Photo: DaimlerChrysler

The Dodge MAXXcab concept truck is the first automotive application of Audio Spotlight™ - an MIT Media Lab technology that directs a narrow beam of sound much like a spotlight projects light. Only the person whom the sound beam is "shined" at can hear it. This makes it possible for each passenger to listen to something completely different without interfering with each other. 

"The variety of sound sources is only going to increase with the availability of voice-enabled navigation, e-mail, cell phones, video games and movies in your future vehicle," said Steve Buckley, electrical product innovation manager at DaimlerChrysler Corp. "The Dodge MAXXcab is great test bed for this technology because it already includes features such as the back-seat 'Edu-tainment' system for the kids and front-seat plug-and-play computer with voice-activated features."  

In the MAXXcab, four Audio Spotlights are imbedded in the headliner directly above the passengers. Two speakers "shine" on the front-seat passengers while the other speakers are aimed at rear-seat passengers creating two distinct audio environments. In future applications, each passenger could have a unique sound environment, Buckley said.  

The technology was developed as an MIT Media Lab project by 27-year-old Joe Pompei. The MIT student and occasional musician was frustrated by the inability to control sound from traditional speakers. "The location of sound, and how it is distributed around the listener, greatly defines the listening experience," Pompei explains. "We're used to doing this with light -- we already use light bulbs, spotlights and projectors to control our visual environment. With the Audio Spotlight, we can now have the same control over sound."  

The Audio Spotlight consists of a thin, circular transducer array and a specially designed signal processor and amplifier. The lightweight transducer is about one-half inch thick and nonmagnetic. The signal processor and amplifier are integrated into a system about the same size as a traditional audio amplifier and it has similar power requirements. 

Unlike traditional speakers that transmit non-directed audible sound at wavelengths of several feet, the Audio Spotlight transmits millimeter-sized, ultrasonic waves which form a very narrow beam of sound which becomes audible as it travels through the air. The current system produces relatively low-volume sound at typical passenger positions as it has not been optimized for close-range listening, Pompei said. It is currently designed for long-range projection and further development in transducer design will solve that problem, he added.   

The Audio Spotlight technology is still in development research and has commercial interest from several MIT Media Lab sponsors representing a variety of industries, Pompei said. None of the technologies in the system are inherently expensive, and many components are actually smaller than today's systems, according to Pompei. If produced in volume, he anticipates it could be competitively priced with conventional audio systems. 

(June 12, 2000)