A Practical Approach for Pass by Noise Testing of a Car Simulated in a Semi- Anechoic Chamber

In-door simulation of Pass By Noise [PBN] Testing of a car was successfully attempted on a chassis dynamometer in a full-scale Vehicle Semi-Anechoic Chamber [VSAC].

The work has a practical approach for quick testing of vehicles to be submitted for certification. It has 3 parts:

1. 1
   Confirmation of overall Indoor PBN Testing as per ISO 362-1:2007 (E)
2. 2
   Correlation of the PBN-results obtained on the Track with those in the VSAC as per both Method A and [proposed] Method B based on vehicle-acceleration depending on Power to Mass Ratio of the Test-vehicle
3. 3
   Use of this In-door simulation for quick evaluation of design modifications of the vehicle to meet its PBN Limit with a safe margin

Optimum no. of microphones was sought out in VSAC to reduce the set-up time without sacrificing accuracy of the results. Dyno-roller / tyre radiated noise need be reduced to have the close correlation with the Track results. There was almost the same trend of influence of changes in dominant design parameters on the vehicle PBN as measured in the VSAC and on the Track. Measured Acoustic Transfer Functions [ATFs] between the source and microphone at 7.5m were used to determine the source contributions to the maximum PBN of the vehicle.