Ever wonder what automakers go through in order to build vehicles that perform smoothly and quietly? Well, we’ve shown you how GM’s German subsidiary, Opel, makes sure the Astra is “crackle free“, and now we’re going to tell you all about its near-silent performance.
Opel engineers ensure that the new Astra meets demanding noise requirements by testing it thoroughly at the Opel acoustic lab in Rüsselsheim. All new models going through development must go through this lab, as well as the comfort and noise evaluation track at the Opel Test Center in Rodgau-Dudenhofen.
The noise and vibration from the 1.0L three-cylinder and 1.4L four-cylinder Ecotec motors are measured during a procedure called the ‘full-load, rev-up’ which is a wide-open-throttle third gear pull. Both engines pass the test “with flying colors” while always remaining within the pre-defined tolerance curve for cabin noise. According to Opel, the implemented measures to reduce the noise level include splitting the oil pan, noise protecting the integration of the cylinder head into the exhaust manifold, designing a sound-absorbing cam cover, decoupling the high-pressure injection valves and trimming the timing chain for quiet concentricity.
The Opel Astra is also “dummy head” tested. Bernd Justen, Vehicle Performance Manager for compact class cars, explains what this means:
“Our dummy heads confirm the exemplary noise level… There are highly sensitive microphones fitted in the ears of dummy heads too. They allow us to record and replay noises in the same way that a ‘real’ human would perceive them. This allows us to identify and analyze the different sound source.”
By using a noise transfer path model, engineers can identify, for example, which screw needs to be turned to achieve the “agreed target value” — first virtually and then in reality. If both cases show improved results, then the Astra is one step closer to production readiness.
Isn’t science marvelous?