ENGINE NOISE TESTING
THE CHALLENGE
Engine noise reduction work includes Acoustic Transfer Function (ATF) determination. Most widely used is the reciprocity method with a high number of free-field microphones. This method is cumbersome and very time consuming and because the setup is difficult to reproduce, the accuracy of the results is limited.
THE SOLUTION
GRAS’ solution is the new 147AX microphone (patent pending) in an optimized design with a unique mounting system and a new form factor. With this microphone the ATF method can be improved significantly: Much greater repeatability and very fast test setup.
And the same microphone can be used in the same test setup for both hot engine and on-road engine testing.
The 147AX will be released in 2019.
Technical Paper: Improving Measurement Procedures for Engine Noise Reduction with Advanced Microphones
Presented by Per Rasmussen, CTO at GRAS Sound & Vibration, at Automotive Testing Expo 2018, Open Technology Forum, October 2018 in Novi, Michigan, USA.
BRAKE NOISE ON-ROAD TESTING
THE CHALLENGE
Due to the rough environment, recording of brake noise in the wheelhouse during on-road testing is very demanding. This generally leads to the use of sub-standard microphones with limited or even unknown acoustic performance. Also, this often requires custom-made and troublesome protection of the microphone.
THE SOLUTION
GRAS’ new solution is the 147EB rugged measurement microphone combined with a special wheelhouse protection kit. It can withstand many thousands of miles of driving in all kinds of weather as well as provide valid acoustic data that it has not been possible to record before.
The 147EB will be released in 2019.
POWERTRAIN / EXHAUST NOISE / ROAD NOISE / PASS-BY / BRAKE DYNAMOMETER TESTING
THE CHALLENGE
A common challenge to all acoustic NVH testing is the need for valid data. Typically, standard ½” microphones are found in most test setups today. However, the setups for these applications face serious challenges: High temperatures, drops, shocks, dust, oil and water.
THE SOLUTION
GRAS’ solution is the 146AE – the world’s first CCP free-field measurement microphone set specifically designed to operate reliably in many different harsh NVH test setups. By introducing a rugged measurement microphone, designed to withstand harsh environments and fully compatible with the current microphones used today, it is possible to use the same sensor in a large number of different test setups.
The 146AE is a new standard, which provides valid acoustic data and ruggedness in one package.