Researchers demonstrated that acoustic levitation can levitate spherical objects much larger than the acoustic wavelength in air. The acoustic levitation of an expanded polystyrene sphere of 50 mm in diameter, corresponding to 3.6 times the wavelength, is achieved by using three 25 kHz ultrasonic transducers arranged in a tripod fashion. In this configuration, a standing wave is created between the transducers and the sphere. The axial acoustic radiation force generated by each transducer on the sphere was modeled numerically as a function of the distance between the sphere and the transducer. The theoretical acoustic radiation force was verified experimentally in a setup consisting of an electronic scale and an ultrasonic transducer mounted on a motorized linear stage. The comparison between the numerical and experimental acoustic radiation forces presents a good agreement.
The levitation capability of the proposed system was confirmed by levitating an expanded polystyrene sphere with a mass of 1.46 g and a diameter of 50 mm.
Although there are several different ways to acoustically levitate an object, most methods use an ultrasonic transducer, which converts electrical signals into ultrasonic waves. The current setup uses three ultrasonic transducers arranged in a tripod fashion around the sphere.
For now the leviation is to a fixed position but they would like to develop new devices capable of levitating and manipulating large objects in air
Acoustic levitation has applications for handling and manipulating various materials, such as very hot materials and liquid samples in space. In microgravity, the lower surface tension allows liquid droplets to reach larger sizes than they do on Earth, and acoustic levitation can be used to control and analyze these large liquid samples.
The International Table Tennis Federation changed the official ball diameter is 40mm and weight of 2.7 grams
The United States Golf Association specifies that a golf ball must weigh no more than 1.620 ounces (45.93g), be spherical in shape and be no less than 1.68-inches (42.7mm) in diameter. This is called “The American Ball”. The “British Ball” is a teensy bit smaller, at 1.62-inches (41.1mm)