General Motors shares NVH testing secrets behind all-new Astra


General Motors has revealed details of its NVH program for the new Astra. Engineers led by Bernd Justen, vehicle performance manager for Vauxhall/Opel compact class cars, tested the Astra in the company’s acoustic lab in Rüsselsheim, Germany. The vehicle was also tested on the comfort and noise evaluation track at the company’s Dudenhofen test center in Germany.

Reducing engine noise was of particular importance. The Astra was also tested against a list of other requirements, as Justen explained, “Apart from the appropriate sound of the engine or rolling noise, this includes the sound made by the closing of a door or the clicking of the indicator. We initially checked in simulation the basic settings, and based on this we continued with the optimization process until the Astra met our noise requirements.”

The Astra was also driven on a rolling road inside the acoustic chamber and tested in various scenarios under consistent conditions. These tests considered idle behavior, the start/stop function and driving under part or full engine load. A typical procedure for example, is ‘full-load, rev-up’ in third gear.

Meanwhile, dummy heads were used to confirm the exemplary noise level. “There are highly sensitive microphones fitted in the ears of dummy heads. They enable us to record and replay noises in the same way that a real human would perceive them,” Justen said.

This enables stereo recording and replay, as well as differentiation between the upward and downward direction of noise, making the dummy’s hearing virtually three-dimensional.

To achieve the desired occupant sound level, a binaural transfer path analysis and synthesis was conducted using so-called binaural measurements. This enables a distinction between airborne and structure-borne noise source paths.

December 7, 2015


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John joined UKi Media & Events in 2012 and has worked across a range of B2B titles within the company's automotive, marine and entertainment divisions. Currently editor of Automotive Testing Technology International, Crash Test Technology International and Electric & Hybrid Marine Technology International, John co-ordinates the day-the-day operations of each magazine, from commissioning and writing to editing and signing-off, as well managing web content. Aside from the magazines, John also serves as co-chairman of the annual Electric & Hybrid Marine Awards and can be found sniffing out stories throughout the halls of several of UKI's industry-leading expo events.

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