Page 1     |     Page 2     |     Page 3

Unwanted automobile noise and vibration irritates drivers as much as fingernails scrapping a chalkboard.
by Kami Buchholz, Detroit Editor

Scanning laser vibrometer, one tool with DuPont Automotive NVH lab. Sika Automotive acoustic baffle.

Engineering a pleasant-sounding, smooth-riding vehicle means evaluating material choices from a noise/vibration/harshness (NVH) perspective, designing systems to squelch NVH influencers like wind and road noise as well as matching customers' NVH expectations. "NVH is one of the top things we're constantly thinking about," says DaimlerChrysler's Peter Gladysz, a Senior Manager in vehicle development and synthesis. "It's as relevant as performance, handling, and overall styling."

Sources of ugly noise emanating from the powertrain, the roadway, and the wind impacted design/engineering cues on Neon 2000 (sold as Plymouth Neon, Dodge Neon and Chrysler Neon). "Daimler- Chrysler's NVH lab works on all platforms simultaneously, so if anything can be utilized cross-platform — like going to a spiral cut antenna to stop whistle noise — it spreads throughout the product line-up," Gladysz explains. (The spiral cut antenna first appeared on Neon 1999.)

Neon 2000 NVH attributes include:

• A higher volume muffler and an exhaust flex joint to make engine operation quieter.
• A four-point engine mount system to reduce steering wheel vibration at idle speed.
• Stiffer suspension crossmembers and control arms to minimize the resonance from powertrain vibrations.
• Full frame doors (replacing glass roll-up side windows) to form a tight-fitting body seal/noise barrier.
• All-season single ply tires (replacing previous Neon's two-ply tires) to dampen road noise and beef up fuel economy.
• Moving front windshield 76 mm (3 in) farther forward to calm errant wind noise.
• Adding expandable foam baffles inside the A, B, and C pillars as well as in the fore and aft frame rail to cause a drop in decibels.

"The foam baffles expand to fill up the body cavities as the vehicle goes through the e-coat bake process in temperatures of 149°C plus," says Gladysz. Sika Automotive developed and supplied the one dozen foam baffles used on the new four-door Neon. In a typical automotive application, between six and 12 baffles — each expanding three to 20 times pre-bake size — essentially impede noise, water, and dust entrance.

One of the real world simulation chambers at Sika Automotive features a hemi-anechoic chassis dynamometer. "The unique aspect of this chamber is it provides for up to 97 km/h (60 mph) wind. It's not a wind tunnel, but it does generate wind loading at appropriate frequencies. We can also synchronize the wind speed to vehicle speed," explains Phil Weber, Sika Automotive's Manager of Technical Services.

Test rooms feature a suite of anechoic and reverberant chambers for test and development of acoustic materials and applications; a materials testings lab; a sound quality lab and adjoining jury evaluation room for playback of collected vehicle noise measurements; a quiet room with bedplate and carbon monoxide extraction for modal analysis and other structural testing; a full-size body-in-white bake oven for simulation of production bake processes; and a computer room for design and analysis of acoustic, bonding, and sealing applications.

Having a dedicated NVH laboratory is of growing importance to suppliers. "Some suppliers are differentiating themselves with NVH (labs), and in other cases it's expected, so why not make necessity a virtue. For full service suppliers, the new challenge is the difficult task of managing fit and function pieces as well as the NVH piece," says Peter Greer, Principal Automotive Consultant for A.T. Kearney in Southfield, MI.

Vibracoustic North America, an independent wholly owned subsidiary of Freudenberg-NOK, has opened a new noise and vibration testing/product development/headquarters in Plymouth, MI. The $7 million center has counterpart NVH lab operations in Europe and Asia. "With the ever-increasing importance of vehicle NVH, our customers are looking for global suppliers with leading-edge technology, a broad portfolio and complete regional capabilities that are consistent everywhere in the world," notes Mehdi Ilkhani-Pour, President of Vibracoustic North America and former president of Freudenberg-NOK's Automotive Vibration Division.