Significance Humans and other animals effectively use acoustic waves to communicate with each other. Ultrasonic acoustic waves are intriguing because they do not interfere with normal voice communication and can be highly directional with long range. Therefore, wireless ultrasonic radio is a useful communications method. Here we find that graphene has mechanical properties that make it ideally suited for wide-band ultrasonic transduction. Using simple and low-cost fabrication methods we have produced an ultrasonic microphone and ultrasonic radio prototypes. When acting as loudspeaker/microphone alone, the graphene-based acoustic devices also show ideal flat-band frequency response spanning the whole audible region as well as ultrasonic region to at least 0.5 MHz; such flat frequency response has significant acoustic applications implications.