Active acoustic attenuation system for reducing tonal noise in rotating equipment
US5010576A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 22, 1990 |
| Grant date | Apr 23, 1991 |
| Priority date | — |
| Expiry date | Jan 22, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG10K2210/511
- WIPO fieldOther consumer goods
- WIPO sectorOther fields
Abstract
An active acoustic attenuation system for attenuating tonal blade pass noise in a multi-bladed fan uses a sinusoidal rotational speed signal produced by an accelerometer mounted on the fan as the reference signal for a filtered-X LMS (least mean squarae) adaptive filter controlling a canceling sound generating speaker. The sinusoidal signal is clipped by a zero crossing detector to produce a rectangular wave signal having harmonics which include the fundamental and harmonics of the tonal noise to be eliminated. When the system is used with axial flow fans having a central hub, the speaker is mounted facing the fan and coaxial with the hub. When the fan has a straight discharge conduit, the speaker is no larger in diameter than the fan hub to preclude restricting flow; however, there is no restriction on the size of a speaker facing the fan when it is mounted in the rear wall of a discharge chamber having a lateral discharge opening.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.