Today’s automotive engineers are on an unending quest to make vehicle interiors quieter and more comfortable. In the auto industry, this translates to reductions in noise, vibration and harshness, or NVH.
Tests show noise is transmitted through the vehicle’s glazing and comes from several sources:
• Air-pressure fluctuations against the windshield at highway speeds
• Air impinging on the edges of the vehicle’s body panels
• Other vehicles and environmental noise
• Road noise and vibration; this is also transmitted through the body structure.
One way to reduce noise is to increase the thickness of the glass. This provides marginal noise reduction and adds weight to the vehicle. This decision will also impact the run channel and overall packaging space if the intended use is a door. The complete packaging envelope may change. A new power unit may be needed to accommodate the added weight. A windscreen is better addressed by an asymmetrical application with an acoustic graded PVB.
More recently, PVB suppliers have developed vinyl with improved acoustic-damping qualities. These new interlayers are particularly efficient in the 1,500 Hz to 5,000 Hz frequency range.
The decibel reduction typically is 2-3 dB overall. Although not large, it results in a quieter vehicle interior that allows people to converse without shouting.
Acoustic vinyl also enables vehicle designers to decrease the thickness of the windshield without negatively affecting noise levels. This is particularly important as automotive engineers try to shave weight off vehicles to make them more fuel efficient. Acoustic vinyl windshields meet all of the same federal safety specs as regular vinyl.
Acoustic vinyl is also suitable for use in sidelites to further improve interior noise levels. Other benefits include:
• Security or theft deterrence. It takes longer to break through a laminated glass window, therefore reducing “smash and grab” theft.
• Improved health. Laminated glass allows for lower ultraviolet light transmittance, especially beneficial to those with melanoma.
• Interior protection. Lower UV transmittance helps preserve vehicle interiors and slow color fading.
• Vehicle weight reduction. The vinyl interlayer’s lower density allows vehicle designers to maintain the same overall window thickness while reducing the weight of the window compared to monolithic tempered glass.
The main downside to the use of acoustic vinyl is its cost. However, the difference in cost between acoustic vinyl and regular PVB will likely diminish as volumes increase. There are 18 vehicle makes and 40-plus models sold in the United States with acoustic windshields. The types of vehicles sporting acoustic windshields stretch across all sizes and price ranges; their use is not limited to luxury vehicles. In fact, the 2008 Ford Focus compact car will have an acoustic windshield as standard equipment. These windshields also are available standard on Ford Escape, Mariner, Expedition, Navigator and Lincoln MKX vehicles.