TW462201B - Acoustic device - Google Patents

Abstract

From one aspect the invention is an acoustic device, e.g. a loudspeaker, comprising a resonant multi-mode acoustic radiator panel having opposed faces, a vibration exciter arranged to apply bending wave vibration to the resonant panel to produce an acoustic output, means defining a cavity enclosing at least a portion of one panel face and arranged to contain acoustic radiation from the said portion of the panel face, wherein the cavity is such as to modify the modal behaviour of the panel. From another aspect the invention is a method of modifying the modal behaviour of a resonant panel acoustic device, comprising bringing the resonant panel into close proximity with a boundary surface to define a resonant cavity therebetween.

Description

4 6 2 20 1 V. Description of the Invention (1) Technical Field The present invention relates to a sound device, and more particularly, but not exclusively, to a speaker incorporating a resonant multi-mode resonance wall acoustic radiator, for example, our international The type described in Patent Application No. W 0 9 7/0 9 8 4 2 is also. The speaker described in W097 / 0 9 842 has become known as a distributed mode (DM) speaker. Generally speaking, they all use a distributed mode loudspeaker (DML) combined with a thin, lightweight and flat resonant wall. These surface walls radiate the sound energy from each side in an equal amount in a complex diffusion manner. Although this is a useful feature of distributed mode loudspeakers, it has a variety of real-world conditions in which, due to this application and its boundary requirements, a unipolar form of distributed mode loudspeaker is preferred. In these applications, such advantageous products may be lightweight and thin and not easily noticeable. BACKGROUND From the international patent application No. W 0 7 7/0 9 8 4 2 it is known that a multi-mode resonant acoustic radiator is installed in a relatively shallow sealed box, so that the radiator from the radiator is enclosed. Acoustic radiation from one surface. It should be noted in this regard that the term "shallow M-" in this article refers to a typical ratio of a piston cone speaker drive unit in an effective volume enclosed body. A typical volume to piston diaphragm area ratio may be 80: 1 expressed in milliliters (m1) versus square centimeters (cm2). A shallow enclosure for a resonant wall speaker may have a ratio of 20: 1, where there is a piston-type drive that lumps the air volume But rarely related.

4 6 2 20 1 V. Description of the invention (2) Description of the invention According to the present invention, an acoustic device is composed of a resonant multi-mode acoustic resonator or radiator wall having an opposite surface and a device defining a cavity, the cavity being closed in one place At least a portion of the wall surface is configured to block acoustic radiation from the wall surface portion, wherein the cavity is in such a manner as to modify the mode behavior of the radiator body wall. The cavity is sealed. A vibration exciter may be configured so that a curved wave vibration is applied to the resonance wall to generate an acoustic output, so that the device functions as a speaker. The cavity size can be such that the mode behavior of the resonant wall is modified. This cavity may be shallow. It may be shallow enough so that the distance between the cavity surface adjacent to this wall surface and its wall surface is sufficiently small, thus creating a fluid coupling with this resonant wall. The resonance mode in the cavity can be composed of an orthogonal mode parallel to the resonance wall (that is, a mode modulated along the resonance wall) and a vertical mode perpendicular to the resonance wall. In terms of favorite methods, the cavities are sufficiently shallow. Therefore, the orthogonal mode (X, Y) is more prominent than the vertical mode (Z) when modifying the mode of the resonance wall. In each specific example, the frequency of the vertical mode can be outside the important frequency range. The ratio of the volume of the cavity to the resonance wall (m 1: cm 2) may be less than 10: 1, for example, in a range of approximately 10: 1 to 0.2: 1. The resonant wall can be terminated at its edges by a generally elastic perimeter. This perimeter may resemble the rolling perimeter of a conventional piston drive unit and may consist of one or more corrugations. Such an elastic periphery may be composed of a foamed rubber strip.

Page 6 462201 V. Description of the invention (3) Regarding the conversion method, 'the edge of this staggered wall can be sandwiched in a closed body, for example, with our common standby pcT patent right proposed on April 9, 1999 The same is stated in the case PCT / GB9 9/0 04 04. Such a closed body can be regarded as a shallow plate, which contains a fluid, and the surface of the fluid can be regarded as having a wave-like functional performance, and the specific characteristics depend on the fluid (air) and its volume or The geometry of the tank is determined by ^. This resonant wall is placed in coupling contact with this wave surface and excited by a surface wave of the spectral wall to excite the fluid. Conversely, the natural wave characteristics of the fluid interact with the staggered wall, and thus ‘correct its functional behavior. This is a duplex coupling system with novel acoustic characteristics in the field of the present invention. According to another characteristic statement, the present invention is related to the modification of the resonance wall acoustic device. The 5th aspect of the invention includes the promotion of the resonance wall and a boundary 丄: becoming tight 郴 to limit the vibration cavities between them. . Brief description of the formula "1" Figure 1 is a cross-sectional curve diagram of the first specific example of the sealed box resonance wall speaker Figure 2 is a cross-section of a specific example of the figure of an enlarged scale i Figure 3 is a sealed box A cross-sectional view of a second specific example of the resonant wall. Figure 4 shows the self-ejecting decorative mold speaker on both sides. Figure 5 shows the sound pressure level (solid line) in free space and the distance 35 cm from the wall. Comparison between distributed mode speakers (DML) (dotted line). Figure 6 shows the comparison of the reflective surface around the wall between the front and back of the distributed mode speaker in a free space.

$ 7 • Page 4 6 2 20 1 V. Description of the invention (4) Figure 7 shows a loudspeaker according to the invention = Figure 8 shows a distributed mode loudspeaker resonance wall system. FIG. 9 illustrates the coupling of the components. FIG. 10 illustrates a single-wall characteristic function. FIG. 11 shows the frequency response scale of the first 10 vacuum internal resonance wall modes. Fig. 12 shows the frequency response scale of the same mode in a speaker according to a specific example of the present invention. Figure 13 shows the effect of the closure on the wall velocity spectrum. Figure 14 illustrates two pattern shapes. Figure 15 shows the frequency response of the reactance. Figure 16 illustrates wall speed measurement. Figure 17 illustrates a microphone farm for measurement. Figure 18 shows the mechanical impedance of different wall sections. Figure 19 shows the power response of different wall sections. Figure 20 shows the polar response of different wall sections. Figure 21 shows a microphonic device for measuring the internal pressure of a closure. Figure 22 shows the internal pressure profile. Figure 23 shows the internal pressure measured using the array of Figure 21. Fig. 24 shows the speed and displacement of different wall portions. Figure 2 5 shows the velocity spectrum of the A 5 wall in free space and in the enclosure. Figure 26 shows the velocity spectrum of another A5 wall in free space and in the enclosure. Figure 27 shows the power response of the A 2 wall in a double-depth enclosure. Figure 28 illustrates equalization using a filter.

No. 8 it »Πη ni _ Case No. 88105770 (/? Amendment __ V. Description of the invention (5) In these drawings and more particularly with reference to Figures 1 and 2, the sealed box speaker 1 consists of W 0 9 7/0 9 8 4 One of the types described in the application No. 2 is a box-shaped closure 2 in which the resonant acoustic radiator 5 is closed at its front end. The radiator 5 is energized by a vibration exciter 4 It is sealed to an enclosure around its periphery by an elastic suspension 6. The suspension 6 is composed of, for example, opposed elastic strips 7 of foamed rubber placed in frame members 9, 10 of individual humanoid parts, and these frames The components are held together by the fasteners 11 to form the frame 8. The inner surface 14 of the wall 3 behind the closure 2 is made of hardened ribs 12 to minimize the vibration of the rear wall. Such closures It can be a plastic molded product or a casting with this hardened rib. The resonant wall in this specific example can be A 2 size and the depth of the cavity 13 can be 90 cm. The specific example of the speaker in Figure 3 is general In terms of the same as the specific examples of Figs. 1 and 2, but here the radiator wall 5 is installed in the Between the edge of the projectile 5 and the sealing of the cavity, for example, a single elastic strip is suspended from a foam rubber 6. The size of the radiator wall can be A5 and its degree can be about 3 or 4 cm. It is known that although the specific examples of Figs. 1 to 3 are about speakers, it can also use the general type of devices of Figs. 1 to 3 to produce an acoustic resonance wall to modify the sound of a space (such as a reception room or auditorium). Performance, but the description of the vibration exciter 4 is omitted here. As shown in the figure, when compared with the piston speaker, the resonance wall of this configuration can provide an item with a very small closed volume based on the size of the diaphragm. Very useful frequency bandwidth. The Zitter test is responsible for the role of such bounds and distributed modes.

O: \ 57 \ 57900.ptc Page 9 2001.07. 05.009 462201 V. Description of the invention (6) The mechanism with the least interaction and further shown in the figure, that is to say, in short, a simple passive network waiting for others may generate a All you need for a flat power response curve. It has also been proven that, in this representation, a: distributed mode loudspeaker can generate a nearly ideal hemispherical directional pattern into a 2.7 space in its operating frequency range. A closed-form solution is proposed. This method is the result of solving the curve-wave equation for such a hybrid system with a combination of vibration walls and closures. : Obtain the acoustic impedance function of this system and use it in order to calculate the effect of this coupling closure on the characteristic frequency, and predict the relevant transition and increase of the screen mode. Investigate experimental measurements of several samples that change lumped parameters and sizes; compare these measurements with results from analysis mode. Figure 4 illustrates the typical polar response of a free-distribution mode speaker. Note that the reduction in pressure in the plane of the resonant wall is due to the offsetting effect of acoustic radiation at or near its edges. When a distributed mode loudspeaker is approached to a boundary that is particularly parallel to the surface of boundary i, the distance from which the surface is phased out, is reduced to low by about 500 square centimeters of surface area. | At about 15 cm, acoustic interference began to occur. Its effect varies according to its severity 1 degree and the nature of the distance from the boundary and the size of the wall. In any case, the result is a constant reduction of low-frequency extension, a sharpened response curve in the bottom middle range, and some aberrations in the middle range and bottom frequency triples, as shown in the example in Figure 5. Representation is the same in. Because of this peak, regardless of the fact that it is easy to compensate for the spikes, the application of a "free" distributed mode speaker close to a boundary becomes very limited.

Page 10 4 6 2 20 I. 5. Description of the invention (7) '丨 The wall will only be blocked when a distributed mode speaker is placed in a closed box or so-called i π infinite reflection surface with a large volume. Radiation from the rear and generally increase the radiation in the front in the middle and low-frequency response curve, these benefits come from two characteristics. The first is due to the lack of interference, and so on; The effect is caused by the front and rear radiation at the frequency of the acoustic wavelength of the air t which can come from the wall space; the second comes from the enhancement of the reflection surface and the radiation I from the middle to the low frequency boundary in the 2ττ space For the sake of illustration, see Figure 6. 丨 Here, we can see that using a harmonic surface with a surface area of 0,25 square centimeters, the vibration wall will reach about 20 dB at 100 Hz. Although this is the frequency A positive benefit when bandwidth is at its maximum, but [it may not actually be added unless the application itself is useful for the solution. Suitable applications include flat-top speakers and custom built-in walls. F! In various other applications, This " infinite reflection surface 11 structure can be shaped! It can have the luxury of luxury with a closed volume of air behind the resonance wall. These applications can also benefit from the thinness and lightness of the speaker. | The goal is to gain an understanding of this form of configuration and provide analytical solutions. A lot of work has been done to support traditional piston speakers in various modes of operation, especially in predicting low-frequency behavior when used in a closed body. It is worth mentioning that distributed mode speakers are very recent developments, so there is little prior knowledge of these issues in order to help obtain solutions for similar analysis. In the description that follows, A method is adopted, which is a small closure to the load

Page U 462201 丨 V. Description of the invention (8) The distributed mode speakers provided in the case of various mechanical and acoustic interfaces provide a set of useful solutions. ! The system under this analysis is shown diagrammatically in Figure 7. In this example, the front side of the resonant arm is radiated in free space, while the other side is equipped with a closed body. This coupling system can be viewed as a speed and pressure network as in the case shown in Figure 8. All components are I'I from left to right; motor drive part, mode system of resonance wall, and sound system. ! The velocity of a curved wave electromagnetic field above a vibrating wall is responsible for its acoustic radiation. Such radiation sequentially causes a reactive force that corrects the vibration of the resonance wall. In the case of a distributed-mode loudspeaker that radiates equally from both sides of i, it is the I radiation impedance of the reactive element, which is usually not significant when compared with the mechanical impedance of the resonance wall. However, when this resonance wall radiates in two small enclosed bodies, the effect of acoustic impedance due to the radiation behind it will no longer be small, and in fact, it will modify and increase the proportion of the j-reading wall shape. .

I According to the representation in Figure 9, this coupling is equivalent to a mechanical acoustic closed-loop i | road system, in which the reactive sound pressure is caused by the velocity of the resonance wall itself. This pressure will modify the mode distribution of the variable curve electromagnetic field, which in turn has an effect on the sound pressure response and the directionality of the resonant wall.丨 In order to calculate the directivity and check the internal force and flow path of such a system, the problem of the screen speed must be solved. Then, this far-field sound pressure response can be obtained by using the Fourier transform at this rate, which is the same as that described in PANZER, J; HARRIS, N; , The dissertation was in the 105th edition of San Francisco in 1988

Page 12 4 6 2 201 V. Description of Invention (9) The number proposed in the AES meeting is 4783. Therefore, it is possible to obtain such forces and flow paths through network analysis. ≫ The approach to this problem is based on CREMER, L; HECKL, M; UNGAR, E; ^ SPRINGER " 1973 Structure-born sounds and BLEVINS, RD,

In 1984, KRIEGER. Publ., MALABAR " Natural frequency and mode shape A formula 11 and other vacuum internal resonance wall characteristic functions (3, 4), etc., were derived from the speed and pressure of all systems. For example, the velocity at any point on the wall can be opened from equation (1) st. c〇 / ⑽) = Σ Ypiij ^) 'F〇i (it〇) * ^ pi (x〇.y〇)' ^ pi (xy) (1) When coupled to the motor lumped element network and its immediate In the case of acoustic boundary, this series represents a solution to the differential equations that explain the screen polar wave. Equation (2)

Page 13 4 62 20 1 V. Description of the Invention (ίο) Features. The orthogonality of 0 p; is a necessary condition for a proper solution to the differential equation (2). The set of characteristic functions and their parameters are obtained from the homogeneous form of equation (2), that is, after turning off these driving forces. In this case, the resonant wall can only vibrate at its natural frequency or the so-called characteristic frequency (;); in order to satisfy the boundary conditions. .. In equation (2), 0pi (x, y) is still the value of the i-th screen characteristic function at the position where such a rate is observed. 0pi (XQ.yc)) is the characteristic function at the position where I adds the driving force Fpi (jt0) to the resonance wall. This item: The driving force includes the transfer function of the electromechanical group of the drive speed controller at (X., y.), For example, such as an exciter, suspension, etc. Thanks to this

I: The driving force depends on the resonance wall speed at the driving point, so similar feedback conditions such as about: mechanical acoustic coupling are at the driving point, although this effect is actually very small.

I Figure 10 provides an example of the magnitude distribution of a single characteristic function above the wall of a distributed mode speaker. These black lines are nodal lines at which the velocity is zero. As the mode index is increased, the rate pattern becomes more complicated. As for the medium-sized resonance mural, it is bound to add up to about 200 modes in order to cover the audio range. The mode admittance [YpKj ω] is a trade-off function of these modes and is determined by which amplitude and at which phase, the i-th mode is added to the sum of! Equation (1). According to the equation (3), Ypi depends on the driving frequency, the characteristics of the screen, and, most importantly, in this document, depending on the acoustic impedance of the enclosure and the impedance due to free electromagnetic field radiation.

Page 14 462201 V. Description of the invention (11) Y,

Sn * dr pi (s)? Pi Sp + Sp-dpi + γ ^ ι (3) 31) = 3 /% is a 1 ^? 13〇6 frequency variable normalized to the fundamental resonance wall frequency (0 ()) (Ωρ), this variable depends on the bending stiffness of the resonance wall! ^ And the mass Mp, that is ωρ2 = κρ / Μρ. Rpi is the mode resistance due to material loss and is the resonance at Sp = λρί to explain the value of Ypi (jw). Api is a function of a certain ratio and is the function of the i-th screen pole characteristic value λ pi and the total radiation impedance Zmai, as described in equation (4).

Tpi (s) =. Λρί + sp-Zmai (j〇 >), p · iVlp In a vacuum situation (2mai = 0), the second term in equation (3) becomes quadratic with the reduction factor dpi Passband transfer function. Figure 11 shows the frequency response scale of Ypi (jft0) in the vacuum of the first 10 modes of one resonance wall when clamped at the edge. The characteristic frequencies of the resonance wall all coincide with the peaks of these curves. If now Mounting the same resonant wall on a closed body not only shifts these modes by frequency, but also corrects them as seen in Figure 12. This occurs because the two modes of the system between the resonant wall and the closed body occur. As a result of the interaction, the model admittance of the whole system is no longer a quadratic function like in the vacuum case. In fact, a higher-order polynomial can be used to expand the denominator of equation (3), which will show its composition. Enlarged characteristic function. The frequency response chart in Figure 13 shows the effect of the closed body on the resonance wall velocity spectrum. Two frequency response curves are calculated under the same driving conditions.

mm

Page 15 4 6 2 2 0 1 V. Explanation of the invention (12) However, the left curve shows the case in a vacuum, and the right curve shows the rate when a closed body is loaded on both sides of the resonance wall. A pair of closures was used in this example to exclude the radiation impedance of air. The observation point is at the driving point of the exciter. What is clearly visible is the effect of this resonance wall frequency shift on the higher frequencies that are also seen in the right graph in Figure 12. It is worth mentioning that a more uniform distribution curve describing the rate spectrum will be obtained due to the effects of the closed volume, and the subsequent increase in the number and density of modes. Its mechanical radiation impedance is the ratio of the reactive force due to radiation to the velocity of the resonant wall. For a single mode, this radiation impedance (considered as a constant above the area of the resonance wall and can be expressed in terms of the acoustic radiation power Pai of a single mode. In this way, the i-th mode can be described by equation (5) Mode radiation impedance. Z 2

Zma i-2 Jr < V] > (5) < Vi > is the average velocity above the resonance wall of the i-th mode. Since this value is squared, it is always a positive value and a real number. Therefore, the characteristics of the radiation impedance zmai are directly related to the characteristics of the acoustic power. Such impedances are generally complex values. The real value of Pai is equal to the radiated far-field power. This power contributes to the resistive part of zmai, which results in a reduction of the rate field of the resonant wall. Pai's imaginary part is caused by the energy storage mechanism of the coupling system in order to concede the positive or negative reactance of z „ai. A positive reactance is caused by the appearance of sound quality. For example,

Page 16 This electromechanical spring 462201 V. Description of invention (13) is an example of radiation in free space. On the other hand, the z-resistance indicates the existence of a sealed enclosure with the same amount of hardness. The name 'item " quality " radiation resistance is caused by no compression' and when compressed air does not transfer it When there is n-type impedance. The main effect of the imaginary part of the radiation impedance is the transfer of the true frequency of the resonance wall. A positive Zmai reactance (mass) will cause the chip frequency to shift down ', while a negative reactance (hardness) will reduce the characteristic frequency to the gray frequency and suppress the pane mode itself | an effect will $掂 ± ^ 7 The main drought grips the main control 杻. This phenomenon is shown in the graphs in Fig. 1 and 4. V:] solution shows that the symmetrical pattern shape will cause the pressure of the air, and the symmetrical pattern shape of i Π: ϊ makes the air not at any level. Quality " Behavioral performance. When the interaction of their body reactance = the new modes appearing in the system are all caused by resonance reaction. Figure 15 shows such a spherical line. The left diagram shows the imaginary part of the radiated impedance of the limb. The frequency of the spring-type 1'electricity 2 ==== symmetrical window glass mode is typically a negative i1 direction, the characteristic frequency of the first closed body, the characteristic frequency within this range. The parallel shift is at this frequency. When the ratio of fine t is typical of the resonance glass mode within the region, the right chart shows a "mass-type secondary reactance behavior part if the closed body is dense, and here I ', and it is parallel to the surface of the window glass The emission impedance is an example of the equation (H). Then, the negative value of the polar mode of the i-th screen. According to the air transport of the item, the "characteristic characteristics of the air inside the bomb moves up." 1 Command the solution to be condensed, that is, when the left and right turns are separated, the wall and the closing rate response curve generate a vacuum of large reactance #symmetric window 0. The rigid wall of the mechanical 462201 V. Description of the invention (14) Zjnai = 1.ω · Ρ3 Σ (6) W (ik, u is the coupling integral that considers the boundary conditions of the cross section and involves the characteristics of the screen and the closed body. The index i in equation (6) is the number of screen modes; Lri is the closed body. Depth; and kz is the component of the number of mode waves in the z direction (perpendicular to the window glass). For a rigid rectangular closed body, kz is described by equation (7): kz {kl) =

The indices k and 1 are the number of closed ceremonial orthogonal modules in the X and y directions, where Ldx I and Ldy are the dimensions of the closed body in this plane. Ao is the area of the window glass and Ad is the cross-sectional area of the closed body in the X and y planes. Equation (6) is a complex function that specifies the interaction between the window pane and the closed phantom. In order to understand the nature of this formula, let's simplify it. The method is to limit this system to only the first mode of the window glass and the Z mode of the closed body (k = 120). This move will A simplified relationship will be generated. ^ maO = -j 'Cot {kz · Ldz) 丨 Ad, (⑻ Equation (8) is a familiar driving point-impedance of a closed tube, [ie equation 46-201 V. invention description (15) can be further simplified Such as I formula (6)]. If its product K: j under 0

Z

maO A; 1 (9) where c ab / (p:) is the acoustic compliance of a closed body with volume vh. Equation (9) is the low-frequency lumped component mode of the enclosure. If the source is a rigid piston with mass Mms and the suspension has compliance Cms, then the basic "mode" of the coupling system with characteristic value λ pc > = 1 and equation (4) will become the basis. The familiar relationship represented by the equations (1 0) and (1), and has the equivalent mechanical compliance of the enclosed air volume Cmb = Cab / A () 2. Ϊρο 1 +

Cr (10) has completed various tests to determine the effect of the tuner. In addition to the closed performance, and have designed various measurements of the performance of a distributed mode speaker resonance wall, the establishment of such models have chosen different sizes and large walls as our test targets. It should be sufficient for different sizes and other differences in order to investigate the behavior of the DNM resonance wall in a shallow back enclosure versus a distributed mold lifter in proportion to prove the theoretical model and the effect of pre-existing enclosures. The limits of the behavior of a coupled-mode system for accuracy. Two distributed-mode loudspeaker resonances with different characteristics It has been decided that these projects, on the one hand, have a good range in most of their characteristics. The first group

Page 19 4 6 2 2 0 1 V. Description of the invention (16) " A " The small A5 size vibrating walls with U9 centimeters and χ2120 centimeters with three different most mechanical characteristics are selected. A5_1 polycarbonate S film on polycarbonate honeycomb; A5-2 carbon fiber on Rohacel 1; and A5-3 Rohacell with skin. The '' B " group was once chosen to be a larger 8 pieces, approximately A2 size of about 42 cm x 592 cm. In addition, A 2-1 was made of glass fiber membranes on polycarbonate honeycomb cores, while A2-2 was a carbon fiber membrane on aluminum honeycombs. Table i lists most of these characteristics. 1 The speed control function is performed by the exciter at the best case point. Two types of exciters have been used. Here, it has been most suitable for testing the size of the vibrating wall. In the case of vibration walls, Bl = 2. 3 ding m and Re = 3. 7 were used in the case of B1 = 1.0 Tm, Re = 7. 3 Ω and Le = 36 in the case of η 6 " ^ -U type pure type. small

Zm size _ (Ns / m) (mm)-24.3 5X592X420 ^ 60.0 7.2X592X420 _ 7.5 2X210X 149 _1 1 · 8 2X210X149 2.7 3X210X149 The resonance wall used for suspension and sound sealing was installed on the adjustable depth 28, 40 The closures were manufactured in mm depth and manufactured at 20, 50, 95. 1 Measurements were made on the back closures with a non-wood soft polyhelium ethyl acetate foam for each test case. It has been adjusted from 130 to 130 mm with 5 and 3 sets of stray walls of the "A11" resonance wall. Various @ #closed body depth to complete and

Resonant wall type B (Nm) Α2-1 PC with glass 10.4 Α2-2 A1 with carbon 57.6 Α5 ^ 1 PC with PC 1.39 Α5-2 ___. Rohacell with 3.33 Α5-3 Rohacell core 0.33 No. 20 pages 4 6 2 20 1 V. Description of the invention (17) The results were documented. The laser vibrometer was used to measure the velocity and displacement of the staggered wall. The linear frequency scale of 160 points is used to cover the important frequency range. The device shown in Figure 16 was used to measure the mechanical impedance of the staggered wall by calculating the ratio of the applied force at the driving point to the velocity of the resonant wall. TZ. According to this procedure, the lumped parameter information of the self-exciter calculates the same force applied. Although its own resonant wall rate feedback is within the motor circuit ', the direct loss is very weak. What can be expressed in the formula is to excite the small value of gB1 (1 to 3 Tm), assuming that the output impedance of the amplifier A is small (constant voltage, the mode transition fed back to this electrical system will be sufficiently weak: difficult Makes this assumption exciting. Therefore, I will ignore this approximation = small error. Figure 18ay shows the wrong vibration wall: mechanical impedance ... The data of the member are all measured and applied by the free laser vibrometer. The measured value of the acting force. Note that the minimum impedance value of each closed body depth occurs at the resonance mode of the system. Sound pressure levels and polar responses of the J-type resonance walls; Sentence: in a large space of 3 500 cubic meters Measured in the inside and gated by HLS 2 to 1 4 MS using MLSSA depending on the measurement. According to the representation in Figure 丨 7d and Figure = The device shown is completed using a 9-microphone array system Power measurement. These measurements are plotted in Figures 19a to f for various closed-body depths. The system's vibration is highlighted by the marks on the chart.

Page 21 462201 V. Description of the invention (18) The polarized responses of the A5-1 and A5-2 resonant walls are measured on a 28 cm deep closed body and the results are shown in the figure and 20b. When compared with the polar response of the free-mode speaker in Figure 1, they demonstrate the significance of the closed-back distributed-mode speaker in terms of its improved directivity. Β To further investigate the effect of the closed body on the behavior of the resonant arm, in particular When the combined system resonated, a special coupling was completed to allow the internal pressure inside the enclosure to be measured at nine predetermined points, as shown in Figure 21. Insert the microphone into the opening inside the back panel coupled to an A5 enclosure at a predetermined depth, while tightly blocking the holes in the other 8 positions with a hard rubber grommet. The microphone is mechanically isolated from the enclosure by a suitable rubber grommet. From this kind of data, a round temple pattern 'has been generated to indicate the pressure distribution when the system t is vibrating and on either side of this frequency, as is the case shown in Figs. 22a to c. Pressure-frequency response curves are also plotted for the nine positions shown in FIG. This kind of graph shows the good definition of the resonance region for all the curves about the measurement points in the closed body. However, its pressure tends to change in the cross-sectional area of the closed body with increasing frequency. Measure the vertical components of the velocity and displacement above these resonance walls with a scanning laser vibrometer and plot the velocity and displacement distribution curves above these resonance walls to investigate the behavior of the resonance walls around the resonance walls of this coupling system. The results are documented. Several cases are shown in Figures 24a to d. These results are based on all the suggestions of moving the resonant wall. The performance of the fixed drum mode of the spectral wall at resonance is suggested, although when we move to the edge of the staggered wall, we use a smaller rate and displacement °.

4 6 2 20 1

V. Description of the invention (19) In fact, 'this behavior is based on all the conditions of the resonance wall', although the shape of the mode will change from case to case, but it depends on complex parameters including the hardness and quality of the resonance wall. , Size and boundary conditions 萁. And, τ. According to its limits and on an infinitely rigid resonant wall, the vibration of such a system will only be seen when the basic rigid body mode of the piston acts on the rigidity of the air volume of the resonant wall. It has been found that it is convenient to call this distributed mode speaker system resonance, "full body mode" or WBM. The entire theory of this coupling system has been implemented by a new converter company in a set of software. This A type of project has been used to simulate the mechanical and acoustic behavior of our test target in this article. This package does take into account all the electrical aspects of a resonant wall 'exciter and a mechanical or acoustical interface of a frame. , Mechanical and acoustic variables, and among other parameters, the far-field sound pressure, power, and directivity of the whole system are predicted. Figure 2 5a shows that it is clamped in a frame for equal amount of Korean shots from both sides— f is a logarithmic rate of free radiation of the A 5 -1 resonant wall in space. The 1 ° through line represents the analog curve and the dotted line is the measurement rate spectrum. At low frequencies, the far resonant wall enters resonance with the exciter. 1 〇〇 The disadvantage in the frequency range above 0 Hz is due to the lack of free-field radiation impedance in the analog mode. | Figure 2 5b shows the same resonance wall as in Figure 2 5 & Plant | There are two identical enclosures, each side of the museum's vibrating wall has _closes 丨 closes '', its cross section is the same as the resonant wall and has a depth of 24 cm. Design and use Body, in order to exclude the free-radiation magnetic field on one side of the resonance wall, and make the experiment independent of this free-field free-radiation impedance. It is important to note that this is the only type of experiment Room equipment

Page 23 462201 'V. Description of the Invention (20) ^ It is only used for theoretical verification. In order to promote such a resonance wall rate meter, the rear wall of two closed bodies was made of a transparent material to allow the laser beam to reach the surface of the resonance wall. Rohacell, which has skin but different most of its characteristics, has been used to repeat this kind of test with t all vibration walls A 5-3 and a certain result is shown in Figs. 26a and b. In both cases, simulations were performed using a logarithmic range of 200 points, while laser measurements used a linear range of 160 points. From the foregoing theory and work, it is clear that a small enclosure suitable for distributed mode speakers comes with a strange disadvantage among several benefits. This shows excessive power due to the WBM when the system is resonant as shown in Figures 27a and b. It is worth mentioning that in addition to this spike, among all other features, this closed distributed mode speaker can contribute a truly improved performance, including all increased power frequency bandwidth. What has been found is that in most cases, a simple quadratic stop-and-equalization network with an appropriate Q value can be designed. To equalize such a response spike, the Q value matches the Q value of the power response spike. In some cases, a single-pole high-pass filter often adjusts this situation by tilting the low-frequency region to provide a broad and flat power response. Due to the unique nature of the resonant wall of the distributed mode speaker and its resistive electrical impedance response, the design will remain very simple and simple, regardless of whether the filter is active or passive. Fig. 28a shows a position where a passive filter with a stop is added for equalization. Another example can also be seen in Figure 2 8b and c. The figure shows the unipolar EQ as one of the capacitors used in series with the speaker β. We have shown in this article that when the distributed mode speaker is used,

Page 24 462201 V. Description of the invention (21) When traveling on the wall, the minimum mutual number due to extreme characteristics must be used, so it cannot be projected. In extending this system, this may not be the case. The enclosed body shown in the figure will make it become! Acoustic performance is possible; a sharp contrast between a distributed mode speaker and a distributed mode speaker is generated by a simpler calculation! The mechanical sound characteristics of the closed sound body of the sound II I are observed with the appropriate tool I. It is observed that the system β is in depth and harmonic; both are very significant. However, at the time, the increase in low-frequency response: a rigid activity in a closed body, the complete counter-advantage of the complex double-difference function, and Kee ’s minimal system proves that. What the radiator did was that although a speaker and its system were present, this was predictable. In time-changing situations, beyond the degree, it is important to be careful to ensure that the latter is independent because of it. This kind of interaction is fixed at a distance from the boundary. The low-frequency response of the resonant wall has practical proposals that affirm many applications. Yes, the use of a distributed mode speaker has nothing to do with its immediate environment and makes such predictions. The developed mathematical model predicts and designs the degree of complexity in coupled systems with traditional pistons. From this work, it seems very clear (even by first-hand computer) that the characteristics of a distributed model are subject to complex interactions, which will make such systems become unregulated. It is also insignificant when comparing the size of the volume vibration wall that it will become marginal at a certain depth. Of course, the plugs are consistent. For example, a resonant wall with a closed body depth of 50 cm and a size of A2 can be designed to have a frequency bandwidth extending down to about 120 Hz, as shown in Figure 24. Another feature of a distributed-mode speaker with a small enclosed body is a significant improvement in the middle and high frequency response of such a system. Such feeling

Page 25 4 6 2 20 1: V. Description of the invention (22); the situation has appeared in many of the measurement and simulation curves in this article, of course, it is also expected by this theory! Obviously, the modest increase of such a resonant wall system is that I is responsible for most of this improvement, but the loss of the closed body can also affect this situation by increasing the overall reduction of this system. When the radiation behind this resonant wall is regarded as a natural ending, then the directionality of this closed system will change from a bipolar shape to a nearly heart-shaped behavior shown in Figure 17 situation. It is expected that the directivity of a distributed-mode loudspeaker with a closed back may find use in some applications, where strong lateral coverage is desirable. ! Power Response Measurements Only Found When Working with a Closed Distributed Mode System

I! Is most useful in order to observe areas of excessive energy that may require compensation. This is consistent with other work done on distributed mode speakers, where it was found

I | is that its power response is just the most representative acoustic measurement of the subjective nature of distributed mode speakers. When using this kind of power response, it has been found that what is implemented is a simple passband or a single-pole high-pass filter: all that is necessary to equalize the power response in this region.丨 It is worth mentioning that the various tests performed here have shown a good degree of interrelationship in identifying the complete ontology model of the system and its incidental characteristics.

Page 26 462201 Case No. 1 88105770 (Description of Correction Element Symbols in July, July C, July 5. Explanation of the Invention (23) 1 Sealed Box Speaker 2 Box Closure 3 Rear Wall 4 Vibration Exciter 5 Resonant Acoustic Radiator 6 Elastic suspension 7 Opposite elastic strips 8 Frame 9 > 1 0 Frame member 11 Fastener 12 Hardened ribs 13 Cavity 14 Internal surface

O: \ 57 \ 57900.ptc Page 26a 2001.07. 05. 027

Claims (1)

4 6 2 Jj__ B8105770 q〇 洋 February 7th Amendment. ¾ Charge 'device, which consists of a resonant multi-mode acoustic wall with one of the opposite surfaces. This device defines at least a part of the surface of a resonant wall, and its configuration is to contain the The sound of the surface part of the resonance wall, in which the cavity is in such a way, is to modify the mode behavior table of the resonance wall. According to the application, shallow and thin, coupled with the fluid of the wall 5, according to the percentage of the application, whether or not the JE quasi-repair JE 〇 Ming mode t v6. ≫ -7. 3 of which 〇, 2: So 8 mention νΰ · 夂 其 t The device 9, which has a bomb, is generally in accordance with the application department, and the cavity is in the range of 1 and the volume of the cavity according to the application. According to the application, the acoustic device according to item 1 of the peripheral scope is to modify the behavior of the mode of the cavity. The acoustic device according to item 2 of the scope of interest, wherein the cavity is the acoustic device according to item 3 of the scope of interest, wherein the cavities all cause the back side of the cavity facing the surface of the resonance wall to merge. The audio device of the fourth item of the utility model, in which X and Y are orthogonal to the main mode part. The sound device of the range 1, 2, 3, 4 or 5 is sealed. For acoustic devices in the range 1, 2, 3, 4 or 5, the ratio of the area of the resonance wall (m 1: c m2) is in the range of 10: 1 to the range 1, 2, 3, 4 or 5 In the acoustic device, the enclosure is installed in the cavity and sealed to the cavity. The acoustic device according to item 8 of the scope of the patent application is defined in the enclosure, and the enclosure is rich. O: \ 57 \ 579QO.ptc Page 27 2001. 02.12. 028 4 6 2 20 t Case No. rib 105770% year 厶 month Z said amendment ~, patent application scope, 2 '3' 4 and its configuration is 10. The speaker includes the sound device as described in item i or 5 of the scope of patent application, and has a vibration exciter to apply bending wave vibration to the resonance wall to generate sound output. 1 1. A method of multiplying the mode behavior performance of vibrating wall acoustic devices. This method includes bringing a resonant wall into close contact with a boundary surface to define a resonant cavity between them. O: \ 57 \ 57900.ptc Page 28 2001.02.12. 029