Active control of sound waves
AssigneeNational Research Development Corporation
InventorMalcolm Alexander Swinbanks
Life of this patent
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Abstract
A sound wave propagated along a duct through a fluid contained in the duct is attenuated by generating sound waves from an array of sound sources spaced along the duct. Each source generates two waves travelling in opposite directions; those travelling in the same direction as the unwanted wave sum to give a resultant which interferes destructively with the unwanted wave, while those travelling in the opposite direction sum to give a negligible resultant. The source array may be operated in response to detection of the unwanted wave.
Claims10
A method of attenuating a sound wave propagating in a given direction along a duct through a fluid contained in the duct, the method comprising:
- generating sound waves from an array of similar sound sources located adjacent the wall of said duct respectively at different positions along said duct, each source generating a pair of sound waves which travel through said fluid in opposite directions along said duct from the position of that source;
- and
- controlling the operation of said array of sources to cause destructive interference to occur between the wave to be attenuated and the resultant of the waves generated by said sources and travelling in said given direction and simultaneously to cause the resultant of the waves generated by said sources and travelling in the direction opposite to said given direction to be negligible.
An apparatus for use in attenuating sound waves propagating along a duct through a fluid contained in the duct, the apparatus comprising:
- an array of similar sound sources located adjacent the wall of said duct respectively at different positions along said duct, each source being capable of generating a pair of sound waves which travel through said fluid in opposite directions along said duct from the position of that source;
- and
- means for operating said array of sources to cause destructive interference to occur between the wave to be attenuated and the resultant of the waves generated by said sources and travelling in said given direction and simultaneously to cause the resultant of the waves generated by said sources and travelling in the direction opposite to said given direction to be negligible.
Dependencies are inferred from the claim text.