Methods and systems for active sound attenuation in a fan unit
A system and method for controlling noise produced by an air handling system, for example, is provided. The system includes a source microphone to collect sound measurements from the air handling system and a processor to define a cancellation signal that at least partially cancels out the sound measurements. The system also includes a speaker to generate the cancellation signal. The sound measurements are at least partially canceled out within a region of cancellation. Accordingly, the system further includes a response microphone to collect response sound measurements at the region of cancellation. The processor tunes the cancellation signal based on the response sound measurements.
1. A fan unit, comprising:
a fan operatively connected to a motor; and
an inlet cone proximate to the fan, wherein the inlet cone comprises:
a throat proximate the fan;
a distal inlet; and
a noise control extension extending between the throat and the distal inlet, wherein the noise control extension has a sound-absorbing layer configured to passively attenuate sound generated by the fan unit.
2. The fan unit of claim 1 , further comprising:
a source microphone configured to collect sound produced by the fan unit; and
a speaker configured to generate a cancellation sound field that at least partially cancels the sound.
3. The fan unit of claim 1 , wherein the noise control extension further comprises a perforated tube, wherein the sound-absorbing layer wraps around at least a portion of the perforated tube.
4. The fan unit of claim 1 , wherein the noise control extension further comprises a support tube that wraps around at least a portion of the sound-absorbing layer.
5. The fan unit of claim 2 , wherein the source microphone and the speaker are directly or indirectly secured to the support tube.
6. The fan unit of claim 1 , wherein the sound-absorbing layer is formed of an open-cell sound-absorbing material.
7. The fan unit of claim 1 , wherein the noise control extension is cylindrical.
8. The fan unit of claim 1 , wherein the noise control extension comprises a diameter that differs throughout at least a portion of a length of the noise control extension.
9. The fan unit of claim 2 , further comprising at least one response microphone configured to provide a feedback loop to the speaker.
10. The fan unit of claim 2 , further comprising a module configured to define the cancellation signal that at least partially cancels out the sound measurements.
11. A fan unit, comprising:
a fan operatively connected to a motor;
an inlet cone proximate to the fan, wherein the inlet cone includes a noise control extension having a sound-absorbing layer configured to passively attenuate sound generated by the fan unit;
a source microphone configured to collect sound produced by the fan unit;
a speaker configured to generate a cancellation sound field that at least partially cancels the sound; and
at least one response microphone configured to provide a feedback loop to the speaker.
12. A method of attenuating noise within a fan unit, wherein the fan unit comprises a fan operatively connected to a motor and an inlet cone proximate to the fan, the method comprising:
disposing a noise control extension having a sound-absorbing layer that is configured to passively attenuate sound generated by the fan between a throat and distal end of the inlet cone; and
passively attenuating noise generated within the fan unit with the noise control extension.
13. The method of claim 12 , further comprising actively attenuating noise generated within the fan unit, wherein the actively attenuating noise operation comprises collecting sound generated by the fan unit through a source microphone, and generating a cancellation sound field that at least partially cancels the sound through a speaker.
14. The method of claim 12 , wherein the passively attenuating noise operation further comprises:
supporting the sound-absorbing layer with a perforated tube; and
allowing sound to pass into the sound-absorbing layer through the perforated tube.
15. The method of claim 12 , wherein the passively attenuating noise operation further comprises supporting the sound-absorbing layer with a support tube that wraps around at least a portion of the sound-absorbing layer.
16. The method of claim 13 , further comprising securing the source microphone and the speaker to the support tube.
17. The method of claim 12 , further comprising forming the sound-absorbing layer from an open-cell sound-absorbing material.
18. The method of claim 13 , further comprising using at least one response microphone to provide a feedback loop to the speaker.
19. The method of claim 13 , wherein the actively attenuating operation further comprises defining the cancellation signal with a module.
20. A method of attenuating noise within a fan unit, wherein the fan unit comprises a fan operatively connected to a motor and an inlet cone proximate to the fan, the method comprising:
passively attenuating noise generated within the fan unit with a noise control extension having a sound-absorbing layer configured to passively attenuate sound generated by the fan;
actively attenuating noise generated within the fan unit, wherein the actively attenuating noise operation comprises collecting sound generated by the fan unit through a source microphone, and generating a cancellation sound field that at least partially cancels the sound through a speaker; and
using at least one response microphone to provide a feedback loop to the speaker.
21. A fan unit, comprising:
a noise control extension configured to extend between a throat and a distal inlet of an inlet cone, wherein the noise control extension has a sound-absorbing layer configured to passively attenuate sound generated by a fan unit;
a source microphone configured to collect sound produced by the fan unit; and
a speaker configured to generate a cancellation sound field that at least partially cancels the sound.
22. The fan unit of claim 21 , wherein the noise control extension further comprises a perforated tube, wherein the sound-absorbing layer wraps around at least a portion of the perforated tube.
23. The fan unit of claim 21 , wherein the noise control extension further comprises a support tube that wraps around at least a portion of the sound-absorbing layer.
24. The fan unit of claim 23 , wherein the source microphone and the speaker are directly or indirectly secured to the support tube.
25. The fan unit of claim 21 , wherein the sound-absorbing layer is formed of an open-cell sound-absorbing material.
26. The fan unit of claim 21 , wherein the noise control extension is cylindrical.
27. The fan unit of claim 21 , wherein the noise control extension comprises a diameter that differs throughout at least a portion of a length of the noise control extension.
28. The fan unit of claim 21 , further comprising at least one response microphone configured to provide a feedback loop to the speaker.
29. The fan unit of claim 21 , further comprising a module configured to define the cancellation signal that at least partially cancels out the sound measurements.
30. A fan unit, comprising:
a noise control extension having a sound-absorbing layer configured to passively attenuate sound generated by a fan unit;
a source microphone configured to collect sound produced by the fan unit;
a speaker configured to generate a cancellation sound field that at least partially cancels the sound; and
at least one response microphone configured to provide a feedback loop to the speaker.