stored with the noise data.
The result is a complete measurement record as a function of the vehicle position, with all relevant information. This can afterwards be examined in detail to identify specific noise sources or resonances to assist in the noise reduction work.