Measurement microphones for automotive NVH testing

In the automotive industry, engine noise reduction incudes Acoustic Transfer Function (ATF) determination. The reciprocity method with a high number of free-field microphones is most widely used but can be cumbersome and time consuming. GRAS says that, because set up is difficult to reproduce, the accuracy of the results are limited.

GRAS new 147AX CCP Rugged Pressure Microphone has been developed in conjunction with Volvo Cars in Sweden. It is a surface microphone optimised for highly efficient cold and hot engine noise testing and repeatable measurements. Plus, it introduces a special form factor which, together with a special mounting system and new measurement methods developed with Volvo Cars, ensures accurate, reliable data.

Due to the rough environment, recording of brake noise in the wheelhouse during on road testing is very demanding. This can lead to use of sub-standard microphones with limited or even unknown acoustic performances. As a result, it often requires custom-made and troublesome protection of the microphone

The new GRAS 147EB CCP Extra-Rugged Microphone Set is a robust microphone which has been specially designed and optimised for on-road brake noise testing. It has a three-layer protection of the diaphragm and has been tested with Volkswagen in Germany where it has undergone more than 10,000 miles of on-road testing on all surfaces and in all weather conditions.

GRAS product manager Jan Hansen, comments: “GRAS has developed new products targeted at specific applications that revolutionise existing test methods and significantly reduce rigging up time. We have tried to address the most common challenges as experienced by industry professionals within each application area by way of mapping these from start to finish.”

With the well proven, popular 146AE ½in CCP Free-field Microphone, GRAS now a comprehensive range of microphones for all automotive NVH applications.

The new GRAS products complete a full portfolio of microphones covering all application areas within automotive NVH testing:

•  147AX - cold and hot engine noise testing

•  147EB - on-road brake noise testing

•  146AE - testing pass-by noise, road noise, buzz, squeak and rattle noise as well as power train noise.