Noise cancelling device
View Patent ↗A noise cancelling device includes first and second expansion chambers, both cylindrical and equipped with double-wall inlet and outlet extension pipes. Each expansion chamber includes two elements: the first elements includes first and second cylindrical portions with differing diameters, and the second element includes a third cylindrical portion connecting to a connecting pipe. The second element is slidingly engaged with the first element to form a cylindrical body. The expansion chambers, the connecting pipe, and the extension pipes form a unitary body, and axially aligned along a longitudinal axis in the order of inlet extension pipe, first expansion chamber, connecting pipe, second expansion chamber, and outlet extension pipe. The device has a plane of symmetry perpendicular to the longitudinal axis at a center point of the connecting pipe.
1 . A noise cancelling device, comprising:
a first expansion chamber and a second expansion chamber, each having a cylindrical shape with a first end and a second end;
an inlet extension pipe having a double wall, connected to the first end of the first expansion chamber;
an outlet extension pipe having a double wall, connected to the first end of the second expansion chamber; and
a connecting pipe, connecting the second end of the first expansion chamber and the second end of the second expansion chamber;
wherein each expansion chamber comprises:
a first element comprising:
a first cylindrical portion having a double wall and a first diameter;
a first circular base connecting to the first cylindrical portion;
a second cylindrical portion connecting to the first circular base having a double wall and a second diameter,
wherein the first and second cylindrical portions are axially aligned;
wherein the first diameter is larger than the second diameter;
wherein the first cylindrical portion has an extending outer lip;
wherein the second cylindrical portion is slidingly engaged with the extension pipe; and
wherein an inner wall of the second cylindrical portion is disposed in a gap of the double wall of the extension pipe;
a second element comprising:
a third cylindrical portion having a third diameter; and
a second circular base connecting to the third cylindrical portion and the connecting pipe,
wherein the second element is slidingly engaged in a gap of the double wall of the first element to form a cylindrical body; and
wherein each of the expansion chambers, the connecting pipe, and the extension pipes have an inner diameter and an outer diameter;
wherein the expansion chambers, the connecting pipe, and the extension pipes form a unitary body, wherein the expansion chambers, the connecting pipe, and the extension pipes are axially aligned along a longitudinal axis of all the cylindrical portions in the order of inlet extension pipe, first expansion chamber, connecting pipe, second expansion chamber, and outlet extension pipe, having a plane of symmetry perpendicular to the longitudinal axis at a center point of the connecting pipe.
2 . The noise cancelling device of claim 1 , wherein the connecting pipe and the second cylindrical portion of each expansion chamber have the same inner diameter.
3 . The noise cancelling device of claim 1 , wherein the first element of each expansion chamber is movable, and an elastomeric lining is present between an inner contacting surface of the first element and the second element to form an interior surface having a single diameter when the elastomeric lining is in a resting state.
4 . The noise cancelling device of claim 1 , wherein the expansion chambers are configured to be extended or retracted by adjusting a length of the expansion chamber.
5 . The noise cancelling device of claim 1 , wherein the connecting pipe is a fix-length pipe.
6 . The noise cancelling device of claim 1 , wherein the connecting pipe and each of the expansion chambers have the same length at a default position.
7 . The noise cancelling device of claim 1 , wherein the connecting pipe has an inner diameter smaller than the inner diameter of the expansion chamber.
8 . The noise cancelling device of claim 1 , wherein each extension pipe further comprises a plurality of springs configured to return the first element of each expansion chamber at the default position.
9 . The noise cancelling device of claim 1 , wherein each extension pipe has an inner diameter smaller than the inner diameter of the expansion chamber.
10 . The noise cancelling device of claim 1 , wherein the inner diameter of each extension pipe is the same as the inner diameter of the connecting pipe.
11 . The noise cancelling device of claim 1 , further comprising:
a control system to actuate a size of the expansion chamber by adjusting a length of the expansion chamber, comprising:
a controller;
an actuator mounted on an outer wall of the extension pipe and connected to the first base of the expansion chamber through a cable; and
a sensor for the expansion chamber on the actuator;
wherein the controller includes a circuitry configured to receive and process data from the sensor and giving commands to the actuator;
wherein the actuator is configured to execute commands from the controller to adjust the length of each expansion chamber; and
wherein the actuator is configured to detect the length of the expansion chamber.
12 . The noise cancelling device of claim 1 , wherein the controller receives the data from the sensor either through a cable or a wireless transmission.
13 . The noise cancelling device of claim 1 , wherein the controller gives commands to the actuator through a cable or a wireless transmission.
14 . The noise cancelling device of claim 1 , wherein the controller gives commands based on a chirp function's feedback.
15 . The noise cancelling device of claim 1 , wherein a transmission loss in the noise cancelling device follows a mathematical description as:
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wherein i is the standard imaginary unit;
wherein m represents an area ratio between the first expansion chamber and the connecting pipe;
wherein n represents an area ratio between the second expansion chamber and the connecting pipe;
wherein L1 represents the length of the first expansion chamber;
wherein L2 represents the length of the connecting pipe; and
wherein L3 represents the length of the second expansion chamber.
16 . The noise cancelling device of claim 1 , wherein the device has a stopband location either to a left or right of the center frequency within a frequency spectrum of 0 to 5000 Hz.
17 . The noise cancelling device of claim 1 , wherein the expansion chambers are capable of adjusting their lengths in real-time.
18 . A method of noise reduction on a system providing a flow of gas using the noise cancelling device of claim 1 , comprising:
connecting the noise cancelling device to a gas exhaust/flow to generate acoustic signals;
processing the acoustic signals to generate a feedback; and
adjusting the lengths of expansion chamber based on the feedback to reduce the noise.
19 . The method of claim 18 , reduces noise within a frequency spectrum of 0 to 5000 Hz.
20 . The method of claim 18 , wherein the system provides a flow of gas selected from the group consisting of exhaust system, car muffler system, air handling system, ducted pumps, air discharge line, and compressors.