Abstract: A loudspeaker has a rigid sound radiator having a free edge and a electromagnetic drive mounted on an opposed hub edge and arranged to produce a torque on the radiator. Either a coil or a permanent magnet of the drive is mounted directly on the hub edge and has a radius which is substantially smaller than the radius of the radiator.

Abstract: The present invention is drawn to a method of stabilizing the motion of a levitated object. The method involves continuously determining the motion of a levitated object, relative to a given point, and deriving the velocity of the object from the determined motion. A continuous, non-contact, corrective force is applied to the object in the opposite direction and proportional to the derived velocity.

Abstract: A device for providing electromagnetic levitating forces and heating is described. A plurality of separate coils are provided, each powered by a separate power amplifier. Each coil may be supplied with two separate frequencies, one to levitate, and the other to heat the object. Also, the coils may be driven at separate phases to more uniformly distribute the magnetic levitating and heating forces.

Abstract: Low frequency, high intensity sound is produced using a conduit having a flow of high velocity and low pressure air. A pair of sound ports are provided in the conduit, and a rotary valve connected to a reversible servomotor and audio source is employed to direct the flow of air toward and away from the ports.

Abstract: An acoustic levitator device for suspending a specimen object under the influence of gravity without contact with a solid surface comprising in combination gas levitation means for directing a concentrated flow of gas along an axis upwardly against the object to provide a force to lift a majority weight of the object, and acoustic levitation means for exerting an acoustic positioning force on said object to restrain movement away from said axis and to hold said object in a given position.

Abstract: An acoustic levitator includes a pair of opposed sound sources which have interfering sound waves producing acoustic energy wells in which an object may be levitated. The phase of one sound source may be changed relative to the other in order to move the object along an axis between the sound sources.

Abstract: A sound source includes a plurality of drivers communicating with the common throat of a horn. The size of the radiating area of the throat is less than two or three wavelengths of the highest frequency to be produced such that the drivers operate conjointly from a virtual point. Means may be included to adjust the time delay or phase between drivers to control the dispersion angle.

Abstract: A sound source coupled to an acoustic levitation chamber is provided with horn loading to improve efficiency and to protect the sound source from heat. A dish sound source may be used, and the horn may include a half wavelength pathway from the rear of the dish to provide additional efficiency.

Abstract: At least one rotary vane in a tube is driven by a motor in response to an audio signal, causing production of sound through at least one opening in the tube.

Abstract: A sound transducer having a high impedance relative to air is coupled with mechanical transformers. The output transformer is in the shape of a dish having the center coupled to a piezoelectric transducer, the outer portion of the dish is unsupported and more flexible than the center section at resonance this allows large amplitude movement and a better impedance match to air.

Abstract: An electrical blower is used to pass cooling air through a loudspeaker driver. The blower is connected in parallel to the leads between the amplifier and speaker such that the blower speed and cooling increases with increased power consumption and heat generation by the driver.

Abstract: A method and apparatus for producing low frequency sound (20 to 100 Hz) at levels of intensity above the minimum threshold of human hearing. A mechanical-electrical drive having high power capacity is coupled via a linkage to a sound radiator and is responsive to the electrical input from a sound program source. The drive is capable of large excursions at high forces which are substantially constant irrespective of the extent of excursion.

Abstract: An improvement is provided in a loudspeaker having a current carrying coil disposed in the flux gap of a permanent magnet and carrying current to drive the coil and an associated sound diaphragm. The coil is substantially longer than the thickness of the flux gap and has an exposed conductive surface. Contacts are mounted near each side of the flux gap and slidably engage the coil surface to supply current to a limited portion of the coil situated in the flux gap, irrespective of movement of the coil.

Abstract: Objects are levitated in a sound system substantially free of reverberation and reflection by positioning a small reflector in the path of sound waves. Interference between the primary waves and reflected waves creates a localized zone of minimized energy closely adjacent to the reflector in which an object may be stably levitated. The energy well thus produced is not dependent upon distance from the sound source, and the levitated object may be moved in any direction by moving the reflector. A plurality of reflectors may be employed to manipulate and combine levitated materials, and improvements in the processing of levitated objects are also achieved.