Not so, if you use a pair of specialised ultrasonic transducer arrays to move the air instead! (Video, embedded below) Three banks of thrusters provide a 180 degree steerable net force Details are ...

Ultrasonic Transducer Applications Ultrasound transducers ... as well as flexible composites that can be adapted to complex ...

Types of Ultrasound Used in Prenatal Screening There ... This is the most common type, where the transducer is moved across ...