HK1160280A - Methods and systems for active sound attenuation in an air handling unit - Google Patents

Description

Method and system for active sound attenuation in air handling units

Cross Reference to Related Applications

The present application relates to and claims priority from provisional application serial No. 61/324,634 entitled "METHODS and systems FOR ACTIVE SOUND attached identification IN AN AIR HANDLING UNIT", filed on 15.4.2010, the entire subject matter of which is hereby expressly incorporated by reference in its entirety.

Technical Field

Embodiments relate to air handling units, and more particularly, to methods and systems for efficient acoustic attenuation in air handling units.

Background

Air handling systems (also referred to as air handlers) are conventionally used to condition air in buildings or rooms (hereinafter "structures"). The air handling system may include various components, such as cooling coils, heating coils, filters, humidifiers, fans, sound attenuators, controls, and other equipment that operate to at least meet a specified air capacity, which may represent all or only a portion of the total air handling requirements of the structure. The air handling system may be manufactured in a factory and brought to a structure to be installed, or it may be built on site using appropriate equipment to meet a specified air capacity. An air handling compartment of an air handling system includes a fan inlet cone and an exhaust plenum. A fan unit, including an inlet cone, a fan, a motor, a fan frame, and any accessories related to the function of the fan (e.g., dampers, controls, settling devices, and associated boxes), is located within the air handling compartment. The fan includes a fan wheel having at least one blade. The fan wheel has a fan wheel diameter measured from one side of the outer circumference of the fan wheel to an opposite side of the outer circumference of the fan wheel. The dimensions of the air handling compartment, such as height, width and duct length, are determined by reference to fan manufacturer data for the selected fan type.

During operation, each fan unit generates sound at some frequency. In particular, smaller fan units generally emit acoustic power at higher audible frequencies, while larger fan units emit greater acoustic power at lower audible frequencies. Devices have been proposed in the past to provide passive acoustic attenuation, for example using sound absorbing tiles or barriers that block or reduce the propagation of noise. The sound absorption tiles include soft surfaces that attenuate reflected sound waves and reverberations of the fan unit.

However, passive sound attenuation devices typically affect noise propagation in certain directions relative to the direction of airflow.

There remains a need for improved systems and methods for providing acoustic attenuation in air handling systems.

Disclosure of Invention

In one embodiment, a method for controlling noise generated by an air handling system is provided. The method includes collecting sound measurements from the air handling system, wherein the sound measurements are defined by acoustic parameters. The value of the acoustic parameter is determined based on the collected sound measurements. Offset values of the acoustic parameters are calculated to define a cancellation signal that at least partially cancels the acoustic measurement when the cancellation signal is generated. The acoustic parameters may include frequency and amplitude of the acoustic measurements. Optionally, the cancellation signal comprises opposite phases and matching amplitudes of the acoustic parameters. Optionally, the response sound measurements are collected in a cancellation zone, and the cancellation signal is tuned based on the response sound measurements.

In another embodiment, a system for controlling noise generated by an air handling system is provided. The system includes a source microphone that collects sound measurements from the air handling system, and a processor that defines a cancellation signal that at least partially cancels the sound measurements. The system also includes a speaker that generates a cancellation signal. Optionally, the loudspeaker produces a cancellation signal in the opposite direction to the sound measurement. Optionally, the sound measurements are at least partially cancelled in a cancellation zone, and the system further comprises a response microphone collecting response sound measurements in the cancellation zone. Optionally, the processor tunes the cancellation signal based on the response sound measurement.

In another embodiment, a fan unit for an air handling system is provided. The fan unit includes a source microphone that collects sound measurements from the fan unit. The module defines a cancellation signal that at least partially cancels the sound measurement. The loudspeaker produces a cancellation signal.

Drawings

FIG. 1 is a perspective view of an air handler in accordance with one embodiment.

FIG. 2 is a perspective view of a set of fan arrays according to one embodiment.

FIG. 3 is a schematic diagram of a fan unit according to one embodiment.

FIG. 4 is a flow diagram of a method for a dynamic feedback loop, according to one embodiment.

Fig. 5 is a flow diagram of a method for providing active acoustic attenuation according to one embodiment.

Fig. 6 is a graphical plot of the active acoustic attenuation method corresponding to fig. 5.

FIG. 7 is a schematic diagram of a fan unit according to one embodiment.

FIG. 8 is a cross-sectional view of an inlet cone according to one embodiment.

FIG. 9 is a schematic diagram of a fan unit according to one embodiment.

FIG. 10 is a schematic diagram of an active-passive sound attenuator, according to one embodiment.

FIG. 11 is a graph illustrating attenuated noise frequencies according to one embodiment.

FIG. 12 is a side view of an inlet cone formed in accordance with an embodiment.

FIG. 13 is a side view of a fan unit formed in accordance with an embodiment.

FIG. 14 is a front perspective view of a fan unit formed in accordance with an embodiment.

Fig. 15 is a front perspective view of a fan unit formed in accordance with an embodiment and having a microphone located therein.

Detailed Description

The foregoing summary, as well as the following detailed description of certain embodiments, will be better understood when read in conjunction with the appended drawings. To the extent that the figures illustrate diagrams of the functional blocks of various embodiments, the functional blocks are not necessarily indicative of the division between hardware circuitry. Thus, for example, one or more of the functional blocks (e.g., processors or memories) may be implemented in a single piece of hardware (e.g., a general purpose signal processor or random access memory, hard disk, or the like) or multiple pieces of hardware. Similarly, the programs may be stand alone programs, may be incorporated as subroutines in an operating system, may be functions in an installed software package, and the like. It should be understood that the various embodiments are not limited to the arrangements and instrumentality shown in the drawings.

As used herein, an element or step recited in the singular and proceeded with the word "a" or "an" should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly recited. Furthermore, references to "one embodiment" are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments "comprising" or "containing" an element or a plurality of elements having a particular property may include additional such elements not having that property.

FIG. 1 illustrates an air handling system 200 utilizing a fan array air handling system according to an embodiment of the present invention. The system 200 includes an inlet 202 that receives air. A heating section 206 to heat the air is included and followed by an air treatment section 208. A humidifier section 210 is located downstream of the air treatment section 208. The humidifier part 210 adds moisture and/or removes moisture from the air. Cooling coil sections 212 and 214 are located downstream of humidifier section 210 to cool the air. A filter section 216 is located downstream of the cooling coil section 214 to filter the air. These portions may be rearranged or removed. An add-on portion may be included.

The air handling section 208 includes an inlet chamber 218 and an outlet chamber 220 separated from each other by a partition wall 225, the partition wall 225 forming part of a frame 224. The fan inlet cone 222 is located adjacent a bulkhead 225 of a frame 224 of the air handling section 208. The fan inlet cone 222 may be mounted to the partition wall 225. Alternatively, the frame 224 may support the fan inlet cone 222 in a suspended position adjacent to or separate from the partition wall 225. The fans 226 are mounted to drive shafts on separate respective motors 228. The motor is mounted to the frame 224 on a mounting block. Each fan 226 and corresponding motor 228 form one of the individual fan units 232 that may be housed in separate compartments 230. The chambers 230 are shown stacked vertically above each other in a column. Alternatively, more or fewer chambers 230 may be disposed adjacent to each other in a single air treatment section 208.

FIG. 2 shows a side perspective view of a column 250 of compartments 230 and the corresponding fan units 232 therein. The frame 224 includes edge beams 252 that extend horizontally and vertically along the top, bottom, and sides of each chamber 230. Side panels 254 are disposed on opposite sides of at least a portion of fan unit 232. Top and bottom panels 256 and 258 are disposed above and below at least a portion of the fan unit 232. Top and bottom panels 256 may be provided above and below each fan unit 232. Alternatively, the panel 256 may be disposed only above the uppermost fan unit 232 and/or only below the lowermost fan unit. The motor is mounted on a bracket 260 that is fixed to the edge beam 252. The fan 226 is a side-opening air delivery fan that draws air inwardly along the rotational axis of the fan and discharges the air about the rotational axis in the direction of arrow 262. The air then flows out of the discharge end of each chamber 230 in the direction of arrows 266.

The top, bottom and side panels 256, 258 and 254 have a height 255, a width 257 and a length 253, and are sized to form a chamber 230 having a predetermined volume and length. Fig. 2B shows a length 253 that substantially corresponds to the length of the fan 226 and the motor 228. Optionally, the length 253 of each chamber 230 may be longer than the length of the fan 226 and motor 228 such that the top, bottom and side panels 256, 258 and 254 may extend out of the downstream end 259 of the motor 228. For example, panels 254, 256, and 258 can extend out of downstream end 259 of motor 228 a distance represented by bracket 253A.

Fig. 3 is a schematic view of the fan unit 232 alone. The fan unit includes a fan 226 driven by a motor 228. The inlet cone 222 is coupled upstream of the fan 226 and includes a central axis 261. Fan unit 232 includes an upstream section 260 and a downstream section 262. The motor controller 264 is positioned adjacent to the motor 228. Alternatively, the motor controller 264 may be located adjacent to one of the top, bottom and side panels 256, 258 and 254, as shown in fig. 2, and/or remote from the fan unit 232.

During operation, the motor 228 rotates the fan 226 to draw air from the intake chamber 261 to the downstream zone 262 through the inlet cone 222. It should be noted that with respect to airflow, "upstream" is defined as moving from fan 226 to inlet cone 222, and "downstream" is defined as moving from inlet cone 222 to fan 226. The motor controller 264 may adjust the speed of the fan 226 to reduce or increase the amount of airflow through the fan unit 232. Noise may propagate from fan unit 232 to upstream 260 and downstream 262. The noise may include fan noise generated by vibration or friction in the fan 226 or motor 228, among other noise. The noise may also include ambient noise generated outside of the fan unit 232. Both fan noise and ambient noise include acoustic parameters of frequency, wavelength, period, amplitude, intensity, speed, and direction. The noise propagates in noise vector 266.

Fan unit 232 includes active acoustic attenuation that reduces fan noise within active cancellation zone 268. Active cancellation zone 268 is in neck 269 of inlet cone 222. Alternatively, active cancellation zone 268 may be upstream of inlet cone 222. In the exemplary embodiment, active cancellation zone 268 is located in upstream zone 260. Alternatively, active cancellation zone 268 may be located in downstream zone 262. Active acoustic attenuation can reduce one of the acoustic parameters to approximately zero using destructive interference. Destructive interference is achieved by superposition of the acoustic waveform on the original acoustic waveform to cancel the original acoustic waveform by reducing or eliminating one of the acoustic parameters of the original waveform. In an exemplary embodiment, the amplitude of the noise vector 226 is reduced or substantially eliminated. Alternatively, any of the acoustic parameters of noise vector 266 may be eliminated.

Active acoustic attenuation is enabled by source microphone 270, response microphone 272, speaker 274, and attenuation module 276. The source microphone 270 is located within the inlet cone 222. The source microphone 270 is configured to detect the noise vector 266. The step of detecting noise vector 266 includes obtaining a sound measurement having a sound parameter. For example, the sound pressure of the noise vector 266 may be obtained to determine the acoustic parameter. The source microphone 270 may be located at the junction 278 of the inlet cone 222 and the fan 226. Alternatively, the source microphone 270 may be positioned along any portion of the inlet cone 222 or upstream of the inlet cone 222. In the exemplary embodiment, source microphone 270 is positioned flush with an inner surface 280 of inlet cone 222 to reduce disturbances in the airflow through inlet cone 222. Alternatively, the source microphone 270 may extend toward the central axis 263 on the beam arm or bracket.

In an exemplary embodiment, the source microphone 270 includes a pair of microphones configured to be biased against ambient noise. Alternatively, the source microphone may comprise only one microphone. The pair of microphones includes a downstream microphone 282 and an upstream microphone 284. Optionally, the source microphone 270 may include a plurality of microphones configured to be biased against ambient noise. In one embodiment, the upstream microphone 284 may be located approximately 50mm from the downstream microphone 282. Alternatively, microphones 282 and 284 may have any suitable spacing. Further, in the exemplary embodiment, microphone 282 is located at approximately the same circumferential location as microphone 284. Alternatively, microphones 282 and 284 may be located in different circumferential locations of inlet cone 222.

Microphones 282 and 284 are biased against ambient noise so that only fan noise is attenuated. Ambient noise is detected by the upstream microphone 284 and the downstream microphone 282 substantially simultaneously. However, there is a time delay between the downstream microphone 282 that senses fan noise and the upstream microphone that senses fan noise. Thus, fan noise can be distinguished from ambient noise, and ambient noise is removed from noise vector 266.

Speaker 274 is located upstream of inlet cone 222. The speaker 274 is made of porous foam or metal. For example, speaker 274 may be fabricated from acoustically transparent foam. In one embodiment, speaker 274 has an aerodynamic shape that has a limited impact on fan performance. For example, the speaker 274 may be dome-shaped. In an exemplary embodiment, the speaker 274 is mounted on a tripod or similar support 286. Optionally, a speaker 274 may be coupled to one of the panels 254, 256, and 258 or the frame 224. In addition, speaker 274 may be located upstream of the fan unit and configured to attenuate noise throughout the fan unit. The speaker 274 is aligned with the central axis 261 of the inlet cone 222. Alternatively, the speaker 274 may be offset from the central axis 261. Speaker 274 may also be angled toward central axis 261. Speaker 274 transmits attenuation vector 288 downstream and opposite of noise vector 266. Attenuation vector 288 is an inverse noise vector 266 having the opposite phase and matching amplitude of noise vector 266. Attenuation vector 288 destructively interferes with noise vector 266 to produce attenuated noise vector 290 having an amplitude of approximately zero. Optionally, the attenuation vector 288 reduces any of the noise vector acoustic parameters such that the attenuated noise vector 290 is inaudible.

The response microphone 272 is located upstream of the source microphone 270 and within the active cancellation zone 268. The responsive microphone 272 is positioned flush along the inlet surface 280 of the inlet cone 222. Alternatively, the response microphone 272 may extend toward the central axis 261 on the beam arm or cradle. Further, a response microphone 272 may be located in the intake chamber 261 and/or upstream of the fan unit. The response microphone 272 is configured to detect the attenuated noise vector 266. Detecting the attenuated noise vector 290 includes obtaining a sound measurement having a sound parameter. For example, the sound pressure of the attenuated noise vector 290 may be obtained to determine the acoustic parameter. As described in more detail below, the attenuated noise vector is compared to noise vector 266 to determine whether noise vector 266 is reduced or eliminated.

Typically, the noise vector 266 remains dynamic throughout the operation of the fan unit 232. Therefore, attenuation vector 288 must be modified to accommodate the changes in noise vector 266. Attenuation module 276 is located within fan unit 232 to modify attenuation vector 288. Alternatively, the attenuation module 276 may be located within the air treatment system 200, or may be remote therefrom. Attenuation module 276 may be internally programmed or configured to operate software stored on a computer readable medium.

Fig. 4 is a block diagram of an attenuation module 276 electrically coupled to a source microphone 270 and a response microphone 272. Attenuation module 276 includes an amplifier 302 and an automatic gain controller 304 to alter the noise vector 266 detected by source microphone 270. Similarly, amplifier 306 and automatic gain controller 308 modify the attenuated noise vector 290 detected by response microphone 272. Codec 310 digitally encodes noise vector 266 and attenuated noise vector 290. The digital signal processor 312 obtains the acoustic parameters for each vector 266 and 290. The vectors are compared using an adaptive signal processing algorithm 314 to determine whether the noise vector 266 is attenuated. Based on this comparison, attenuation module 276 alters attenuation vector 288, which is digitally decoded by codec 310, transmitted to amplifier 316, and transmitted by speaker 274.

Fig. 5 illustrates a method 400 for active attenuation of noise vector 266. Fig. 6 is a graphical plot corresponding to active attenuation. During operation of fan unit 232, noise vector 266 propagates from fan unit 232. At 402, the source microphone 270 detects the noise vector 266. The detected noise vector 266 may include a detected sound pressure, intensity, and/or frequency of the noise vector 266. The noise vector is detected as a waveform 404, as shown in FIG. 6.

At 406, ambient noise is removed from noise vector 266. Noise vector 266 is detected by downstream microphone 282 and upstream microphone 284. The downstream microphone 282 is positioned closer to the fan 226 along the incoming airflow path than the upstream microphone 284. Thus, the downstream microphone 282 obtains the same sound measurement from the fan unit 232 a predetermined period of time before the sound measurement is obtained by the upstream microphone 284. The downstream and upstream microphones 282 and 284 sense the same sound at slightly different points in time. This time period between when the downstream and upstream microphones 182 and 284 sense the same sound is determined by the spacing or distance between the downstream and upstream microphones 282 and 284 along the airflow path. A delay corresponding to the time period may be introduced into the signal from the downstream microphone 282. At 406, the difference between the signals from the downstream and upstream microphones 282 and 284 is obtained. By adjusting this delay, the source microphone 270 is adjusted to be sensitive to sound originating from a particular direction.

Thus, at 266, ambient noise not generated by the fan unit 232 is filtered from the noise vector by setting the time delay between the downstream microphone 282 and the upstream microphone 284. The sound pressure received by the upstream microphone 284 rather than first received by the downstream microphone 282 represents ambient noise that is not generated by the fan 226. Thus, the method 400 filters out non-fan unit noise picked up by the source microphone 270. Alternatively, attenuation module 276 may ignore the signal if noise vector 266 is not within the audible range. Once the signals from microphones 282 and 284 are combined (e.g., subtracted from each other), a filtered fan unit noise signal is generated.

At 410, the filtered fan unit noise is analyzed to obtain a value of the acoustic parameter of the acoustic measurement. The acoustic parameters 411 may be calculated using an algorithm, determined using a look-up table, and/or may be predetermined and stored in the attenuation module 276. The acoustic parameters of interest may include the frequency, wavelength, period, amplitude, intensity, speed, and/or direction of the filtered fan unit noise. At 412, an attenuated signal 414 is generated. The attenuated signal 414 may be generated by inverting the waveform of the filtered fan unit noise 408. As shown in FIG. 6, the attenuated signals 414 have equal amplitudes and waveforms that are 180 degrees out of phase with the filtered fan unit noise waveforms 408.

At 416, the attenuation signal 414 is transmitted to the speaker 274 to produce an attenuation vector 288. Attenuation vector 288 is transmitted downstream in the opposite direction of noise vector 266. Attenuation vector 288 has a matched amplitude and opposite phase relative to noise vector 266. Accordingly, at 417, attenuation vector 288 destructively interferes with noise vector 266 by reducing the amplitude of noise vector 266 to approximately zero, as shown at 418 of fig. 6. It should be noted that the amplitude may be reduced to any range that is inaudible. Alternatively, attenuation vector 288 may reduce or eliminate any other acoustic parameter of noise vector 266. Further, in the exemplary embodiment, attenuation vectors 288 are timed such that noise vectors 266 are attenuated within active cancellation zone 268, thereby also eliminating noise vectors 266 upstream of active cancellation zone 268.

At 420, the attenuation of the noise vector 266 is monitored in response to the microphone 272. In an exemplary embodiment, the attenuation is monitored in real time in response to the microphone 272. As used herein, real-time refers to actively monitoring the attenuation as the attenuation vector 288 is transmitted from the speaker 274.

At 422, the attenuated noise vector 290 is detected in response to the microphone 272. At 424, attenuated noise vector 290 is compared to noise vector 266 to provide a dynamic feedback loop that adjusts and tunes attenuation vector 288.

Fig. 7 shows a fan unit 500 according to an embodiment. Fan unit 500 includes an inlet cone 502, a fan assembly 504, and a motor 506. Inlet cone 502 is located upstream of fan assembly 504. Inlet cone 502 includes a neck 508 located just upstream of fan assembly 504. It should be noted that with respect to "airflow," "upstream" is defined as moving from the fan 504 to the inlet cone 502, and "downstream" is defined as moving from the inlet cone 502 to the fan 504. The source microphone 510 is located within the neck 508 of the inlet cone 502. The source microphone 510 may include a pair of microphones. Alternatively, source microphone 510 may include only one microphone. A pair of speakers 512 is located upstream of the source microphone 510. Optionally, there may be additional speakers. A speaker 512 is located within the inlet cone 502. The speaker 512 is aerodynamically configured to limit the impact on fan performance. In one embodiment, the speakers 512 are located within the same cross-section. Alternatively, the speakers 512 may be offset from each other. A response microphone 514 is located upstream of the speaker 512. A response microphone 514 is located within the inlet cone 502. Alternatively, the response microphone 514 may be located upstream of the fan unit 500.

The noise generated by the fan 504 propagates upstream. The noise is detected by the source microphone 510. In response to the detected noise, the speaker 512 transmits an attenuated sound field configured to destructively interfere with the noise. The result of the destructive interference is detected by the response microphone 514 to provide a feedback loop to the speaker 512.

Fig. 8 shows a cross-section of an inlet cone 550 according to an embodiment. The inlet cone 550 includes a source microphone 552 and a speaker 554. The source microphone 552 and the speaker 554 are each positioned 90 degrees apart from one another. Alternatively, the source microphone 552 and speaker 554 may be positioned along any portion of the inlet cone circumference. Further, the inlet cone 550 may include a pair of source microphones 552 and/or any number of speakers 554. In the exemplary embodiment, the source microphone 552 and the speaker 554 are each located within the same cross-section of the inlet cone 550. Alternatively, the source microphone 552 and the speaker 554 may be offset from each other.

The noise propagates through the inlet cone 550. The noise is detected by source microphone 552. The speaker then produces an attenuated sound field to destructively interfere with the noise.

Fig. 9 shows a fan unit 600 according to an embodiment. Fan unit 600 includes an inlet cone 602, a fan assembly 604, and a motor 606. Inlet cone 602 is located upstream of fan assembly 604. The inlet chamber 608 is located upstream of the inlet cone 602. It should be noted that with respect to "airflow," "upstream" is defined as moving from the fan 604 to the inlet cone 602, and "downstream" is defined as moving from the inlet cone 602 to the fan 604. The source microphone 610 is located within the inlet cone 602. The source microphone 610 may include a pair of microphones. Alternatively, source microphone 610 may include only one microphone. A pair of speakers 612 is located within the intake chamber 608. Alternatively, the fan unit 600 may include any number of speakers 612. The speaker 612 is aerodynamically configured to limit the impact on fan performance. Speaker 612 is coupled to a strut 614 that extends through inlet chamber 608 and across the opening of inlet cone 602. The strut 614 and speaker 612 are angled with respect to each other. Alternatively, the struts may be curved and configured to hold any number of speakers 612.

The noise generated by the fan 604 propagates upstream. The noise is detected by source microphone 610. In response to the detected noise, the speaker 612 transmits an attenuated sound field configured to destructively interfere with the noise.

Fig. 10 illustrates an active-passive acoustic attenuation system 650 according to one embodiment. The system 650 is located within an intake chamber 652, the intake chamber 652 having an airflow 654 therethrough. The chamber 652 includes a pair of walls 656. The walls 656 are arranged in parallel. Optionally, walls 656 can be angled with respect to each other to provide converging and/or diverging chamber widths. A baffle 658 is positioned within the chamber 652. The air passages 660, 662 extend between the baffle 658 and the wall 656. In the exemplary embodiment, air channels 660, 662 have equal widths 664. Optionally, the baffles 658 may be positioned such that the widths 664 of the channels 660 and 662 are different. Baffle 658 is also positioned parallel to wall 656. Alternatively, the baffles 658 may be angled with respect to the walls 656. Further, the baffle 658 may be rounded and/or have any non-linear shape. The baffle 658 comprises an acoustic attenuation material. The sound attenuating material has a porous medium configured to absorb sound. For example, the sound attenuating material may include a fiberglass core.

A source microphone 668 is located within each wall 656. Alternatively, the source microphone 668 may be located within only one wall 656. Alternatively, the source microphone 668 may be located within the baffle 658. The source microphone 668 may be located upstream of the baffle 658, or alternatively, downstream of the baffle 658. A speaker 670 is located within the wall 656. Alternatively, only one speaker 670 may be located within the wall. The speaker 670 may also be located within the baffle 658. Speaker 670 is located downstream of source microphone 668. In one embodiment, the speaker 670 may be located downstream of the baffle 658 and configured to direct attenuated noise in a direction opposite the airflow 654.

Noise generated within the chamber 652 propagates upstream along with the airflow 654. The baffles 658 provide passive acoustic attenuation. In addition, source microphone 668 detects noise to provide active acoustic attenuation. The speaker 670 transmits acoustic attenuation noise that destructively interferes with the noise propagating through the chamber 652.

FIG. 11 is a graph 700 illustrating attenuated noise frequencies according to one embodiment. Graph 700 includes acoustic pressure (Lp) on a y-axis 702 and frequency on an x-axis 704. Seven octave bands 706 are plotted. Each octave band 706 includes a peak frequency. The peak frequencies shown are 31Hz, 63Hz, 125Hz, 250Hz, 500Hz, 1000Hz and 2000 Hz. The dominant noise component produced by the fan array typically has the same frequency as these peak frequencies. Thus, embodiments described herein are generally configured to attenuate noise propagating at the peak frequency of the octave band 706. For example, the dominant frequency component of the noise may include the blade pass frequency of the fan. The blade pass frequency is determined using the following equation:

BPF ═ (RPM of the blade #)/60

Where BPF is the blade pass frequency, RPM is the revolutions per minute of the fan, and blade # is the number of fan blades. Typically, the fan pass frequency is about 250 Hz. This frequency propagates at about 70-90 dB. It is therefore an object of the present invention to attenuate noise in the 250Hz range. Although embodiments are described with respect to attenuating noise having a peak frequency, it should be noted that the embodiments described herein are equally capable of attenuating any frequency.

FIG. 12 is a side view of an inlet cone 800 formed in accordance with an embodiment. The inlet cone 800 includes an inlet 802 and an outlet 804. In the exemplary embodiment, inlet 802 and outlet 804 have a parabolic shape. The inlet 802 has a width 806 that is greater than a width 808 of the outlet 804. The outlet 804 is configured to be positioned adjacent a fan wheel of the fan unit. In one embodiment, the outlet is coupled to a fan wheel. The intermediate portion 810 extends between the inlet 802 and the outlet 804. In the illustrated embodiment, the middle portion 810 is cylindrical in shape. In alternative embodiments, the intermediate portion 810 may have any suitable shape.

The middle portion 810 includes a plurality of apertures 812 formed therethrough. The holes 812 are formed in an array around the middle portion. The aperture 812 is configured to retain a speaker 814 (shown in fig. 13) therein. The middle portion 810 may include any suitable number of holes 812 for holding any suitable number of speakers 814. The apertures 812 may be uniformly spaced about the middle portion 810. In one embodiment, the inlet cone 800 may include holes 812 in the inlet 802 and/or the outlet 804.

Fig. 13 is a side view of a fan unit 820 formed in accordance with an embodiment. Fig. 14 is a front perspective view of the fan unit 820. The fan unit 820 includes an inlet cone 800. The inlet cone 800 is connected to a fan wheel 822 of a fan unit 820. The speaker 814 is positioned within the aperture 812 (shown as 12) of the inlet cone 800. The speakers 814 are arranged in an array around the circumference of the inlet cone 800. The speakers 814 are arranged in an array around the circumference of the middle portion 810 of the inlet cone 800.

Fig. 15 is a front perspective view of the fan unit 820, the fan unit 820 having a microphone 826 located therein. The fan wheel 822 includes an axle 824 having fan blades 828 extending therefrom. In an exemplary embodiment, the microphone assembly 832 is positioned with the hub 824 of the fan impeller 822. The microphone 826 is located within the microphone assembly 832. The illustrated embodiment includes four microphones 826 positioned in an array within a microphone assembly 832. In alternative embodiments, the fan unit 820 may include any number of microphones 826 arranged in any manner. For example, the fan unit 820 may include a single microphone 826 centered in the hub 824.

The microphone assembly 832 includes a cover 830 over the microphone 826. The cover 830 may be inserted into the hub 824 of the fan wheel 822. In an alternative embodiment, the cover 830 may abut the hub 824 of the fan wheel 822. The cover 830 may be formed of a porous material to allow sound waves to pass through it. In some embodiments, the cover 830 may be formed of foam or the like. The cover 830 restricts airflow to the microphone 826 while allowing sound waves to propagate to the microphone 826. Microphone 826 is configured to collect sound measurements from fan unit 820. In response to the sound measurement, the array of speakers 814 produces a cancellation signal.

In the illustrated embodiment, the microphone 832 is supported by a beam arm 834. The beam arm 834 holds the microphone assembly 832 within the hub 824 of the fan wheel 822. The beam arm 834 enables the fan wheel 822 to rotate while interfering with the position of the microphone assembly 832. The beam arm 834 is connected to a support beam 836 that maintains the position of the beam arm 834 and microphone assembly 832.

Embodiments described herein are described with respect to an air handling system. It should be noted that the embodiments may be used within an air handling unit and/or in an intake plenum or exhaust plenum of an air handling system. Embodiments may also be used upstream and/or downstream of the fan array within the air handling unit. Alternatively, the embodiments may be used in a clean room environment. Embodiments may be located in an exhaust chamber and/or return chute of a clean room. Alternatively, the embodiments may be used in a residential HVAC system. The embodiments can be used in the piping of a HAVC system. Alternatively, embodiments may be used with precision air control systems, DX and chilled water air handlers, data center cooling systems, process cooling systems, humidification systems, and factory-made unit controllers. Alternatively, embodiments may be used with commercial and/or residential ventilation products. Embodiments may be used in the hood and/or inlet of a ventilation product. Alternatively, embodiments may be located downstream of the inlet in the conduit and/or at the discharge.

Various embodiments described herein enable active monitoring of noise generated by a fan unit. By actively monitoring the noise, an attenuated signal is dynamically generated to cancel the noise. The attenuation signal is generated by inverting the noise signal acquired within the fan unit. Thus, attenuation is maximized by matching the amplitude of the noise signal. Further, the attenuated signal is configured to destructively interfere with noise of a range defined within the fan unit cone. As a result, the noise generated by the fan is attenuated before exiting the fan unit. Continuous feedback of the attenuation is achieved in response to the microphone, thereby facilitating dynamic changes in the system.

Various embodiments and/or components such as modules or components therein and controllers may also be implemented as part of one or more computers or processors. The computer or processor may include a computing device, an input device, a display unit, and an interface, for example, for accessing the internet. The computer or processor may include a microprocessor. The microprocessor may be connected to a communication bus. The computer or processor may also include memory. The memory may include Random Access Memory (RAM) and Read Only Memory (ROM). The computer or processor may also include a storage device, which may be a hard disk drive or a removable storage drive such as a floppy disk drive, optical disk drive, and the like. The storage device may also be other similar means for loading computer programs or other instructions into the computer or processor.

As used herein, the term "computer" or "module" may include any processor-based or microprocessor-based system, including systems using microcontrollers, Reduced Instruction Set Computers (RISC), ASICs, logic circuits, and any other circuit or processor capable of executing the functions described herein. The above examples are exemplary only, and are thus not intended to limit in any way the definition and/or meaning of the term "computer".

A computer or processor executes a set of instructions stored in one or more memory elements in order to process input data. The storage elements may also store data or other information as desired or needed. The storage element may be in the form of an information source or a physical storage element within the processing machine.

The set of instructions may include various commands that instruct the computer or processor as a processing machine to perform specific operations, such as the methods and processes of the various embodiments of the invention. The set of instructions may be in the form of a software program. The software may be in various forms, such as system software or application software. Further, the software may be in the form of a collection of separate programs or modules, a program module within a larger program, or a portion of a program module. The software may also include modular programming in the form of object-oriented programming. The processing of input data by a processing machine may be in response to operator commands, or in response to results of previous processing, or in response to a request made by another processing machine.

As used herein, the terms "software" and "firmware" are interchangeable, and include any computer program stored by a computer in memory for execution, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. With respect to the types of memory usable for storage of a computer program, the above memory types are exemplary only, and are thus not limiting.

It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the various embodiments of the invention without departing from their scope. While the dimensions and types of materials described herein are intended to define the parameters of the various embodiments of the invention, the embodiments are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of various embodiments of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "in which". Furthermore, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements on their purposes. Furthermore, the limitations of the following claims are not written in a means-plus-function format and are not intended to be interpreted according to 35u.s.c. § 112 sixth paragraph unless and until such claim limitations explicitly use the phrase "means for.

This written description uses examples to disclose various embodiments of the invention, including the best mode, and also to enable any person skilled in the art to practice various embodiments of the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of various embodiments of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if the examples have structural elements that do not differ from the literal language of the claims, or if the examples include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims (47)

1. A method for controlling noise generated by an air handling system, comprising:

collecting sound measurements from the air handling system, the sound measurements defined by acoustic parameters;

determining a value of the acoustic parameter based on the collected acoustic measurements;

calculating an offset value for the acoustic parameter, the offset value defining a cancellation signal that at least partially cancels the sound measurement; and

generating the cancellation signal based on the offset value.

2. The method of claim 1, further comprising collecting sound measurements using a microphone located in an axle of the fan wheel.

3. The method of claim 1, further comprising collecting sound measurements generated within the fan wheel.

4. The method of claim 1, further comprising generating the cancellation signal using a collection of loudspeakers positioned around the circumference of the inlet cone.

5. The method of claim 1, wherein the acoustic parameters include frequency and amplitude of the acoustic measurements, and the calculating step further comprises calculating an opposite phase and matching amplitude of the acoustic parameters.

6. The method of claim 1, further comprising:

collecting response sound measurements at the cancellation zone; and

tuning the cancellation signal based on the response acoustic parameter.

7. The method of claim 1, wherein cancelling the signal further comprises generating a cancellation signal in a direction opposite the sound measurement of the air handling system.

8. The method of claim 1 wherein the destructive signal destructively interferes with the sound measurement of the air handling system.

9. The method of claim 1, wherein the noise of the air handling system comprises a blade pass frequency of the air handling system.

10. The method of claim 1, wherein collecting sound measurements further comprises filtering ambient noise from the sound measurements.

11. The method of claim 1, wherein generating a cancellation signal further comprises generating a cancellation signal from a plurality of speakers.

12. The method of claim 1, wherein collecting sound measurements further comprises collecting sound measurements in an inlet cone of the air handling system.

13. A system for controlling noise generated by an air handling system, comprising:

a source microphone to collect sound measurements from the air handling system;

defining a module that at least partially cancels a cancellation signal of the sound measurement; and

a loudspeaker producing the cancellation signal.

14. The system of claim 13, wherein the source microphone is located in an axle of a fan impeller.

15. The system of claim 13, wherein the source microphone is supported on a beam arm that extends into an axle of a fan impeller.

16. The system of claim 13, further comprising a cover positioned over the source microphone to limit airflow to the source microphone.

17. The system of claim 16, wherein sound waves pass through the cover.

18. The system of claim 13, wherein the source microphone collects sound measurements from a fan impeller.

19. The system of claim 13, further comprising an array of speakers.

20. The system of claim 13, further comprising an array of speakers located within an inlet cone of the fan unit.

21. The system of claim 13, further comprising an array of speakers positioned around the circumference of an inlet cone of the fan unit.

22. The system of claim 13, wherein the speaker produces the cancellation signal in a direction opposite the sound measurement.

23. The system of claim 13, wherein the sound measurements are at least partially canceled in a cancellation zone, the system further comprising a response microphone collecting response sound measurements in the cancellation zone.

24. The system of claim 23 wherein the module tunes the cancellation signal based on the response sound measurement.

25. The system of claim 23, wherein the response microphone comprises a pair of microphones that filter ambient noise.

26. The system of claim 13, wherein the speaker is located in an intake chamber of the air handler.

27. The system of claim 13, wherein the speaker is located within an inlet cone of the air treatment system.

28. The system of claim 13, wherein the source microphone is located within an inlet cone of the air treatment system.

29. The system of claim 13, wherein the speaker comprises an aerodynamic surface that reduces the effect of the speaker on the performance of the air handling system.

30. The system of claim 13, further comprising a sound attenuating device that passively cancels the sound measurement.

31. The system of claim 13, further comprising a plurality of speakers.

32. A fan unit for an air handling system, comprising:

a source microphone to collect sound measurements from the air handling system;

defining a module that at least partially cancels a cancellation signal of the sound measurement; and

a loudspeaker producing the cancellation signal.

33. The fan unit of claim 32, further comprising a fan wheel, the source microphone being located in an axle of the fan wheel.

34. The fan unit of claim 32, further comprising a fan wheel, the microphone being supported on a beam arm that extends into an axle of the fan wheel.

35. The fan unit of claim 32, further comprising a cover positioned over the source microphone to limit airflow to the source microphone.

36. The fan unit of claim 32, further comprising an array of speakers.

37. The fan unit of claim 32, further comprising an inlet cone and an array of speakers positioned within the inlet cone.

38. The fan unit of claim 32, further comprising an inlet cone and an array of speakers positioned around a circumference of the inlet cone.

39. The fan unit of claim 32, wherein the speaker produces the cancellation signal in a direction opposite the sound measurement.

40. The fan unit of claim 32, wherein the sound measurements are at least partially canceled in a cancellation zone, the system further comprising a response microphone collecting response sound measurements in the cancellation zone.

41. The fan unit of claim 40, wherein the module tunes the cancellation signal based on the response sound measurement.

42. The fan unit of claim 40, wherein the response microphone comprises a pair of microphones that filter ambient noise.

43. The fan unit of claim 32, wherein the speaker is located in an intake chamber of the fan unit.

44. The fan unit of claim 32, wherein the source microphone is located within an inlet cone of the fan unit.

45. The fan unit of claim 32, wherein the speaker comprises an aerodynamic surface that reduces the effect of the speaker on the fan unit.

46. The fan unit of claim 32, further comprising a sound attenuating device that passively cancels the sound measurement.

47. The fan unit of claim 32, further comprising a plurality of speakers.