Rich and full, but not very deep

Automotive Design & Production, Jan, 2003 by Christopher A. Sawyer

For years inferior engineers have been working diligently to stop panel resonance within a vehicle. Now they're being asked by NXT Technology, Inc. (London, England) to embrace this phenomenon for the purpose of creating audio system speakers. The company's SurfaceSound technology employs small "exciters" to utilize the natural resonance frequencies of stiff, light panels in order to produce sound. Because the entire array is only a few millimeters thick, NXT speakers take up much less room than their bulkier cane-style counterparts.

"The panels act like the sound board of a piano," says Andrew Williams, NXT's director of Marketing, "so sound disperses evenly across the panel, which eliminates the 'hot' and 'cold' sound spots cone speakers create in a vehicle interior." This has caused a number of OEMs to investigate using NXT technology for an instrument panel-mounted center channel unit in existing applications, and with left and right-hand speakers in new designs. "The packaging advantages drive them to the technology," says Williams, "but there is an in-creasing interest in our ability to disperse the sound so evenly." And since European authorities have banned the use of non-hands-free phones in cars, a number of companies have expressed interest in a center channel that can be hidden atop the instrument panel.

Philips Sound Solutions has recently signed on to develop a new generation of off-the-shelf exciters for automotive applications. They join Visteon, Intier, Alpine, Harman International, Fujitsu Ten, Takehiro, and Owens Corning as licensees of the technology. Owens Corning is developing an optimized trim material that will allow the exciter to be mounted directly to a trim panel, with no need for a separate grille or acoustic radiator surface. Cars with this technology aren't expected before the 2008-2010 time period, while those using a grille or other thin panel separate from the trim unit will hit the market in the 2005 model year.

"We have two projects nearing a decision in North America, and two more in Europe," Williams says. The claimed weight reductions of 20% to 45% and cost reductions of up to 30% have caused one of the European OEMs to target this technology for a commodity vehicle, not a high-line car.