Touch events can be detected using an ultrasound input device coupled to a surface, such as a surface of a piece of furniture or electronic device. The ultrasound input device can generate ultrasonic waves in the surface, the reflections of which can be measured by the ultrasound input device. When a touch is made to the surface (e.g., opposite the ultrasound input device), the physical contact can absorb some of the energy of the outgoing ultrasonic waves (e.g., the originally transmitted wave and any subsequent outgoing reflections). Energy measurements associated with the measured reflections can thus be used to identify touch events. Various techniques can be used to make the energy measurements and reduce identification of false touch events.