Abstract: Various embodiments concern piezoelectric sensors that can be used as ultrasonic transmitters and/or receivers. Piezoelectric sensors can be embedded within, or connected to, a medium. For example, a piezoelectric sensor could be embedded within a chassis, a protective substrate disposed above a display, or a substrate laid within a break in the chassis. An array of piezoelectric sensors can generate a high-frequency ultrasound vibration field that is continuously and uniformly propagated across the medium. These propagating ultrasound waves enable detection of objects touching the surface of the medium. More specifically, during a touch event, ultrasound waves will be reflected back toward the piezoelectric sensors. A controller can determine the location of the touch event based on which piezoelectric sensor(s) detect reflected ultrasound waves and/or characteristic(s) of those reflected ultrasound waves.