!NEW! All-New Opel Astra in the Acoustic Lab

• Dynamic, smooth, comfortable: New engines for pleasant sound
• No din: “Dummy heads” as sensitive as the human hearing

In the acoustic lab: New Opel Astra is positioned in the center of the room and is surrounded by numerous microphones.

Silence. It is so quiet in the unusual looking room that you could literally hear a pin drop. The new Opel Astra is positioned in the center of the room and is surrounded by numerous microphones. Is the engine sound of the new compact class star being recorded for the next advertising campaign? Not quite. When the Opel Astra arrives in the acoustic lab, it is still in the final phase of being made ready for series production. The engineers around Bernd Justen are partly responsible for making sure that the new Astra really is a quantum leap. They ensure that the compact class car meets the demanding noise requirements and test the Astra thoroughly in the Opel acoustic lab in Rüsselsheim. Apart from being tested on the comfort and noise evaluation track at the Opel Test Center in Rodgau-Dudenhofen, all new models developed by the carmaker have to come here for final testing.

Meets all noise requirements: All-New Opel Astra in the acoustic lab in Rüsselsheim. 

Noise & vibration: All good under the Opel Astra hood

The dynamic sound of the vehicle while simultaneously delivering excellent running smoothness was always high on the list of specifications of the new Opel Astra. Primarily, the turbo-charged gasoline and diesel engines of the latest generation that power the Opel Astra and make its athletic appearance audible ensure this. “That is only one aspect we check in the acoustic lab,” explains Bernd Justen, Vehicle Performance Manager for compact class cars. Moreover, the Astra is put through an extensive and precisely defined requirements list. “Apart from the appropriate sound of the engine or rolling noise, this includes the sound made by closing a door or the clicking of the indicator. We initially check the simulation-based basic settings. Based on this we keep on working until the Astra meets our noise requirements.”

On the roller test bench: The engines offer a pleasant and dynamic sound experience – and reduces noise levels in the cabin.

The walls and the ceiling of the lab are completely soundproof thanks to noise absorbing materials. During testing, the Opel Astra is driven on large floor rollers, which produce the same resistance the car would experience on the road from wind and rolling friction. “This enables driving with road-like loads. It does not depend on the weather and we can test various scenarios under consistent conditions,” said Justen. These tests include idle behavior, the Start/Stop function and driving under part or full engine load for example. The highly sensitive microphones record all noises so they can be analyzed afterwards.

Meets all noise requirements: All-New Opel Astra in the acoustic lab in Rüsselsheim.

A typical procedure on the roller test bench is ‘full-load, rev-up’ in third gear – a demanding test that the all-new 1.4 ECOTEC Direct Injection Turbo, a four-cylinder Opel unit from the same engine family as the innovative one-liter, three-cylinder engine, passes with flying colors while always remaining within the pre-defined tolerance curve for cabin noise. Just like the three-cylinder engine, the 92 kW/125 hp or 110 kW/150 hp unit was developed with setting new standards in noise and vibration characteristics in mind (fuel consumption combined: 5.5-4.9 l/100 km, CO2 emissions combined: 128-114 g/km). The outstanding refinement was achieved through the noise-optimized engine block design. The implemented measures to reduce the noise level included 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 test bench quickly reveals that the engineers did an outstanding job: The engines offer a pleasant and dynamic sound experience – and reduces noise levels in the cabin.

“Dummy head” tested: Pleasant sound in the Opel Astra cabin

“Our dummy heads confirm the exemplary noise level,” explains Justen, referring to the weird looking figures in the Opel Astra cabin that are reminiscent of mannequins. Plastic effigies of the human head and shoulder area that possess a perfect replica of all acoustically relevant elements of the human outer ear adorn the seats. “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 enables stereo recording and replaying, as well as differentiation between the upward and downward direction of noise, making the dummy’s hearing virtually three-dimensional.

Dummy head: Plastic effigies of the human head and shoulder area that possess a perfect replica of all acoustically relevant elements of the human outer ear are used in the acoustic la

To achieve the desired vehicle sound that is pleasant for occupants, a binaural transfer path analysis and synthesis is conducted using so-called binaural measurements. This enables a distinction between airborne and structure-borne noise source paths. “This allows us to identify and analyze the different sound sources,” explains Justen. 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 produce satisfactory results, the Astra has taken its next hurdle on the way to production readiness.

!NEW! The Reliable Opel: Zafira MPV Cruises to 500,000 km

• Zafira A MPV clocks 500,000 km in front of the Adam Opel Haus
• Opel Group CEO Dr. Karl-Thomas Neumann welcomes owner

Tough call: Opel Zafira driver Andreas Schild (right) and Opel CEO Dr. Karl-Thomas Neumann (left) debate whether he should swap his trusty red Opel Zafira for a New Opel Zafira Tourer.

The timing was perfect, the last stretch planned in every detail: When reaching the forecourt of the Adam Opel Haus the speedometer of the Zafira turned over to 500,000 km. After 12 years of loyal service to its owner Andreas Schild from Frankfurt, both the car and the driver received their just reward. Opel Group CEO Dr. Karl-Thomas Neumann welcomed Schild and his Zafira in front of the Adam Opel Haus.

Perfect timing: Opel Zafira owner Andreas Schild timed his visit to the Adam Opel Haus to perfection, reaching 500,000 km in front of the Opel HQ in Rüsselsheim.

Schild’s Zafira is a 2.2 liter DTi built in 2002 with 125 hp with Selection Executive trim. What makes the car special is that despite reaching half a million kilometers only very few parts, apart from the usual wear parts such as brake disks or brake pads, have been have been changed: the rear muffler, two suspension struts (without the shock absorbers) along with the power steering pump. All other parts are still the originals.

Polished appearance: Andreas Schild had the Opel Zafira washed and polished to ensure that it would truly shine on its big day.

“Apart from being used as business vehicle on a daily basis, the flexible van is also frequently seen on trips to southern Europe to buy wines and Mediterranean delicacies,” said Schild. “Once I loaded 495 wine bottles and I never had the feeling that I was asking too much of the car.”

“Mr. Schild’s Opel Zafira is an example of the core values of our brand: German engineering and precision combined with high user value are essential components of our brand DNA. Current studies such as the J.D. Power Study Germany 2014, in which our Meriva had the highest customer satisfaction in its sector, underline this,” said the Opel CEO. “The idea behind the excellent Flex7 seating system swung my decision when I bought the car. This system is a real piece of engineering ingenuity,” added Schild.

“When did you buy it?”: Opel CEO Dr. Karl-Thomas Neumann (right) finds is pleasantly surprised by the fact that Andreas Schild (left) has been using his Opel Zafira on a daily basis for twelve years and has amassed 500,000 km.

The owner of a Frankfurt-based event agency has always been a huge fan of the traditional brand. His first car was a 1965 Record 1900 L that his uncle bought him after he passed his driving test in 1978. He also had other Opels such as a Kadett, an Omega and a further Zafira.

Schild is especially amused by the reaction of his friends and family when he continues to roll up in his flexible seven-seater. They always ask the same question. What ? That car still works ?