Acoustically intelligent windows

Description of equivalent WO 2004051623 A1

ACOUSTICALLY INTELLIGENT WINDOWS

TECHNICAL FIELD

The present invention relates generally to the field of windows and, in particular, to noise transmission, noise reduction, and acoustic control in windows. BACKGROUND

Windows normally include one or more transparent panels (or panes), e.g., of glass, plastic, or the like. Windows are used in buildings, automobiles, airplanes, etc. for admitting light while protecting against heat loss or gain, moisture loss or gain, noise, or the like. One problem with many windows is that they do not always provide adequate protection against noise. To this end, techniques have been developed for reducing sound transmission through windows.

One technique for reducing sound transmission through a window involves a double-paned window with each of the panes having a different thickness for blocking out noise over a broader range of frequencies than two-paned windows with panes having the same thickness. Another technique involves a two-paned window with each of the panes having a different density for blocking out noise over a broader range of frequencies than two-paned windows with panes having the same density. For some techniques, a vibration dampening material is disposed between two windowpanes of different thickness and/or density for dampening vibrations of either windowpane. One problem with these techniques for reducing sound transmission through windows is that they usually require increased frame sizes and more glass compared to conventional two-paned windows, which results in increased costs. Also, these techniques may result in relatively heavier windows and thus may be more difficult to install than conventional windows. Moreover, these techniques are limited to two-paned windows. Another technique for reducing sound transmission through a window involves laminated windowpanes for reducing sound transmission. However, laminated windowpanes are more expensive than non-laminated windows, e.g., usually about 30 to 60 percent more expensive. Moreover, laminated windows and two-paned windows having panes of different density may alter optical properties of the window. For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative noise suppressing windows.

SUMMARY One embodiment of the present invention provides a window having a frame with a windowpane disposed therein. A first impedance discontinuity element is disposed between the windowpane and the frame adjacent a portion of a periphery of the windowpane. A second impedance discontinuity element is disposed adjacent another portion of the periphery of the windowpane. The first and second impedance discontinuity elements have different impedances.

Another embodiment of the present invention provides a window having a frame. A plurality of windowpanes is disposed within the frame. Each of the plurality of windowpanes is substantially parallel to another of the plurality of windowpanes, and each of the plurality of windowpanes is separated from another of the plurality of windowpanes by a gap. First and second impedance discontinuity elements are disposed adjacent a periphery of each of the plurality of windowpanes. The first and second impedance discontinuity elements have different impedances. The first and second impedance discontinuity elements of adjacent windowpanes of the plurality of windowpanes are staggered relative to one another.

Another embodiment of the present invention provides a window having a frame with a windowpane disposed therein. A passive impedance discontinuity element is disposed adjacent a portion of a periphery of the windowpane. An active impedance discontinuity element is disposed between the windowpane and the frame adjacent another portion of the periphery of the windowpane. The active impedance discontinuity element is activated so that the active and passive impedance discontinuity elements have different impedances. Another embodiment of the present invention provides a window having a frame with a windowpane disposed therein. An actuator is disposed between the windowpane and the frame adjacent a periphery of the windowpane. A sensor is disposed between the windowpane and the frame adjacent the periphery of the windowpane. The window also includes a controller having an input electrically coupled to the sensor and an output electrically coupled to the actuator. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view illustrating a section of a window according to an embodiment of the present invention.

Figure 2 is a perspective view illustrating a distribution of impedance discontinuity elements around windowpanes of the window of Figure 1 according to another embodiment of the present invention.

Figure 3 illustrates discrete impedance discontinuity elements distributed around a windowpane according to another embodiment of the present invention.

Figure 4 illustrates discrete impedance discontinuity elements distributed around a windowpane according to yet another embodiment of the present invention.

Figure 5 is a cross-sectional view illustrating an embodiment of an impedance discontinuity element of the present invention.

Figure 6 is a cross-sectional view illustrating another embodiment of an impedance discontinuity element of the present invention. Figures 7A, 7B, and 8 illustrate other embodiments of impedance discontinuity elements of the present invention.

Figure 9 is a cross-sectional view illustrating another embodiment of a impedance discontinuity element of the present invention.

Figure 10 illustrates a control apparatus according to another embodiment of the present invention.

Figures 11 A and 1 IB respectively illustrate vibration energy distributions within a conventional windowpane and a windowpane having impedance discontinuities according to an embodiment of the present invention.

Figure 12 is a flowchart of a method for controlling sound radiation from a window according to another embodiment of the present invention.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific illustrative embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. Sound waves impinging on a windowpane cause the windowpane to vibrate. The vibrating windowpane radiates sound at a sound pressure level (SPL) that increases with increasing vibration energy of the windowpane. In addition, radiated sound from a windowpane depends on the distribution of vibration energy within the windowpane and frame structures. Therefore, decreasing the vibration energy of a vibrating windowpane or modifying the vibration energy distribution can reduce sound radiation from the windowpane. Distribution of vibration energy within a vibrating windowpane depends upon conditions at boundaries (or a periphery) of the windowpane. That is, the vibration energy and its distribution within a vibrating windowpane depend upon the way the windowpane is supported at its periphery. Embodiments of the present invention provide "acoustically intelligent windows" that have impedance (or stiffness) discontinuities at a periphery of a windowpane that act to modify a vibration energy distribution within the windowpane when the windowpane vibrates due to impinging sound waves. In some embodiments, the impedance discontinuities act reduce the vibration energy of the windowpane. The impedance discontinuities at the periphery of the windowpane can be produced by passive and/or active impedance discontinuity elements that for one embodiment act to reduce the vibration energy through energy management, e.g., redistributing the vibration energy within the windowpane, and energy dissipation. In various embodiments, an impedance discontinuity element is anything that creates an elasticity change in a material or a structure. Figure 1 is a perspective view illustrating a section of a window 100 according to an embodiment of the present invention. Window 100 includes a frame 130. Windowpanes 1 10| and 1 10₂ are disposed within frame 130 so that windowpane I 10₍ is substantially parallel to windowpane 1 10 . Windowpanes 1 10| and 1 10₂ are separated by a gap 120, e.g., filled with a gas, such as air, neon, argon, or the like. In one embodiment, frame 130 includes slots 152 and 154. Impedance discontinuity elements 162 and 164 that have different impedances (or resistances to motion) are respectively disposed within slots 152 and 154 adjacent a periphery 140 of each of windowpanes 1 10ι and 1 10₂. Impedance discontinuity element 162 forms an interface between windowpane 1 10ι and frame 130, while impedance discontinuity element 164 forms an interface between windowpane 1 10₂ and frame 130. Impedance discontinuity elements 162 and 164 respectively contact windowpanes 1 10] and 1 10₂ adjacent a periphery 140 of each of windowpanes 1 10ι and 1 10₂ and support windowpanes 1 10] and 1 10₂ within frame 130. In one embodiment, either impedance discontinuity element 162 or 164 is frame 130 or is of the same material as frame 130.

Figure 2 is a perspective view that illustrates a distribution of impedance discontinuity elements 162 and 164 around periphery 140 of windowpanes 1 10| and 1 10₂ according to another embodiment of the present invention. Impedance discontinuity element 162 is disposed around a portion of periphery 140 of windowpane 1 10], while impedance discontinuity element 164 is disposed around another portion of periphery 140 of windowpane 1 10]. This creates impedance discontinuities 210 adjacent periphery 140 of windowpane 1 10i. Impedance discontinuity element 162 is also disposed around a portion of periphery 140 of windowpane 1 10₂, while impedance discontinuity element 164 is disposed around another portion of periphery 140 of windowpane 110₂. This creates stiffness discontinuities 220 at periphery 140 of windowpane 1 10₂. In one embodiment, impedance discontinuity elements 162 and 164 of windowpane 1 10] are staggered relative to impedance discontinuity elements 162 and 164 of windowpane 1 10₂, as illustrated in Figures 1 and 2, so as to create an impedance discontinuity between windowpanes 1 10| and 1 10₂. While Figure 1 illustrates a window with two windowpanes, the number of windowpanes is not limited to two. Rather, the window can have any number of windowpanes, including a single windowpane.

Impedance discontinuity elements 162 and 164 are not limited to continuous elements, as illustrated in Figures 1 and 2. Instead, in another embodiment, impedance discontinuity elements 162 and 164 are discrete elements disposed along one or more portions of periphery 140 of each of windowpanes 1 10| and 1 10₂. Figure 3 shows that for one embodiment, one or more impedance discontinuity elements 162 are disposed along opposing edges 302 and 304 of a windowpane 1 10, and one or more impedance discontinuity elements 164 are disposed along opposing edges 306 and 308 of the window 1 10 that are located between opposing edges 302 and 304. Figure 4 shows that for another embodiment, an impedance discontinuity element 162 is disposed along each of boundaries 302, 304, 306, and 308, of a windowpane 1 10, and an impedance discontinuity element 164 is disposed at each of corners 410 of the windowpane 1 10. Placement of impedance discontinuity elements 162 and 164 is not limited to the placements illustrated in Figures 2-4. For example, one or more impedance discontinuity elements 162 and one or more impedance discontinuity elements 164 can be located opposite each other, e.g., respectively along opposing edges 302 and 304, etc., or in other patterns.

In one embodiment, impedance discontinuity elements 162 and 164 are passive impedance discontinuity elements, e.g., impedance discontinuity elements 162 and 164 can be a solid of steel, an elastomer, wood, etc., a spring, such as coil, leaf, ring, plate, etc., or the like, as long as impedance discontinuity elements 162 and 164 are of different stiffness. For example, in one embodiment, impedance discontinuity element 162 is a steel solid, while impedance discontinuity element 164 is a wood solid, an elastomeric solid, a spring, or the like. In another embodiment, impedance discontinuity elements 162 and 164 are springs of different stiffness. In some embodiments, impedance discontinuity elements 162 and 164 are holes, slots, notches, or the like in portions of frame 130 for changing the elasticity in the respective portions of the frame. In one embodiment, discontinuity elements 162 and 164 are a damping material, e.g., a viscoelastic material.

In other embodiments, impedance discontinuity elements 162 and 164 are active impedance discontinuity elements (or actuators). In one embodiment, impedance discontinuity elements 162 and 164 are piezoelectric actuators comprising a formulation of lead, magnesium, and niobate (PMN), a formulation of lead, zirconate, and titanate (PZT), or the like. Piezoelectric construction and operation are well known to those in the art. A detailed discussion, therefore, of specific constructions and operation is not provided herein. It will be appreciated that when a voltage is applied to piezoelectric actuators deployed as impedance discontinuity elements 162 and 164, impedance discontinuity elements 162 and 164 impart a force to a windowpane 1 10 and to a frame 130. In one embodiment, the force produces impedance (or resistance to motion) between a windowpane 1 10 and frame 130. Applying different voltages to piezoelectric actuators deployed as impedance discontinuity elements 162 and 164 causes impedance discontinuity elements 162 and 164 to produce different impedances.

For one embodiment, impedance discontinuity elements 162 and 164 include piezoelectric layers 500ι to 500_N separated by electrodes 502, e.g., of metal, as illustrated in Figure 5, a cross-sectional view of a portion of window 100. For another embodiment, impedance discontinuity elements 162 and 164 include a substrate 600 having a number of piezoelectric elements 650 disposed within substrate 600, as illustrated in Figure 6, a cross- sectional view of a portion of window 100. For some embodiments, piezoelectric elements 650 are piezoelectric rods, piezoelectric tubes, a number of piezoelectric layers, etc.

For other embodiments, impedance discontinuity elements 162 and 164 are piezoelectric benders that operate similarly to a bimetallic strip in a thermostat. For another embodiment, impedance discontinuity elements 162 and 164 are configured as a laminar piezoelectric actuator comprising parallel piezoelectric strips. The displacement of these actuators is perpendicular to the direction of polarization and the electric field. The maximum travel is a function of the length of the strips, and the number of parallel strips determines the stiffness and stability of the element.

In another embodiment, impedance discontinuity elements 162 and 164 include piezoelectric sensor 710 and a piezoelectric actuator 720, as generally illustrated in Figures 7A and 7B. In one embodiment, piezoelectric sensor 710 and piezoelectric actuator 720 are integral. In some embodiments, piezoelectric sensor 710 and piezoelectric actuator 720 are stacked substantially parallel to a windowpane 1 10 and frame 130, as shown in Figure 7 A. That is, piezoelectric sensor 710 and piezoelectric actuator 720 each contact the windowpane 1 10 and frame 130. In other embodiments, piezoelectric sensor 710 and piezoelectric actuator 720 are collocated (or stacked substantially perpendicular to a windowpane 1 10 and frame 130, as shown in Figure 7B). That is, piezoelectric sensor 710 is disposed between piezoelectric actuator 720 and frame 130, while piezoelectric actuator 720 is disposed between piezoelectric sensor 710 and the windowpane 1 10.

When a voltage Vin is applied to piezoelectric actuator 720, it imparts a force to a windowpane 1 10 and frame 130 that produces an impedance discontinuity between the windowpane 1 10 and frame 130. Conversely, when a windowpane 1 10 imparts a vibratory motion or a force to piezoelectric sensor 710, either directly for the embodiment of Figure 7 A or indirectly via piezoelectric actuator 720 for the embodiment of Figure 7B, piezoelectric sensor 710 produces voltage Vout that is indicative of the vibratory motion or force. In another embodiment, impedance discontinuity elements 162 and 164 are actuators formed from shape memory alloys (SMAs). SMAs are materials that have an ability to return to their original shapes through a phase transformation that can take place by inducing heat in the SMA materials. When an SMA is below its transformation temperature, it has very low yield strength and can be easily deformed into a new shape (which it will retain). However, when an SMA is heated above its transformation temperature, it will return to the original shape. If the SMA encounters any resistance during this transformation, it can generate large forces. The most common and useful shape memory materials are Nickel- titanium alloys called Nitinol (Nickel Titanium Naval Ordnance Laboratory).

In one embodiment, impedance discontinuity elements 162 and 164 are leaf springs formed from SMA foils 810 and 820, as shown in Figure 8, with a relatively large stroke. In one embodiment, clamps 830 and 840 terminate SMA foils 810 and 820, e.g., in a packing density of 40 leaf springs per square inch. When a control current Ic is applied to a leaf spring, the control current produces heat that heats SMA foils 810 and 820, in one embodiment, above their transformation temperature. In one embodiment, this causes foils 810 and 820 to move in a direction indicated by arrows 850 in Figure 8. In other embodiments, SMA foils 810 and 820 are heated by direct contact conduction, e.g., contacting SMA foils 810 and 820 with a heated material, such as a resistance heated metal or the like. In one embodiment, SMA foils 810 and 820 are heated by convection, e.g., exposing SMA foils 810 and 820 to a heated airflow or the like.

In another embodiment, impedance discontinuity elements 162 and 164 are SMA coil springs 900 disposed between a window 1 10 and frame 130, as shown in Figure 9. Applying a control current, in one embodiment, to SMA coil springs 900, e.g., for heating SMA coil springs 900, increases the spring constant by about a factor of ten. In other embodiments, SMA coil springs 900 are heated by direct contact conduction, e.g., contacting SMA coil springs 900 with a heated material, such as a resistance heated metal or the like. In one embodiment, SMA coil springs 900 are heated by convection, e.g., exposing SMA coil springs 900 to a heated airflow or the like.

In various embodiments, impedance discontinuity elements 162 can include piezoelectric actuators, and impedance discontinuity elements 164 can include SMA actuators and vice versa. In some embodiments, impedance discontinuity elements 162 can include passive impedance discontinuity elements, and impedance discontinuity elements 164 can include active impedance discontinuity elements, such as piezoelectric and/or SMA actuators, and vice versa. For example, in one embodiment, impedance discontinuity elements 162 are SMA coil springs and impedance discontinuity elements 164 are passive coil springs. When no current is supplied to the SMA coil springs, the passive and SMA coil springs have the same stiffness. On the other hand, when current is supplied to the SMA coil springs, the stiffness of the SMA springs is increased, e.g., by up to a factor of ten, and the passive and SMA coil springs have a different stiffness. Figure 10 illustrates a control apparatus 1000 for controlling sound radiation from a window according to another embodiment of the present invention. In this embodiment, impedance discontinuity elements 162 and/or 164 are actuators, e.g., piezoelectric and/or SMA actuators. An output of controller 1010 is coupled to each of impedance discontinuity elements 162 and/or 164. An input of controller 1010 is coupled to a vibration sensor 1020, e.g., a piezoelectric sensor, such as piezoelectric sensor 710 of Figures 7A and 7B, etc. In one embodiment, vibration sensor 1020 is attached to a windowpane 1 10 adjacent periphery 140, as shown in Figure 10. In another embodiment, vibration sensor 1020 is disposed between a windowpane 110 and frame 130, as further shown in Figure 10. For some embodiments, impedance discontinuity elements 162 and or 164 are as described for Figures 7 A or 7B and include a sensor and an actuator.

Controller 1010 receives signals (for example sensed voltage V_se,_ae) from vibration sensor 1020 indicative of vibrations adjacent periphery 140 of the windowpane 1 10 transmitted to vibration sensor 1020. Controller 1010 generates and transmits signals to impedance discontinuity elements 162 and/or 164, e.g., a control voltage Vc for a piezoelectric actuator or a control current Ic for a SMA actuator, to adjust the impedance between the windowpane 1 10 and frame 130.

In various embodiments, the impedance is adjusted to create an impedance discontinuity adjacent periphery 140 of a single windowpane 1 10 that is vibrating due to sound waves impinging thereon. The stiffness discontinuity acts to modify the vibration energy distribution within the windowpane 1 10. For various embodiments, the stiffness discontinuity acts to reduce the vibration energy of the windowpane 110 and thus the sound radiation therefrom. In another embodiment, impedance discontinuities adjacent periphery 140 of the windowpane 1 10 redirect or confine vibration energy to a predetermined part of the windowpane 1 10 or frame 130. In some embodiments, a passive impedance discontinuity element is used to dissipate the redirected or confined vibration energy.

Figures 1 1 A and 1 IB respectively illustrate vibration energy distributions within a conventional windowpane and a windowpane having impedance discontinuities adjacent a periphery of the windowpane according to an embodiment of the present invention, as obtained from a finite-element computer simulation. It is seen that the impedance discontinuities act to modify the vibration energy distribution within the windowpane. Moreover, for this embodiment, it is seen that modifying the vibration energy distribution acts to reduce the vibration energy, e.g., by about three orders of magnitude.

In other embodiments, adjusting the impedance creates an impedance discontinuity between the peripheries of successive windowpanes, such as between windowpanes 1 10) and 1 10₂, as well as impedance discontinuities adjacent the periphery of each of the windowpanes. For example, for windowpanes 1 10ι and 1 10₂, when sound waves impinge upon windowpane 1 10], an impedance discontinuity adjacent periphery 140 of windowpane 1 10] acts to modify the vibration energy distribution within windowpane 1 10]. For various embodiments, the impedance discontinuity adjacent periphery 140 of windowpane 1 10] acts to reduce the vibration energy of windowpane 1 10]. Moreover, an impedance discontinuity between the windowpanes 1 10] and 1 10₂ acts to reduce the transfer of vibration energy from windowpane 1 10] to windowpane 1 10₂. An impedance discontinuity adjacent periphery 140 of windowpane 1 10₂ acts to modify the vibration energy distribution within windowpane 1 10₂. For various embodiments, the impedance discontinuity adjacent periphery 140 of windowpane 1 10₂ acts to reduce the vibration energy of windowpane 1 10₂ and thus the sound radiation therefrom. In another embodiment, impedance discontinuities adjacent periphery 140 of each of windowpanes 1 10] and 110 redirect or confine vibration energy to a predetermined part of each the windowpanes 1 10] and 110₂ or frame 130. In some embodiments, passive impedance discontinuity elements are used to dissipate the confined or redirected vibration energies. Figure 12 is a flowchart of a method 1200 for controlling sound radiation from a window according to another embodiment of the present invention. At block 1210, vibration sensor 1020 senses vibrations adjacent periphery 140 of a windowpane 1 10 of window 100 that is vibrating due to sound waves impinging thereon. A signal indicative of the vibration is transmitted from vibration sensor 1020 to controller 1010. Controller 1010 determines a vibration energy distribution within the windowpane 1 10 and thus the sound radiation from window 100 at block 1220. In one embodiment, controller 1010 calculates the vibration energy distribution in the windowpane 1 10 and thus the sound radiation from window 100 from the vibrations at periphery 140 as indicated by signals from vibration sensor 1020. In another embodiment, controller 1010 compares signals from vibration sensor 1020 to historical vibration data (usually called "baseline data" by those skilled in the art) to determine the vibration energy distributions in the windowpane 1 10 and thus the sound radiation from window 100.

When the vibration energy is above a predetermined level at decision block 1230, controller 1010 determines, e.g., from calculations or comparisons to baseline data, the stiffness distribution at periphery 140 for reducing vibration energy below the predetermined level, for modifying the vibration energy distribution within the windowpane 1 10, or for redirecting or confining the vibration energy to a predetermined part of the windowpane 1 10. Subsequently, at block 1250, controller 1010 transmits signals to impedance discontinuity elements 162 and/or 164 to adjust the impedance between the windowpane 1 10 and frame 130 for obtaining the above-determined stiffness distribution adjacent periphery 140. Method 1200 then returns to block 1210. When the vibration energy is less than or equal to a predetermined value at decision block 1230, method 1200 ends at block 1260.

In one embodiment, impedance discontinuity elements 162 and/or 164 induce a set of forces proportional to the spatial derivative (i.e., strain, shear force) of the structure at the point of application. In another embodiment, impedance discontinuity elements 162 and/or 164 induce a set of forces defined by a vortex power flow (VPF), e.g., as described in U.S. Patent Application Serial No. 09/724,369, entitled SMART SKIN STRUCTURES, filed November 28, 2000 (pending), which application is incorporated herein by reference.

Conclusion

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments shown. Many adaptations of the invention will be apparent to those of ordinary skill in the art. Accordingly, this application is intended to cover any adaptations or variations of the invention. It is manifestly intended that this invention be limited only by the following claims and equivalents thereof.