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DESCRIPTION JP2014037826

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DESCRIPTION JP2014037826
Abstract: PROBLEM TO BE SOLVED: To provide a multifunctional synthetic jet and a method of
producing the same. A synthetic jet assembly includes a synthetic jet having a cavity and a hole
formed therein. The synthetic jet assembly also includes an actuator element coupled to the back
surface of the body to selectively cause displacement of the back surface, and a control unit
electrically coupled to the actuator element. The control unit is configured to transmit a multifrequency drive signal to the actuator element, the multi-frequency drive signal including a
cooling frequency component and an acoustic frequency component superimposed on the
cooling frequency component . The cooling frequency component causes the cooling jets to drain
out of the bore in the body. The acoustic frequency component produces the desired audible
output. [Selected figure] Figure 1
Multifunctional synthetic jet and method of making same
[0001]
Embodiments of the present invention relate generally to synthetic jets, and more particularly to
multifunctional synthetic jets.
[0002]
Synthetic jet actuators are a widely used technology that produces synthetic jets of fluid to affect
the fluid flow on the surface.
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1
A conventional synthetic jet actuator comprises a housing defining an internal chamber. There is
an opening in the wall of the housing. The actuator further includes a mechanism within or
associated with the housing for periodically changing the volume in the inner chamber such that
flow is generated and expelled from the opening of the housing to the external environment. This
flow may include fluid vortices. An example of a volume change mechanism may include, for
example, a piston placed in a jet housing to move fluid in and out of the opening during
reciprocating movement of the piston or a flexible diaphragm as a wall of the housing. The
flexible diaphragm is typically moved by a piezoelectric actuator or other suitable means.
[0003]
Usually, a system is used to create the time-coordinated movement of the volume change
mechanism. As the mechanism reduces the chamber volume, fluid is drained from the chamber
through the opening. As the fluid passes through the opening, the sharp edge of the opening
separates the flow creating a swirling vortex layer. These vortices leave the edge of the opening
at their own self-induced velocity. As the mechanism increases the chamber volume, ambient
fluid is drawn into the chamber at a distance from the opening. Because the vortices are already
away from the edge of the opening, they are not affected by the surrounding fluid entering the
chamber. As the vortices leave the opening, they synthesize a jet of fluid, a "synthetic jet".
[0004]
In order to improve the heat conduction path, micro / mesoscale devices such as synthetic jets
have been proposed as potential replacements or additives for natural convection in
microelectronic devices. Applications may include the collision of fluids in and around electronics
and printed circuit boards. However, synthetic jets usually have some natural frequencies where
synthetic jets produce better cooling performance. These natural frequencies include structural
resonant frequencies. The structural resonant frequency is provided at the natural frequency of
the structure of the synthetic jet, which consists of the synthetic jet plate operating as a
collection and an elastomeric wall operating as a spring coupled with the air in the synthetic jet
volume.
[0005]
One major application of synthetic jets is in the cooling of heat producing bodies, a concern in
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many different technologies. As an example, synthetic jets can be used for thermal management
of tight spaces where the electrons can be stored and the space for the electrons is of high
quality. Typically, wireless communication devices such as cell phones, pagers, dual purpose
transceivers, etc. have much of their heat generated in integrated circuits (ie, IC) packages
located in such tight spaces. Because of the limited space therein and the limited natural
convection, the heat generated is usually conducted to the printed circuit board and then
conducted to the inner wall of the housing via conduction, convection and radiation processes.
The heat is then conducted to the surrounding environment, usually via the housing wall. The
process is usually limited due to the limited opportunity of convective cooling in the housing and
through the printed circuit board. The low temperature conductivity of printed circuit boards
based on fiberglass epoxy resins can result in high temperature resistance between the heat
source and the surrounding environment. And with the advent of smaller enclosures, faster
digital clock speeds, more power emitting devices, higher power density components, and higher
expectations for reliability, the issue of thermal management is a field of microelectronics
applications. It is becoming more and more difficult.
[0006]
Typical electronic devices and integrated circuit packages include many components for
achieving their desired functions, such as cooling devices, microphones, speakers, control
circuits, memory devices, and the like. While the use of synthetic jets via alternative cooling
devices such as air cooling fans saves space in the IC package, advances in IC packaging are
driven by the increasing need for further miniaturization of electronic packaging and its
components .
[0007]
Thus, there is a need for a simplified method and apparatus for providing integrated circuit
cooling while minimizing the overall size and complexity of the electronic device.
[0008]
U.S. Patent No. 8076822
[0009]
According to one aspect of the present invention, a synthetic jet assembly includes a synthetic jet
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having a cavity and a hole formed therein, and an actuator element coupled to the back of the
body to selectively cause displacement of the back. And a control unit electrically coupled to the
actuator element.
The control unit is configured to transmit a multi-frequency drive signal to the actuator element,
the multi-frequency drive signal including a cooling frequency component and an acoustic
frequency component superimposed on the cooling frequency component.
The cooling frequency component causes the cooling jets to exit the bore of the body. The
acoustic frequency component produces the desired audible output.
[0010]
According to another aspect of the present invention, a method of fabricating a synthetic jet
assembly includes the steps of providing a synthetic jet body surrounding a volume, forming an
opening in the synthetic jet body to gas outside the volume. Fluidly coupling the volume,
coupling the actuator element to the flexible surface of the synthetic jet body, and electronically
coupling the controller assembly to the actuator element. The controller assembly generates a
first drive signal comprising an inaudible frequency component that causes a cooling jet to be
emitted from the opening and a second drive signal comprising an audio frequency component
that produces a desired acoustic output And the first and second drive signals are combined to
form a combined drive signal, and the combined drive signal is programmed to be transmitted to
the actuator element.
[0011]
According to yet another aspect of the invention, an electronic device includes a housing having
an opening formed therein for drawing fluid from the outside of the housing into the cavity of
the housing and for discharging a cooling jet therefrom. A synthetic jet including a piezoelectric
actuator coupled to the housing. The electronic device is also cooled by a drive unit configured to
drive the piezoelectric actuator, a control unit configured to transmit a multi-frequency drive
signal to the drive unit, and the cooling jet. Includes configured electronic components. The
multi-frequency drive signal includes a cooling frequency component selected to generate the
cooling jet, and a frequency component selected to generate an audible acoustic output.
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[0012]
Various other features and advantages will be made apparent from the following detailed
description and the drawings.
[0013]
The drawings illustrate embodiments contemplated herein to practice the present invention.
[0014]
FIG. 1 is a perspective view of a synthetic jet assembly according to an embodiment of the
present invention.
FIG. 5 is a cross-sectional view of a portion of a synthetic jet according to an embodiment of the
present invention.
FIG. 3 is a cross-sectional view of the synthetic jet of FIG. 2 showing the jet as the control system
advances the diaphragm inwards towards the opening; FIG. 3 is a cross-sectional view of the
synthetic jet actuator of FIG. 2 showing the jet as the control system advances the diaphragm
outward from the opening; FIG. 5 is a block schematic diagram of a control system and synthetic
jet according to an embodiment of the present invention. FIG. 3 is a frequency diagram of an
exemplary drive signal of the synthetic jet of FIG. 2 according to an embodiment of the present
invention. FIG. 5 is a block diagram of a control system and synthetic jet according to another
embodiment of the present invention.
[0015]
Embodiments of the present invention relate to piezo-motive devices and methods of making and
using piezo-motor devices to simultaneously generate fluid jets and desired audio output. The
operating environment is described herein in terms of a thermal management system to enhance
convection in the cooling of electrons. However, it will be understood by those skilled in the art
that embodiments of the present invention are equally applicable for use in other synthetic jet
applications. For example, synthetic jets are commonly used for stand point flow control, thrust
vectoring of jets, triggering turbulence in boundary layers, and other heat transfer applications.
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Thermal conduction applications may include direct impingement of vortex dipoles on the
heating surface and the use of synthetic jets to enhance the performance of existing cooling
circuits. Thus, although embodiments of the invention are described with respect to the cooling
of electrons, they are equally applicable to systems and applications that use synthetic jets for
other purposes.
[0016]
Referring to FIG. 1, a perspective view of a synthetic jet assembly 10 is provided. The synthetic
jet assembly 10 includes a synthetic jet 12 whose mounting section is shown in FIG. 2 and a
mounting device 14. In one embodiment, the mounting device 14 is a u-shaped bracket attached
to the housing 16 of the synthetic jet 12 at one or more locations. The circuit driver 18 can be
external or attached to the mounting device 14. Alternatively, the circuit driver 18 can be located
remotely from the synthetic jet assembly 10.
[0017]
With reference both to FIGS. 1 and 2, the housing 16 of the synthetic jet 12 defines or partially
encloses an internal chamber or cavity 20 having a gas or fluid 22 therein. Although the housing
16 and the interior chamber 20 can take substantially any geometric configuration according to
various embodiments of the present invention, for purposes of discussion and understanding, the
housing 16 is a spacer element placed therebetween It is shown in the cross-sectional view of
FIG. 2 as including a first plate 24 and a second plate 26 held in spaced relation by 28. In one
embodiment, the spacer elements 28 maintain a spacing of about 1 mm between the first and
second plates 24, 26. One or more openings 30 are provided between the first and second plates
24, 26 and the sidewall of the spacer element 28 to place the inner chamber 20 in fluid
communication with the surrounding, external environment 32. It is formed. In one alternative
embodiment, spacer element 28 includes a front surface (not shown) in which one or more
openings 30 are formed.
[0018]
According to various embodiments, the first and second plates 24, 26 may be formed of metal,
plastic, glass, and / or ceramic. Similarly, spacer element 28 may be formed of metal, plastic,
glass and / or ceramic. Suitable metals include materials such as nickel, aluminum, copper and
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molybdenum or alloys such as stainless steel, brass, bronze and the like. Suitable polymers and
plastics include thermoplastics such as polyolefins, polycarbonates, thermosetting resins, epoxies,
urethanes, acrylics, silicones, polyimides, and photoresist materials, as well as other elastomeric
plastics. Suitable ceramics include, for example, titanates (such as lanthanum titanate, bismuth
titanate, and lead zirconate titanate) and molybdate salts. Additionally, various other components
of the synthetic jet 12 may be formed of metal as well.
[0019]
The actuators 34, 36 have first and second composite structures or flexible diaphragms 38, 40
controlled by the driver 18 via the controller assembly or control unit system 42, respectively. It
is coupled to the second plate 24, 26. As shown in FIG. 1, in one embodiment, the controller
assembly 42 is electronically coupled to a driver 18 that is directly coupled to the mounting
bracket 14 of the synthetic jet 12. In an alternative embodiment, control unit system 42 is
integrated into driver 18 located remotely from synthetic jet 12. For example, each flexible
diaphragm 38, 40 can comprise a metal layer, such that the diaphragm 38, 40 can be moved
through such an electrical bias between the electrode and the metal layer, and A metal electrode
may be disposed adjacent to the metal layer. Further, control system 42 may be configured to
generate the electrical bias by any suitable device such as, for example, a computer, a logic
processor, or a signal generator.
[0020]
In one embodiment, the actuators 34, 36 are piezoelectric motive devices that can be actuated by
the application of a harmonic alternating voltage that causes the piezoelectric motive devices to
expand and contract rapidly. In operation, control system 42 transmits electrical charge to
piezoelectric actuators 34, 36 via driver 18, and piezoelectric actuators 34, 36 experience
mechanical stress and / or strain in response to the electrical charges. The stress / strain of the
piezoelectric motor actuators 34, 36 results in the deflection of the first and second plates 24,
26, respectively, such that time coordinated or periodic motion is achieved. The resulting volume
change in the inner chamber 20 results in the exchange of gas or other fluid between the inner
chamber 20 and the outer volume 32, as will be described in detail with respect to FIGS.
[0021]
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According to various embodiments of the present invention, piezoelectric motor actuators 34, 36
may be monomorph or bimorph devices. In one embodiment of the monomorph, the piezoelectric
motor actuators 34, 36 may be coupled to plates 24, 26 formed of a material comprising metal,
plastic, glass or ceramic. In one bimorph embodiment, one or both of the piezoelectric motor
actuators 34, 36 may be bimorph actuators coupled to plates 24, 26 formed of piezoelectric
material. In one alternative embodiment, the bimorph can include a single actuator 34, 36 and
the plates 24, 26 are a second actuator.
[0022]
The components of the synthetic jet 12 may be glued or otherwise attached to one another using
an adhesive, solder or the like. In one embodiment, a thermoset or conductive adhesive is used to
bond the actuators 34, 36 to the first and second plates 24, 26 so that the first and second
composites Form structures 38, 40. In the case of a conductive adhesive, the adhesive may be
filled with a conductive filler such as silver, gold or the like to affix a lead (not shown) to the
synthetic jet 12. Suitable adhesives can have a hardness in the range of Shore A hardness 100 or
less, and can include, by way of example, silicone, polyurethane, thermoplastic rubber, etc., such
that an operating temperature of 120 degrees or more can be achieved.
[0023]
In one embodiment of the present invention, actuators 34, 36 may include devices other than
piezoelectric motivation devices, such as hydraulic, pneumatic, magnetic, electrostatic and
ultrasonic materials. Thus, in such embodiments, control system 42 is configured to activate
actuators 34, 36, respectively, in a corresponding manner. For example, if an electrostatic
material is used, the control system 42 provides a rapid alternating electrostatic voltage to the
actuators 34, 36 to activate and move the first and second plates 24, 26, respectively. Can be
configured.
[0024]
The operation of the synthetic jet 12 is described with reference to FIGS. 3 and 4. Referring first
to FIG. 3, the synthetic jet 12 is controlled such that the actuators 34, 36 move the first and
second plates 24, 26 outward with respect to the inner chamber 20, as indicated by the arrow
44. As shown. As the first and second plates 24, 26 move outward, the interior volume of the
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interior chamber 20 increases and the surrounding fluid or gas 46 drips into the interior
chamber 20 as indicated by the set of arrows 48. The actuators 34, 36 are such that when the
first and second plates 24, 26 move outward from the inner chamber 20, the vortices have
already been removed from the edge of the opening 30 and thus the ambient fluid drawn into the
inner chamber 20. It is controlled by control system 42 so as not to be influenced by 46. On the
other hand, the jet of ambient fluid 46 is synthesized by the vortices that create a strong
entrainment of ambient fluid 46 drawn from far away from the opening 30.
[0025]
FIG. 4 shows the synthetic jet 12 as the actuators 34, 36 are controlled to move the first and
second plates 24, 26 inside the interior chamber 20, as indicated by the arrows 50. As the
internal volume of the inner chamber 20 decreases, the fluid 22 flows as a cool air jet through
the opening 30 in the direction indicated by the set of arrows 52 towards the device to be cooled,
for example a light emitting diode Exhausted. As fluid 22 exits inner chamber 20 through
opening 30, the flow swirls and creates a vortex layer that begins to move away from the edge of
opening 30.
[0026]
Although the synthetic jets of FIGS. 1-4 are illustrated and described as having a single opening
therein, it is also envisioned that embodiments of the present invention may include multipleopening synthetic jet actuators. . Additionally, although the synthetic jet actuators of FIGS. 1-4
are illustrated and described as having actuator elements included in each of the first and second
plates, embodiments of the present invention may It is also envisioned that it may include only a
single actuator element placed on one of the plates. Furthermore, it is also envisioned that the
synthetic jet plate may be provided in a circular, rectangular or other shaped configuration
rather than the square configuration as shown herein.
[0027]
Referring now to FIG. 5, a block diagram of the synthetic jet 12 and control system 42 is
provided in accordance with one embodiment of the present invention. In operation, control
system 42 is programmed to transmit multi-frequency drive signal 56 to actuators 34, 36 (FIG.
2) of synthetic jet 12. The multi-frequency drive signal 56 is generated from the combination of
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the cooling frequency drive signal used to generate the cooling jet and the acoustic frequency
drive signal 60 used to generate the desired audio output It is a drive signal.
[0028]
The drive signals 58, 60 are combined by a controller 62 in which digital signal processing (DSP)
algorithms are stored. The controller 62 receives the cooling and acoustic frequency drive signals
58, 60 to generate a multi-frequency drive signal 56 having a cooling frequency component from
the drive signal 58 and an acoustic frequency component from the drive signal 60, the DSP Input
the signal to the algorithm. The cooling frequency component of the multi-frequency drive signal
56 expands and contracts the synthetic jet 12 in a manner that produces the desired jet for
cooling purposes. In one embodiment, the cooling frequency component ACs the synthetic jet 12
at a frequency that is not detectable or substantially undetectable by the human ear, such as, for
example, between about 10 and 400 Hz or alternatively above 20000 Hz. Apply voltage. The
acoustic frequency component of the multi-frequency drive signal 56 causes the synthetic jet 12
to produce an audible acoustic output that is detectable by, for example, the human ear.
According to various embodiments, the acoustic frequency component can apply an AC voltage
at one or more frequencies between about 500 and 20000 hertz. As shown in detail in FIG. 6, the
acoustic frequency components of the multi-frequency drive signal 56 can be superimposed on
the cooling frequency components. Thus, the multi-frequency drive signal 56 produces
simultaneous cooling and audible acoustic output.
[0029]
Referring back to FIG. 5, the control system 42 generates a multi-frequency drive signal 56 that
drives the synthetic jet 12 in one of the audio output mode or the noise removal mode while
maintaining the drive frequency for cooling. Do. As used herein, the audio output mode indicates
an operating mode in which the audio frequency component causes the synthetic jet 12 to
generate the desired audible audio output, such as, for example, an oral announcement, an alert,
a server message, or a music output. . As used herein, the denoising mode indicates an operating
mode that causes the synthetic jet 12 to generate a desired audible acoustic output that
eliminates or reduces unwanted ambient noise conditions.
[0030]
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When operating in an audio output mode, the drive elements 34, 36 of the synthetic jet 12 are
driven to produce an acoustic output that can be used for audio applications in devices equipped
with synthetic jets for cooling operation. Do. Thereby, the synthetic jet 12 acts as both a cooling
device and a speaker. In one such embodiment, in addition to providing active cooling, the
synthetic jet 12 may, for example, provide an audible alert to construct an announcement to
simultaneously function as a speaker in a consumer electronic device such as a cell phone. It may
be used in any number of applications, including as an alternative to output or provide a
message, or to generate environmental music in a lighting application. In the audio output mode,
the acoustic frequency component may include, for example, one or more frequencies in the
range of about 500 to 4000 Hertz.
[0031]
In one embodiment of the denoising mode, the control system 42 is preprogrammed with an
acoustic anti-noise drive signal 60 corresponding to the frequency of one or more known sounds
of unwanted environmental noise or ambient noise conditions. . For example, anti-noise drive
signal 60 may be selected to remove audible acoustic noise generated by an engine, fan, or other
noise generating device placed in proximity to synthetic jet 12. In one such embodiment, antinoise drive signal 60 is produced by phase shifting ambient noise, for example by generating
anti-noise drive signal 60 approximately 180 degrees out of phase with ambient noise. . The
synthetic jet 12 can provide cooling simultaneously while providing noise protection.
[0032]
Referring now to FIG. 7, a block schematic diagram of the synthetic jet 12 and control system 42
is shown in accordance with the present invention, in which the control system 42 controls the
synthetic jet 12 in an alternative embodiment of the noise removal mode. It is configured to
drive. In such a mode, the control system 42 uses the acoustic drive signal to simultaneously
eliminate or reduce the measured or recorded ambient noise while providing cooling, as
described in more detail below, to generate noise suppression. Drive the drive elements 34, 36
(FIG. 2) of the synthetic jet 12 at acoustic frequencies.
[0033]
One or more sound detection units 64, such as microphones, are used to measure / record
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ambient acoustic noise 66. The digital signal 68 corresponding to the measured / recorded noise
66 is output to a controller 70 in which a digital signal processing (DSP) algorithm is stored. The
controller 70 drives the anti-noise drive with an appropriate frequency and phase at which antinoise protection should be generated by the synthetic jet 12, such as, for example, one or more
frequencies shifted about 180 degrees from the phase of the detected noise To determine signal
72, an output is received from one or more microphones 64 and input to a DSP algorithm. In one
embodiment, the anti-noise drive signal 72 may be determined based on the identified frequency
above or below a predetermined threshold. Furthermore, the anti-noise drive signal 72 may be
used to actually shift the frequency or given frequency spectrum of one or more sounds.
[0034]
In a manner similar to that described with respect to FIG. 5, the controller 62 then combines the
anti-noise drive signal 72 with the cooling frequency drive signal 58 for cooling purposes to
provide a cooling frequency component and drive signal corresponding to the drive signal 58. A
multi-frequency drive signal 74 is generated having acoustic frequency components
corresponding to 72. The drive elements 34, 36 (FIG. 2) are then used to reduce the frequency of
the desired cooling frequency and that of the corresponding ambient acoustic noise, but out of
phase, to reduce or eliminate unwanted ambient noise. The synthetic jet 12 is driven by both.
Thus, with controller operation of the synthetic jet 12 by means of the DSP algorithm of the
controller 62, 70, the synthetic jet 12 can actively generate anti-noise protection at multiple
different sound frequencies while maintaining active cooling it can.
[0035]
Although the waveforms of the various drive signals described herein are shown as sine waves,
the drive signals are not limited to particular waveforms, and sine waves, square waves, triangle
waves, or any other suitable It should be understood that it may be provided as a waveform.
[0036]
Thus, in accordance with one embodiment of the present invention, a synthetic jet assembly has
a synthetic jet having a cavity and a hole formed therein, the synthetic jet assembly being
coupled to the back of its body to selectively provide back side displacement. An actuator
element and a control unit electrically coupled to the actuator element.
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The control unit is configured to transmit to the actuator element a multi-frequency drive signal
comprising a cooling frequency component and an acoustic frequency component superimposed
on the cooling frequency component. The cooling frequency component causes the cooling jets
to exit the bore of the body. The acoustic frequency component produces the desired audible
output.
[0037]
According to another embodiment of the present invention, a method of fabricating a synthetic
jet assembly includes the steps of providing a synthetic jet body surrounding a volume, forming
an opening in the synthetic jet body to provide gas outside the volume. Fluidly coupling the
volume, coupling the actuator element to the flexible surface of the synthetic jet body, and
electronically coupling the controller assembly to the actuator element. The controller assembly
generates a first drive signal comprising an inaudible frequency component that causes a cooling
jet to be emitted from the opening and a second drive signal comprising an audio frequency
component that produces a desired acoustic output. And the first and second drive signals are
combined to form a combined drive signal, and the combined drive signal is programmed to be
transmitted to the actuator element.
[0038]
According to yet another embodiment of the present invention, an electronic device has a
housing formed therein for taking fluid from the outside of the housing into the cavity of the
housing and discharging the cooling jet therefrom. And a piezo-electric actuator coupled to the
housing. The electronic device is also cooled by a drive unit configured to drive the piezoelectric
actuator, a control unit configured to transmit a multi-frequency drive signal to the drive unit,
and the cooling jet. Includes configured electronic components. The multi-frequency drive signal
includes a cooling frequency component selected to generate the cooling jet, and a frequency
component selected to generate an audible acoustic output.
[0039]
This written description, including the best mode, is given to the person skilled in the art for
disclosing the invention, and also for making and using any device or system and performing any
incorporated method. Use an example to make it executable. The patentable scope of the
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invention is defined by the claims, and may include other examples that occur to those skilled in
the art. Such other examples are equivalent if they have structural elements that do not differ
from the literal language of the claims, or they are equivalent with only a slight difference from
the literal language of the claims. When including the structural elements of (1), it shall be within
the scope of the present claims.
[0040]
10 synthetic jet assembly 12 synthetic jet 14 mounting device 16 housing 18 circuit driver 20
internal chamber 22 fluid 24 first plate 26 second plate 28 spacer element 30 opening 32
external environment 34 actuator 36 actuator 38 diaphragm 40 diaphragm 42 Control unit
system 46 Ambient fluid 56 Multi frequency drive signal 58 Cooling frequency drive signal 60
Acoustic frequency drive signal 62 Controller 64 Sound detection unit 66 Ambient acoustic noise
68 Digital signal 70 Controller 72 Anti-noise drive signal
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