Piezoelectrics enable displays to provide both audio and touch feedback

The speakers in your smartphone and the system that gives your finger feedback when you touch a virtual button may be relatively small, but they are still big enough to limit how thin our mobile devices can get. Traditional speakers function by running a current through a coil, creating a magnetic field that moves a magnet attached to the speaker cone, which in turn displaces air to create a sound wave. Haptic generators in handsets typically are linear resonant actuators, which are electrically and mechanically like speakers but are optimized to create low-frequency vibrations in a solid rather than sound waves in the air. More recently, some flat-screen TV developers have turned the screens of large-format TVs into speakers using a similar principle. The piezoelectric transducer material requires only one millimeter of enclosure thickness, compared to several millimeters for dynamic speakers or linear resonant actuators, enabling a new generation of thinner handheld devices. Such transducers can produce the sound quality and the loudness of the best miniature dynamic speakers. So if your next phone is thinner, has a longer battery life, and more immersive sound, thank piezoelectrics for eliminating the traditional speakers and motor-based haptic generators from your device, and moving the sound up front, where it belongs.