Abstract: An acoustic levitation system is provided for acoustically levitating an object, by applying a single frequency from a transducer into a resonant chamber surrounding the object. The chamber includes a stabilizer location (29, FIG. 2) along its height, where the side walls of the chammber are angled so they converge in an upward direction. When an acoustic standing wave pattern is applied between the top and bottom of the chamber, a levitation surface (28) within the stabilizer does not lie on a horizontal plane, but instead is curved with a lowermost portion (31) near the vertical axis of the chamber. As a result, an acoustically levitated object (30) is urged by gravity towards the lowermost location (31) on the levitation surface, so the object is kept away from the side walls of the chamber.

Abstract: Methods are described for using acoustic energy to agglomerate fine particles on the order of one micron diameter that are suspended in gas, to provide agglomerates large enough for efficient removal by other techniques. The gas with suspended particles, is passed through the length of a chamber (24) while acoustic energy at a resonant chamber mode is applied to set up one or more acoustic standing wave patterns (40,42,44) that vibrate the suspended particles to bring them together so they agglomerate. Several widely different frequencies can be applied to efficiently vibrate particles of widely differing sizes. The standing wave pattern can be applied along directions (R in FIG. 3) transversed to the flow of the gas. The particles can be made to move in circles by applying acoustic energy in perpendicular directions (P,Q in FIG. 6) with the energy in both directions being of the same wavelength but 90.degree. out of phase.

Abstract: A system is described for acoustically levitating an object (12, FIG. 1) within a portion of a chamber (14) that is heated to a high temperature, while a driver (22) at the opposite end of the chamber is maintained at a relatively low temperature. The cold end of the chamber is constructed so it can be telescoped to vary the length (L.sub.1) of the cold end portion and therefore of the entire chamber, so that the chamber remains resonant to a normal mode frequency, and so that the pressure at the hot end of the chamber is maximized. The precise length of the chamber at any given time, is maintained at an optimum resonant length by a feedback loop. The feedback loop includes an acoustic pressure sensor (42) at the hot end of the chamber, which delivers its output to a control circuit (44), which controls a motor (36) that varies the length (L) of the chamber to a level where the sensed acoustic pressure is a maximum.

Abstract: A system is described for use with acoustically levitated objects, which enables close control of rotation of the object. One system includes transducers (18, 20, 22) that propagate acoustic waves along the three dimensions (X, Y, Z) of a chamber (16) of rectangular cross section. Each transducer generates a first wave which is resonant to a corresponding chamber dimension to acoustically levitate an object, and additional higher frequency resonant wavelengths for controlling rotation of the object. The three chamber dimensions and the corresponding three levitation modes (resonant wavelengths) are all different, to avoid degeneracy, or interference, of waves with one another, that could have an effect on object rotation. Only the higher frequencies, with pairs of them (e.g. 50, 52) having the same wavelength, are utilized to control rotation, so that rotation is controlled independently of levitation and about any arbitrarily chosen axis.

Abstract: A system is described for acoustically moving an object within a chamber, by applying wavelengths of different modes to the chamber to move the object between pressure wells formed by the modes. In one system, the object (96, FIG. 7) is placed in a first end portion of the chamber while a resonant mode is applied along the length of the chamber that produces a pressure well (86) at that location. The frequency is then switched to a second mode that produces a pressure well (100) at the center of the chamber, to draw the object thereto. When the object reaches the second pressure well and is still travelling towards the second end of the chamber, the acoustic frequency is again shifted to a third mode (which may equal the first mode) that has a pressure well (106) in the second end portion of the chamber, to draw the object thereto.