Multiple Helmholtz resonators
AssigneeKing Fahd University of Petroleum and Minerals
InventorMuhammad A. Hawwa
Life of this patent
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Abstract
Multiple Helmholtz resonators are combined serially and dynamically to mitigate and/or overcome acoustic noise filtering problems. One Helmholtz resonator is attached to a duct having an acoustic flow path channel containing undesired acoustic signals (noise) and is considered to be an immovable Helmholtz resonator with respect to that flow channel, while at least one movable Helmholtz resonator is movably and acoustically coupled to the immovable Helmholtz resonator. The immovable and movable Helmholtz resonators are acoustically coupled together to adjustably filter two resonant frequencies in the flow path channel with a feedback control system that adjusts the position of the movable Helmholtz resonator in response to the differences in pre-filtered noise versus filtered noise.
Claims10
Multiple Helmholtz resonators for filtering sound in a duct having a neck aperture, comprising:
- an immovable Helmholtz resonator adapted for physically connection to the duct adjacent to the neck aperture and acoustically coupling to the sound in the duct through the neck aperture;
- a movable laminate plate movably coupled to the immovable Helmholtz resonator and forming part of the immovable Helmholtz resonator, the movable laminate plate having a neck aperture;
- a motorized wheel in contract with the movable laminate plate and moving in response to control signals;
- a movable Helmholtz resonator mounted on the movable laminate plate adjacent to the neck aperture in the movable laminate plate and acoustically coupled to the immovable Helmholtz resonator, the plate being movable between a first position in which the movable Helmholtz resonator is out of alignment with the immovable Helmholtz resonator, whereby the immovable Helmholtz resonator functions as a single Helmholtz resonator dampening sound in the duct, and a second position in which the movable Helmholtz resonator is aligned with the immovable Helmholtz resonator, whereby the movable and immovable Helmholtz resonators function as two Helmholtz resonators in series dampening sound in the duct;
- an input microphone adapted for coupling to the duct for producing input signals corresponding to sound in the duct prior to acoustic filtering;
- an error microphone adapted for coupling to the duet for producing error signals corresponding to sound in the duct after acoustic filtering;
- and
- a controller receiving and detecting differences between the input signals and the error signals to produce the control signals, the controller transmitting the control signals to the motorized wheel to control the motorized wheels to position the movable laminate plate and the movable Helmholtz resonator.
A method for using multiple Helmholtz resonators for filtering sound in a duct having a neck aperture, comprising the steps of:
- detecting sound prior to acoustic filtering by the multiple Helmholtz resonators with an input microphone and generating corresponding input signals;
- detecting sound after acoustic filtering by the multiple Helmholtz resonators with an error microphone and generating corresponding error signals;
- comparing the input signals and error signals with a controller, the controller generating control signals;
- transmitting the control signals to a motorized wheel, the motorized wheel adapted to adjustably move a movable laminate plate to position and acoustically couple a movable Helmholtz resonator and an immovable Helmholtz resonator, wherein the movable Helmholtz resonator is mounted on the movable laminate plate adjacent to a neck aperture in the movable laminate plate.
Dependencies are inferred from the claim text.