Patent ID: 8272475

Claim:
A sound attenuator for low frequencies, comprising: a sound attenuator frame arrangeable in connection with an air-conditioning duct, and comprising a flow duct; and at least one attenuator member operating according to a plate resonator principle, wherein each said at least one attenuator member comprises: a first resonator plate having an outer surface arranged to be the inner wall of the flow duct, such that flow through the flow duct is arranged to travel around said outer surface, said first resonator plate being a steel plate, a framework, said first resonator plate having an inner surface attached to said framework, a second plate substantially parallel to the first resonator plate, said second plate having an inner surface attached to said framework, wherein said second plate, said framework and said first resonator plate outline at least one attenuator unit, said first resonator plate is attached to said framework using laser welding, and said framework includes a pressure balancing opening.