Abstract: The invention relates to a method and apparatus for the generation of low frequency sound by means of the excitation of a low frequency standing gas borne sound wave. A low frequency sound generator comprises a resonator part and a feeder part with a feeder unit. The method consists of a controlled generation of periodic changes of the gas volume of the resonator part in order to create a standing sound wave. The invention also includes a feeder unit for the working of the method. The feeder unit comprised of three rotating parts, namely one center rotor and two side rotors, the rotation of which are synchronized. The feeder unit is open on two sides, each side communicating with one tubular resonator. The rotors are provided with cut out portions and the center rotor is also provided with a protruding vane-shaped part.

Abstract: A method and arrangement for enforced heat transmission between a solid or liquid alimentary body and an ambient gas takes place in connection with cooling/freezing or when cooking, frying or drying the entire part or parts of the alimentary body. This method and arrangement uses a low-frequency standing sound wave. The apparatus uses a low-frequency sound generator having a pulsator part and a resonator part. The resonator part is acoustically virtually closed and is designed so that the alimentary body, which is to be exposed to enforced heat transmission, is located within a zone inside the resonator part where the standing sound wave has a particle velocity anti-node.

Abstract: The invention relates to a frequency controlled motor driven low frequency sound generator. The low frequency sound generator consists of an open resonator (2) arranged as a sound emitter for generating standing gas-borne sound waves which produce a varying gas pressure inside the resonator, and a feeder unit (1) for a modulated supply of air pulses to the resonator. The feeder unit (1) comprises a motor driven piston (8) with an approximately sinusoidal volume velocity. The piston is mounted on a piston rod (7) which is connected to a flywheel (6). The flywheel, in its turn, is mounted on a shaft (5) which is driven by a motor (3). The motor speed and thereby the frequency of the piston is regulated by a special electronic control unit.

Abstract: The invention relates to method and apparatus for the combustion of fluidal fuels. The fuel is dispersed in combustion air and, in order to improve the combustion rate and efficiency, is exposed to a high particle velocity of a sound produced by a low frequency sound generator. The frequency of the sound is determined by the sound generator, the maximum frequency being 30 Hz. A reciprocating movement of combustion air and fuel particles entrained therein is obtained. The sound generator is a quarter wave type sound generator with a tubular resonator forming a diffuser at the open end thereof.

Abstract: Method and apparatus for infrasonically intensifying a glow bed (13), supported by a grate (12). In order to improve the beneficial effect of sound on combustion the bed of fuel, located on the grate, is exposed to a high particle velocity of a sound positively produced by an external low frequency sound generator (11) the frequency of which is determined by the sound generator, to provide a reciprocating movement of combustion air and combustion gas through the glow bed. The dimensions of the grate in a plane transverse to the reciprocating movement of combustion air and combustion gas are less than a quarter of the wave-length of the sound generated by the sound generator.

Abstract: The invention relates to method and apparatus for the combustion of large solid fuels. In order to improve the beneficial effect of sound on combustion are a bed of the fuel located on a grate, the bed of fuel is exposed to a high particle velocity of a sound positively produced by an external low frequency sound generator, the frequency of which is determined by the sound generator, to provide a reciprocating movement of combustion air and combustion gas through the fuel bed. The dimensions of the grate in a plane transverse to the reciprocating movement of combustion air and combustion gas are less than a quarter of the wave length of the sound generated by the sound generator.

Abstract: A low-frequency sound generator for generating intense sound, which generator includes an open resonator tube. Pressurized gas is supplied to the resonator tube as pulses through a feeder system which includes a valve slide member which controls the pressure of the supplied gas. The gas pulses develop standing sound waves in the resonator tube which provides a varying gas pressure. Means in the resonator tube is operable in response to changes in the gas pressure to provide positive feedback of the sound pressure in the resonator tube to the feeder system at a resonant frequency of the resonator tube.

Abstract: A low-frequency sound generator for generating intense sound, which generator includes an open resonator tube. Pressurized gas is supplied to the resonator tube as pulses through a feeder system which includes a valve slide member which controls the pressure of the supplied gas. The gas pulses develop standing sound waves in the resonator tube which provides a varying gas pressure. Means in the resonator tube is operable in response to changes in the gas pressure to provide positive feedback of the sound pressure in the resonator tube to the feeder system at a resonant frequency of the generator.