Method and equipment for attenuating sound in a duct

Details Method and equipment for attenuating sound in a duct Method and equipment for attenuating sound in a duct

2005-01-25

2005-01-25

Mei, Xu (Department: 2644)

Electrical audio signal processing systems and devices

Acoustical noise or sound cancellation

Within duct

C381S071700

Reexamination Certificate

active

06847722

ABSTRACT:
The invention relates to a method and an equipment for attenuating sound in a duct. Sound propagating in a duct is detected by means of a detector (2) and attenuated by using two successive monopole elements (3, 4) in such a way that both elements function as a dipole approximation and the elements are also used to approximatively produce the monopole radiation needed. A dipole control signal is fed to both elements (3, 4) at a phase shift which is 180° between the two elements. In addition, a monopole control signal is fed to the same elements (3, 4), only this time cophasally. Total volume velocities produced by the two elements (3, 4) are combinations of the portions obtained from the monopole and dipole sources.

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