The LMS Test.Lab Interior Pass-by Noise solution is a popular testing method to simulate pass-by noise using a roller bench in a semi-anechoic chamber. Primarily a lab-based engineering tool, this interior pass-by noise solution supports pass-by noise standards and brings numerous advantages to the testing process.
To start, test engineers are not dependent on weather conditions and this increases productivity and keeps the testing process right on schedule.
Working in a controlled lab environment facilitates the testing process as a whole and makes the run and re-run processes associated with vehicle modifications easy to reproduce with 100% reliability. Pass-by noise engineers find that LMS Test.Lab Interior Pass-By Noise is an ideal method for troubleshooting tough issues and finding solutions quickly.
Designed for one-person operation, the workbook based solution guides the user through the process step-by-step from primary data acquisition all the way to customized reporting at a push of a button. The software calculates the virtual vehicle position based on the provided speed from the dyno. From this information, the overall sound pressure level (OAL) is calculated as a function of position - just like an exterior pass-by noise test.
The user can select from two methods to calculate the OAL. The first method is based upon the energy measured at each microphone location. The second method synthesizes a time signal based upon all the measured microphones. This time signal is equivalent to a time signal acquired from external pass-by noise measured microphones without the Doppler shift. Users can listen to this synthesized time signal as well as use it for OAL-level calculators and order calculations amongst others. Since the vehicle is not moving, the user can measure additional signals on the vehicle as well. This gives a better correlation analysis using the additional measurements and the far-field pass-by noise measurements, so that the pass-by noise engineer gains more insight into what components are contributing most.
By combining the in-room pass-by noise solution with other LMS engineering solutions for sound source localization and source ranking, the in-room pass-by noise solution can drastically reduce development times.
LMS engineering consultants substantially improved the interior and pass-by noise on several new Jiangling Motor Corporation (JMC) vehicles for the Chinese market. JMC needed to reduce noise to meet government regulations and to comply with market expectations. LMS engineers optimized the interior trim of the vehicle, improving the articulation index by 30% with only a 3 kilogram increase in weight. 
