Patent ID: 7006639
Filing Date: 2006-02-28
Classification: F16L

Abstract:
1. Active noise attenuating duct element, comprising one or more inflow-pipes, the lengths and widths of which are selected to achieve the acoustical behaviour of an air-mass or transmission-line in the frequency range to be attenuated, one or more duct-chambers, arranged such that air flows from said inflow-pipes into said duct-chambers, said duct-chambers being equipped with an outflow-port through which air leaves the chamber, one or more active acoustical impedance elements pneumatically connected to said duct-chambers for influencing the air pressure in these chambers, wherein the lengths and widths of said inflow-pipes and the dimensions of said duct-chambers and the transfer characteristics of said active acoustical impedance elements are adapted to each other to achieve the behaviour of an acoustical low-pass or band-pass filter of higher order, and wherein said active acoustical impedance element further comprises