General Motors has filed an interesting new patent in Germany, describing a system where the windows of a car effectively become the speakers, doing away with the traditional coil and cone technology that speakers are commonly built around. The document, discovered by CarBuzz at the German Patent and Trade Mark Office, says that coil and membrane-type speakers have several drawbacks, not least of which is that most sound systems have their speakers concentrated in areas like the footwell, where they're far away from the listener's ear.
Another drawback is weight, as the copper-dense speakers we're accustomed to require plenty of materials and take up loads of space. GM's patent aims to address these issues, potentially creating something that provides a more luxurious experience while saving weight - benefits that apply to cars as different as the Escalade and Corvette ZR1.
GM's patent describes laminated glass with embedded piezoelectric exciters (a piezoelectric material is one that can accumulate electrical charge in response to applied mechanical stress). These are at least partially embedded within a polymeric laminating material between glass panes, and in the middle of these laminated panels, a plastic layer with, in one example, polyethylene terephthalate makes the magic happen.
Simply put, when the right current is passed, this plastic layer would turn electrical inputs into mechanical movement, creating vibrations that cause the surrounding glass to propagate and amplify sound waves. The patent also mentions materials such as lead zirconium titanate (used in ultrasound transducers) for the piezoelectric rings, but other compounds and ceramics could also be used here.
GM notes that this would allow speakers to be placed closer to occupants' ears, which means that footwell speakers, headrest speakers, and roof-mounted speakers could be either done away with or minimized, reducing waste and lowering the overall carbon footprint of a car. This system may also draw less power than conventional setups, which is especially important for all-electric vehicles. Another benefit is that these miniature sound implication devices would take up less space in the cabin, which could make cars more efficient and more comfortable.
