JP5140795B2 - Active sound insulation device, active sound insulation panel, and active sound insulation method - Google Patents

Description

  The present invention provides an active sound insulation device that suppresses the transmitted sound of the panel by exciting a predetermined portion of the panel disposed between the sound source side and the sound receiving side according to the sound emitted from the sound source, The present invention relates to an active sound insulation panel used in the active sound insulation device. The present invention also relates to an active sound insulation method using the active sound insulation device and the active sound insulation panel.

  Conventionally, in order to suppress the transmitted sound of a panel, the panel is made of a material having a large specific gravity such as iron or lead to make it difficult to vibrate. However, if the panel is made of a heavy material in this way, it becomes difficult to reduce the weight of the building, vehicle or equipment incorporating the panel. In recent years, the panel has been transmitted without increasing the weight of the panel. The technology that suppresses the coming noise is gaining attention.

  Among them, as shown in FIG. 1, a panel for separating the sound source side and the sound receiving side, a sensor for detecting sound emitted from the sound source, and control for generating a control signal according to the sound detected by the sensor "Active sound insulation that suppresses the transmitted sound of the panel using the control means and an actuator that suppresses the transmitted sound of the panel by vibrating (vibrating) a predetermined portion of the panel based on the control signal generated by the control means Many studies on technology called "control" have been conducted.

  For example, Fuller has studied active sound insulation control that suppresses transmitted sound of a circular panel with a fixed periphery using one or two actuators, and active sound insulation control has a great effect on suppressing transmitted sound. It is shown by calculation (see Non-Patent Document 1). Saruwatari et al. Have studied active sound insulation control for suppressing vibration of the panel (see Non-Patent Documents 2 and 3) for the purpose of suppressing sound transmitted through the panel (flat plate).

  However, in these active sound insulation controls, the transmitted sound suppression effect changes in a complex manner depending on the number and arrangement of actuators. To obtain the desired suppression effect, the panel excitation is taken into account, for example, the type of sound source. It was necessary to determine the method by trial and error.

  Johnson et al., On the other hand, focused on the radiation mode that is the dominant factor of transmitted sound, sensed the volume velocity equivalent to the first-order radiation mode at a low frequency, and reduced the volume velocity to reduce the transmitted sound. Proposed active sound insulation control technology (see Non-Patent Document 4).

  This Non-Patent Document 4 describes that a phenomenon (called “control spillover”) in which the control effect by active sound insulation control cannot be obtained at a specific frequency appears. This control spillover can be prevented if a distributed constant type sensor using a piezoelectric film or a volume velocity sensor or volume velocity actuator constituted by an actuator can be realized. Henrioulle et al. Experimentally examined the method of Johnson et al. Using a piezoelectric film (see Non-Patent Document 5).

  However, since an actuator using a piezoelectric film has a weak force for vibrating the panel, active sound insulation control technology incorporating such an actuator is difficult to put into practical use at present.

  In addition to these, many active sound insulation devices and active sound insulation methods applying active sound insulation control technology have been proposed so far (see, for example, Patent Documents 1 to 7). Nothing was found that could provide excellent sound insulation performance for sound in the frequency band.

JP 05-289678 A Japanese Patent Laid-Open No. 06-149272 JP 07-056580 A Japanese Patent Application Laid-Open No. 07-210174 JP 08-314471 A Japanese Patent Laid-Open No. 10-254458 JP 2004-036299 A Fuller, C.R., Active control of sound transmission / radiation from elastic plates by vibration inputs: I. Analysis, Journal of Sound and Vibration, Vol. 136, No. 1 (1990), pp. 1-15. Katsuaki Saruwatari and Kazuto Sado, “Plate Vibration Control Method for Active Sound Insulation”, Transactions of the Japan Society of Mechanical Engineers, C, 60-579, 3769-3775 (1994). Katsuaki Saruwatari, Taiyo Miyata, Kazuto Sado, “Study on active sound insulation (control of flat plate noise)”, Transactions of the Japan Society of Mechanical Engineers, C, 61-590, 3916-3922 (1995). Johnson, M.E., Elliott, S.J .: Active control of sound radiation using volume velocity cancellation, J. Acoust. Soc. Am. 98 (4), 2174-2186 (1995) Henrioulle, K., Sas, P .: Experimental validation of a collocated PVDF volume velocity sensor / actuator pair, J. Sound Vib. 265, 489-506 (2003)

  The present invention has been made to solve the above-mentioned problems, and can not only exhibit excellent sound insulation performance for sound in a wide frequency band without causing control spillover, but also can be easily put into practical use. An active sound insulation device is provided. It is also an object of the present invention to provide an active sound insulation panel suitable for use in this active sound insulation device. It is another object of the present invention to provide an active sound insulation method using the active sound insulation device or the active sound insulation panel.

1.1 Theory of active sound insulation control In order to solve the above problems, we first performed a theoretical analysis of active sound insulation control. Fig. 2 shows a calculation model for active sound insulation control. In the following, as shown in Fig. 2, a thin plate embedded in an infinite baffle is assumed as a panel separating the sound source side and the sound receiving side, and sound (plane sound wave) is incident on this panel vertically We examine about. In this case, the equation of motion of the panel is expressed by the following formula 1.

Further, the vibration speed (v (r)) of the panel is expressed by the following formula 2 by the mode expansion formula when considering the Nth vibration mode.

At this time, the above formula 1 can be expressed by the following formula 5.

From the above, the speed mode vector v of the above equation 4 can be obtained by the following equation 11.

At this time, the acoustic power of the transmitted sound (W _T ) can be finally expressed by the following formula 14 by integrating the intensity on the panel.

Here, since the power matrix A is a real symmetric matrix, it can be diagonalized and can be expressed in the form of the following Expression 16.

Therefore, sound power W _T of the transmitted sound can be represented by the following formula 17.

From the above equation 18, the vibration speed v (r) of the panel is expressed by the following equation 19.

The above equation 17, the acoustic power W _T of the transmitted sound is represented can be seen in the square sum of the eigenvalues λ radiation mode amplitude weighted by _i u _i of the power matrix A corresponding to the radiation efficiency.

1.2 Acoustic power of transmitted sound during non-control Next, the acoustic power of transmitted sound during non-control will be discussed from the viewpoint of radiation mode. In this specification, “when not controlled” means that the actuator is not arranged on the panel and the panel is not vibrated by the actuator. On the other hand, when the actuator is arranged on the panel and the panel is vibrated by the actuator, it is called “during control”.

In the following, a case where a sound having an amplitude p _I is perpendicularly incident on the panel will be considered. Table 1 shows the specifications of the subject panels. Table 2 shows the vibration modes of the subject panel.

  FIG. 3 is a diagram showing the shapes of radiation modes from the first order to the third order at 100 Hz. The shape of the radiation mode in FIG. 3 is the result of calculation taking into consideration up to the ninth order of the [odd, odd] order vibration mode. In the case of normal incidence, since the sound pressure due to the incident sound is uniform on the panel, only the [odd, odd] order vibration mode is vibrated, so it is composed of the [odd, odd] order vibration mode. Only the radiation mode affects the transmitted sound. As shown in FIG. 3, the primary radiation mode is shaped so that the entire panel moves in a piston motion, and the secondary radiation mode and the third radiation mode are such that the edge portion of the panel vibrates. You can see that it has a shape. The primary radiation mode is equivalent to the panel volume velocity in the low frequency band.

FIG. 4 is a graph showing the relationship between the sound frequency and the sound transmission loss (R [dB]) when not controlled. The sound transmission loss R [dB] was obtained by calculation using Equation 21 below.

  FIG. 5 is a graph showing the relationship between the sound frequency, the acoustic power of the radiation modes from the first to the third order when not controlled, and the acoustic power of the totally transmitted sound. As can be seen from FIG. 5, in the low frequency band of about 800 Hz or less, the acoustic power of the primary radiation mode is overwhelmingly larger than the acoustic power of the other radiation modes, and is dominant in the acoustic power of all transmitted sound. It turns out that it is. This is because the radiation efficiency of the high-order radiation mode is low in a low frequency band having a relatively long wavelength. From this result, it is understood that the primary radiation mode, that is, the volume velocity may be reduced in order to suppress the low-frequency band transmitted sound.

In addition, as can be seen from FIG. 5, in the low frequency band, a phenomenon in which the acoustic power of the transmitted sound is minimized occurs at a specific frequency slightly lower than the resonance frequency at which the panel resonates. This phenomenon is called “anti-resonance” and can be explained as occurring due to a decrease in acoustic power due to the first-order radiation mode at the specific frequency. When all the actuators apply the same control force _fe to the panel, the primary radiation mode (u ₁ ) at the time of control can be expressed by the following expression 22 from the above expression 18.

As can be seen from Equation 22, the magnitude of the primary radiation mode (the absolute value of u _1c ) due to the excitation force of the actuator may be close to 0 at a specific frequency due to mode coupling. At this time, a control spillover in which the control effect by the actuator cannot be obtained appears.

  Mode coupling occurs between all modes, but in the low frequency band, the fundamental vibration mode ([1,1] order vibration mode) contributes the most in the primary radiation mode, which affects the transmitted sound. The combination of the fundamental vibration mode ([1,1] order vibration mode) and the higher order vibration mode ([1,3] order vibration mode, [3,1] order vibration mode, etc.) This is the case.

  FIG. 6 is a diagram showing a vibration distribution when the panel is vibrated at 159.5 Hz and 277.5 Hz, which are anti-resonance frequencies (frequency at which anti-resonance appears). The panel used was that whose specifications are shown in Table 1 above. At these anti-resonance frequencies, the center portion and the peripheral portion of the panel vibrate in opposite phases, so that nodal lines are formed in the panel. With such a vibration distribution, the sound generated in the central portion and the peripheral portion of the panel is canceled out, and the sound radiation efficiency is reduced. For this reason, it can be considered that the transmitted sound is reduced.

  Up to this point, the case where the peripheral edge of the panel is simply supported (support that restrains only the displacement) has been studied, but anti-resonance also appears in a general finite panel. Fig. 7 shows the sound frequency, the sound transmission loss R [dB] when the peripheral edge of the panel is simply supported, and the sound transmission loss R [when the peripheral edge of the panel is fixedly supported (support that restricts displacement and rotation). It is a graph showing the relationship with dB]. The sound transmission loss R [dB] was obtained by calculation using Equation 21 above. The panel used was that whose specifications are shown in Table 1 above.

  As can be seen from FIG. 7, when the peripheral edge of the panel is fixedly supported, the natural frequency of the panel is higher than when the peripheral edge of the panel is simply supported. Therefore, the frequency at which the sound transmission loss R [dB] is maximized or It can be seen that the minimum frequency is shifted to the high frequency side. However, it can be seen that the anti-resonance in which the sound transmission loss R [dB] is maximized in the low frequency band is the same when the peripheral edge of the panel is simply supported or when the peripheral edge of the panel is fixedly supported. .

  Moreover, although the case where the panel is a rectangle was examined so far, anti-resonance appears also in panels of other shapes. FIG. 8 is a diagram showing an example of a shape that can be adopted as a panel. FIG. 9 is a graph showing the relationship between the sound frequency and the sound transmission loss R [dB] during non-control when the panel having the shape shown in FIG. 8 is used. The specifications of the panel are the same as those in Table 1 except for the vertical length a and the horizontal length b. The sound transmission loss R [dB] was obtained by calculation using Equation 21 above. As can be seen from FIG. 9, an anti-resonance that maximizes the sound transmission loss occurs in the low frequency band regardless of the shape of the panel.

1.3 Acoustic power of transmitted sound during control Next, when the sound is incident perpendicularly to the non-controlled panel at a specific anti-resonance frequency (assuming ω _a ), Consider a case where an actuator is placed on _a nodal line (L _a ). In the following, it has an anti-resonant frequency for the anti-resonance by the primary vibration mode and j-th order vibration mode and the anti-resonant frequency omega _a.

In the anti-resonance frequency omega _a, since the influence of the specific oscillation mode Coupled with fundamental vibration mode (first vibration mode) (j order vibration mode) is large, here, ignoring the effect of the other vibration mode it can. At this time, the volume velocity V at the time of non-control can be expressed by the following Equation 23.

At this time, the mode excitation force F _I by the incident sound is represented by the following formula 24.

Therefore, from the above equation 23 and the equation 24, as the relationship of the volume velocity V and mode excitation force F _I, the following equation 25 is obtained.

At the anti-resonance frequency ω _a , the primary radiation mode is minimal, so the volume velocity V equivalent to the primary radiation mode at a low frequency is also minimal. Therefore, at the anti-resonance frequency ω _a , the following equation 26 is obtained.

That is, the volume velocity V is determined when the primary velocity mode amplitude v _I1 , the j-th velocity mode amplitude v _Ij , the primary vibration mode excitation force F _I1 and the j-order vibration mode excitation force F _Ij satisfy the following formula 27. Therefore, it can be said that anti-resonance appears.

Next, consider the excitation force by the actuator. The excitation force of M actuators (point actuators) that generate the same excitation force can be expressed by the following Equation 28.

At this time, the above formula 10 can be expressed by the following formula 29.

At this time, the following equation 31 is obtained from the above equation 29.

Here, since all the actuators are thinking about a case which is arranged on the nodal line planned line L _a, the following equation 32 is established.

Therefore, the above equation 31 becomes the following equation 33.

Here too, it is considered that the influence of a specific vibration mode (j-th vibration mode) coupled with the fundamental vibration mode ([1,1] -order vibration mode) is large, and considering only these, the following equation 34 is obtained.

Therefore, the following formula 35 is obtained from the above formula 27 and the above formula 34.

Thus, the panel by disposing the actuator on the nodal line planned line L _a of the nodal lines when anti-resonance at the anti-resonant frequency omega _a, the two vibration modes that are involved in anti-resonant modes pressurized The ratio of the vibration force can be matched with the ratio of the mode excitation force by the incident sound wave. That is, an excitation force equivalent to the excitation force caused by the incident sound can be applied from the actuator to the panel.

From the above, the present inventors are concerned with the panel for separating the sound source side and the sound receiving side, the sensor for detecting the sound emitted from the sound source or the vibration of the panel, and the sound or vibration detected by the sensor. An active sound insulation device comprising: control means for generating a control signal in response; and an actuator for suppressing the transmitted sound of the panel by exciting a predetermined portion of the panel based on the control signal generated by the control means. An actuator is arranged at least at one point on the nodal line L _a in the panel that becomes a nodal line when the sound is vertically incident on the control panel and anti-resonant at the anti-resonance frequency ω _a It came to propose the active sound insulation device characterized by this.

  As a result, it is possible to obtain an active sound insulation device capable of exhibiting excellent sound insulation performance against a wide frequency band sound (particularly a low frequency band sound that is difficult to be insulated with a soundproof material).

  The active sound insulation device of the present invention is shipped not only when the panel, sensor, control means, actuator, and other necessary items are shipped as a set, but also as a panel with an actuator (active sound insulation panel). Cases are also envisioned.

That is, an active sound insulation panel in which an actuator that suppresses the transmitted sound of the panel by vibrating the panel at a predetermined position of the panel for separating the sound source side and the sound receiving side is attached to the non-control panel. active, characterized in that the actuator is arranged on at least one point on the nodal lines planned line L _a in the panel as a nodal lines upon by anti-resonance of the sound vertically incident allowed by the anti-resonance frequency omega _a Te It is a sound insulation panel. In this case, the purchaser of the active sound insulation panel can appropriately select other than the panel and the actuator.

  In addition to the actuator, other devices and parts can be attached to the active sound insulation panel. For example, it is assumed that in addition to the actuator, a sensor for detecting sound emitted from a sound source or vibration of the panel is shipped with the panel attached. In this case, it is preferable to employ a sensor that detects panel vibration. Specifically, it is assumed that a piezoelectric film such as a PVDF film is attached to the panel as a sensor before shipment. Piezoelectric films such as PVDF films that are currently available on the market are weak in generating force, and thus have many problems in practical use as actuators, but they can be practically used as sensors.

  Thus, by integrating the panel and the sensor, it is possible to reduce the trouble of installing the sensor when constructing the active sound insulation panel. Further, even in a situation where it is difficult to install a sensor at a position away from the panel, active sound insulation control can be performed. Furthermore, when a sensor that detects sound is used, noise around the construction site of the active sound insulation panel may adversely affect the active sound insulation control. By using a device that detects noise, it is possible to prevent noise from adversely affecting the active sound insulation control.

  Furthermore, by attaching a piezoelectric film such as PVDF film to the panel as a sensor, it is possible to directly detect the primary radiation mode equivalent to the acoustic power of transmitted sound (transmitted acoustic power). Thus, the control effect of the active sound insulation control can be sufficiently exhibited. On the other hand, when using a sensor that detects sound, such as a microphone, and performing feedforward control, which will be described later, the sensor was placed even though it was originally necessary to minimize the transmitted acoustic power. Since the control is to minimize the sound pressure at the place, the control effect may be halved depending on the conditions.

  In addition to the actuator and the sensor, the active sound insulation panel is assumed to be shipped with a control unit that generates a control signal according to sound or vibration detected by the sensor attached to the panel. This configuration is particularly realistic when a piezoelectric film such as a PVDF film is used as a sensor and feedback control described later is performed. In the case of feedback control, it is not necessary to refer to the signal of the sound source, so that not only the actuator and sensor, but also the control means are integrated into the panel and active sound insulation control can be performed independently by itself. This is because the panel can be realized relatively easily.

Subsequently, _a node that becomes a nodal line when a sound is vertically incident on the non-control panel and is anti-resonant at another anti-resonance frequency (referred to as ω _b ) higher than the anti-resonance frequency ω a. Consider a case where an actuator is placed on _a planned line (referred to as La). In the following, the antiresonance frequency of the antiresonance in the primary vibration mode and the kth vibration mode (k is an integer greater than j) is defined as antiresonance ω _b . In this case, the following formula 36 is obtained by the same procedure as the above formula 35.

Furthermore, the joint line will line L _a of the nodal lines in the sound with respect to the panel in the non-control was anti-resonance in is incident perpendicularly anti-resonance frequency omega _a, another higher than anti-resonance frequency omega _a consider the case which arranged the actuator at the intersection of the section line will line L _b which is a nodal lines when was anti-resonance at the anti-resonance frequency ω _b of. In this case, the following formula 37 is obtained by the above formula 35 and the above formula 36.

Thus, by arranging the actuator at the intersection of the joint line will line L _a and joint line will line L _b, match the mode excitation force by the actuator, the mode excitation force due to the incident wave for the three vibration modes Can be made.

Further, as can be seen from the above equation 22, if the mode excitation force F _I caused by the sound incident on the panel can be matched with the mode excitation force F _c caused by the actuator, a wide frequency can be obtained without causing a control spillover. The primary radiation mode can be efficiently suppressed in the band.

For all vibration modes, it is difficult to match the mode excitation force F _I and the mode excitation force F _c , but match the terms of the lower-order vibration modes that have a large effect on the total transmitted sound. If possible, it is considered that a sufficient control effect can be obtained even in a low frequency band.

From the above, the present inventors, the joint line will line L _a at the non-control time is incident perpendicularly sounds against a panel of the nodal lines when was antiresonance antiresonance frequency omega _a the panel Of the intersections with the nodal line L _{b in the} panel that becomes the nodal line when the sound is vertically incident on the non-control panel and anti-resonant at the antiresonance frequency ω _b (> ω _a ) It was concluded that it is preferable to arrange the actuator at at least one point.

  As a result, it is possible to exert a control effect by the actuator for sounds in a wide frequency band.

However, it is not always possible to obtain a large control effect simply by arranging the actuator on the planned nodal line at the anti-resonance frequency. For example, when the actuator is placed at one point on the nodal line when the panel is vibrated at its anti-resonance frequency of 159.5 Hz, the [1,1] order vibration mode and the [1,1] 3] in the following vibration mode, since the mode excitation force F _I a plane wave incident on the panel, and a mode excitation force F _C by the actuator becomes equal, the primary radiation mode can be suppressed. However, at the same time, the [odd, even] order vibration mode, [even, odd] order vibration mode, and [even number, even] order vibration mode that did not significantly affect the transmitted sound when not controlled were excited Since the contribution of the radiation mode increases, the control effect is limited.

  In the following, it is divided by the contour line of the panel and the nodal line as in the [odd, even] order vibration mode, [even, odd] order vibration mode and [even, even] order vibration mode in the rectangular panel. The total number of areas is an even number, and the vibration mode of the order in which the number of areas that vibrate in a certain same phase and the number of areas that vibrate in the same phase opposite to that area coincides with the “cancellation type vibration mode May be called.

  On the other hand, the total number of areas divided by the contour lines and nodal lines of the panel is odd, such as the [odd, odd] order vibration mode in a rectangular panel, and the number of areas that vibrate in a certain phase A vibration mode having an order different from the number of areas that vibrate in the same phase opposite to the area may be referred to as a “non-cancellation type vibration mode”.

  In the cancellation type vibration mode, since the sound suction and discharge in the panel are almost equal, there is a tendency that the primary radiation mode is hardly affected. The suction and discharge of water are not equal and tend to have a great influence on the primary radiation mode.

From the above, the present inventors, among the points on the nodal lines planned line L _a, and concluded that preferable to distribution of the actuator to a point overlapping the nodal lines of the low-order cancellation type vibration mode. As a result, it is possible to make it difficult for the low-order canceling vibration mode that does not significantly affect the transmitted sound during non-control to be excited during control.

The order of the cancellation type vibration mode selected at this time (the order counted from the lowest natural frequency among all cancellation type vibration modes) is the non-cancellation type vibration mode that couples the anti-resonance at the anti-resonance frequency ω _a. Depends on the order of. More specifically, among the non-cancellation type vibration modes coupled with anti-resonance at the anti-resonance frequency ω _a , the natural frequency is in the same frequency band as the resonance frequency of the non-cancellation type vibration mode having the highest natural frequency. A cancellation type vibration mode having a lower order than that of the cancellation type vibration mode having is selected.

For example, the horizontal length is longer than the horizontal length (in this specification, the vertical length a (the length in the x-axis direction of the panel (see FIG. 1)). Using the rectangular panel of length b (the length of the panel in the y-axis direction (see Fig. 1)) is called "landscape", the vibration mode is shown in Table 2 above. 1st order non-cancellation type vibration mode ([1,1] order vibration mode with natural frequency 46.3Hz) and 2nd order non-cancellation type vibration mode ([1,3 with natural frequency 169.8Hz) If the anti-resonance frequency at the time of anti-resonance due to coupling with the [next-order vibration mode] is selected as the anti-resonance frequency ω _a , is it close to 169.8 Hz, which is the natural frequency of the [1,3] -order vibration mode 1st cancellation type vibration mode ([1,2] order vibration mode with natural frequency 92.6Hz), 2nd order cancellation type vibration mode (with natural frequency 138.9Hz [ 2,1] Vibration mode), it is preferable to consider the third order cancellation-type vibration mode ([2,2] the following vibration mode of the natural frequency 185.2Hz).

However, the positional relationship between the plurality of nodal lines of the canceling vibration mode cancellation type oscillation mode and the positional relationship and joint line will line L _a between nodal lines of, when considering the further actuator of cost and installation space, a problem It is difficult to place the actuator on the nodal line of all the low-order canceling vibration modes. In such a case, a method that does not excite the cancellation type vibration mode by using the symmetry of the panel can be considered. That is, the panel shall have a point symmetrical shape or line symmetry shape, among the points on the nodal lines planned line L _a, the line-symmetrical position with respect to the straight line passing through the point-symmetrical or said center relative to the center of the panel In this method, actuators are arranged at at least two points.

  For example, at the point where the actuator is arranged in the arrangement A of FIG. 11, the nodal line of the second order cancellation type vibration mode ([2,1] order vibration mode) and the third order cancellation type vibration mode ([2,2, 2) The secondary vibration mode) node passes, but the primary cancellation type vibration mode ([1,2] order vibration mode) does not pass. However, the two actuators are arranged in a line-symmetrical position with respect to the x-axis (the center of the panel is the origin), so by exciting with the same force, the primary cancellation type vibration mode It is also possible to prevent excitation.

  Thus, by devising the arrangement of the actuators, the cancellation type vibration mode (especially the low-order cancellation type vibration mode) that did not significantly affect the transmitted sound during non-control is prevented from being excited during control. be able to. Therefore, the sound insulation performance of the active sound insulation device can be further improved.

  By the way, when the sound is incident on the panel obliquely (obliquely incident), the cancellation type vibration mode which is not excited when the sound is incident vertically (perpendicularly incident) on the panel is large in the transmitted sound. It comes to influence.

  Therefore, it is preferable that the panel loss coefficient η be as large as possible. Thereby, even in the case of oblique incidence, the cancellation type vibration mode can be made difficult to be excited, so that excellent sound insulation performance can be obtained regardless of the direction of sound incidence on the panel. Specifically, the panel loss coefficient η is preferably 0.05 or more.

  In addition, when the area of the boundary surface between the sound source side and the sound receiving side is large, it is necessary to increase the area of the panel, but in this case, it is difficult to obtain a control effect for high frequency sound. . This is because the natural frequency of the panel decreases as the area of the panel increases, and the frequency band in which the control effect by the actuator is obtained shifts to the low frequency side.

Therefore, when it is necessary to widen the area of the panel, the panel is divided into a plurality of small panels, it is preferable to arrange the actuator in at least one point on the nodal lines planned line L _a in each of the small panels. As a result, even when the area of the boundary surface between the sound source side and the sound receiving side is large, it is possible to block a sound having a high frequency.

  As described above, according to the present invention, it is possible to provide an active sound insulation device that not only exhibits excellent sound insulation performance for sounds in a wide frequency band without causing a control spillover, but also can be easily put into practical use. Is possible. It is also possible to provide an active sound insulation panel that can be suitably used for this active sound insulation device. Furthermore, it is also possible to provide an active sound insulation method using this active sound insulation device.

2 Specific Embodiment of Active Sound Insulation Device of the Present Invention A specific embodiment of the active sound insulation device of the present invention will be described in detail with reference to the drawings. FIG. 10 is a diagram showing an example of the active sound insulation device of the present invention.

  As shown in FIG. 10, the active sound insulation device of the present embodiment includes a panel for separating the sound source side and the sound receiving side, a sensor for detecting the sound emitted from the sound source, and the sound detected by the sensor. Control means for emitting a control signal, and an actuator for suppressing the transmitted sound of the panel by exciting a predetermined portion of the panel based on the control signal issued by the control means. In the active sound insulation device according to the present embodiment, the panel has the specifications shown in Table 1 above.

2.1 Sensor Examples of sensors include those that can detect sound emitted by a sound source and those that can detect panel vibration. A microphone is exemplified as a sensor that detects sound emitted by a sound source. Examples of sensors that detect panel vibration include piezoelectric elements such as acceleration pickups and PVDF films. In the active sound insulation device of this embodiment, a microphone is used as the sensor.

  The location of the sensor is not particularly limited. The sensor may be arranged on the sound source side, or may be arranged on the sound receiving side (or in close contact with the panel). In the former case, the incident sound incident on the panel is detected by a sensor, the sound is fed forward to the control means, and the vibration of the panel is controlled by the actuator based on the control signal generated by the control means. Such control is called “feedforward control”.

  On the other hand, in the latter case, the sound transmitted through the panel or the vibration of the panel is detected by the sensor, the sound or vibration is fed back to the control means, and the actuator is controlled by the actuator based on the control signal generated by the control means. Vibration will be controlled. Such control is called “feedback control”.

  The active sound insulation device of the present invention is effective in both feedforward control and feedback control. In the active sound insulation device of this embodiment, the case of feedforward control is described for convenience of explanation.

2.2 Control means The control means is not particularly limited as long as it can generate a control signal according to the sound detected by the sensor. Examples of the control means include a digital signal processing device. In the active sound insulation device of this embodiment, a digital signal processing device comprising a DSP board, a D / A board, and an A / D board is used as a control means.

  Various algorithms used for active sound insulation control can be used as the control algorithm of the control means. Examples of the control algorithm of the control means include “Filtered-X LMS algorithm”, “Phase corrected filtered error LMS algorithm”, “optimum algorithm”, “H∞ control algorithm”, and the like. In the active sound insulation device of this embodiment, the “Filtered-X LMS algorithm” is adopted.

2.3 Actuator The type of actuator is not particularly limited, but a point actuator that can locally excite a specific point on the panel is usually used. In the active sound insulation device of this embodiment, a voice coil type point actuator is used as the actuator.

The actuator is placed at least at one point on the nodal line L _a on the panel that becomes a nodal line when the sound is incident perpendicularly to the non-control panel and anti-resonant at the anti-resonance frequency ω _a. If arranged, it will not be specifically limited. For example, the arrangements A to C shown in FIG. 11 can be employed. FIG. 11 is a diagram for explaining how the actuators are arranged in the active sound insulation device of the present invention.

Among the arrangements A to C shown in FIG. 11, the arrangement A is obtained when the sound is vertically incident on the non-control panel and anti-resonant at an anti-resonance frequency ω _a (159.5 Hz). each respective midpoints of the two nodal lines planned line L _a in the panel as a nodal lines has become that arranged actuator. The two nodal line lines L _{b in the} panel that becomes the nodal line when the sound is incident vertically on the non-control panel and anti-resonant at the anti-resonance frequency ω _b (277.5 Hz) are does not pass through the midpoint of the section line will line L _a.

In addition, the arrangement B has two nodes in the panel that become nodal lines when the sound is vertically incident on the non-control panel and anti-resonant at the anti-resonance frequency ω _a (159.5 Hz). the line will line L _a, is incident vertically sound to the panel in the non-controlled anti-resonant frequency omega _b (the 277.5Hz.) at the time obtained by the anti-resonance of the two in the panel as a nodal lines It has become a thing which arranged the actuator to one of the four intersections of the nodal lines will line L _b.

Furthermore, the arrangement C has two nodes in the panel that become nodal lines when the sound is vertically incident on the non-control panel and anti-resonant at the anti-resonance frequency ω _a (159.5 Hz). the line will line L _a, is incident vertically sound to the panel in the non-controlled anti-resonant frequency omega _b (the 277.5Hz.) at the time obtained by the anti-resonance of the two in the panel as a nodal lines It has become a thing which arranged the actuator to all of the four intersections of the nodal lines will line L _b.

In determining the arrangement of the actuator, there is no particular limitation on which of the plurality of anti-resonance frequencies is selected as the anti-resonance frequency ω _a or the anti-resonance frequency ω _b . However, in consideration of the control effect on the sound in the low frequency band, it is preferable to select an anti-resonance frequency at the time of anti-resonance by coupling between the lowest order non-cancellation vibration modes.

  This is because, as already stated, in the low frequency band, the transmitted acoustic power by the first radiation mode is overwhelmingly larger than the transmitted acoustic power by the other radiation modes and is dominant in the total transmitted acoustic power. However, in this primary radiation mode, the contribution of the vibration mode tends to increase as the order of the non-cancellation vibration mode constituting the radiation mode decreases.

  The order of the non-cancellation type vibration mode selected at this time (the order counted from the lowest natural frequency among all the non-cancellation type vibration modes) is not particularly limited, but is usually 10th or less. The order of the non-cancellation type vibration mode is preferably 5th order or less, more preferably 3rd order or less (for example, when the panel is a horizontally long rectangle, the 1st order ([1,1] order), 2nd order ([1,3] order) or 3rd order ([3,1] order)).

When the panel is a horizontally long rectangle as in the active sound insulation device of the present embodiment, the primary non-cancellation type vibration mode ([1,1] order vibration mode) and the secondary non-cancellation type vibration mode The anti-resonance frequency ω _a is selected as the anti-resonance frequency ω _a when anti-resonant by coupling with ([1,3] -order vibration mode), and the first non-cancellation type vibration mode ([1,1] -order vibration Mode) and the third order non-cancellation type vibration mode ([3,1] order vibration mode), it is optimal to select the antiresonance frequency at the time of antiresonance as the antiresonance frequency ω _b .

Also arranged A~C in FIG. 11, as [1,1] Next vibration mode and [1,3] antiresonance frequency antiresonant frequency (159.5Hz) when anti-resonance by Coupling of the next oscillation mode omega _a The anti-resonance frequency (277.5Hz) at the time of anti-resonance by coupling [1,1] order vibration mode and [3,1] order vibration mode is adopted as anti-resonance frequency ω _b .

  By the way, among the arrangements A to C, the arrangement A and the arrangement C are point-symmetric with respect to the center of the panel and the actuator is arranged at a line-symmetrical position with respect to a straight line passing through the center. By arranging actuators with the same excitation force and excitation direction in this way, low-order canceling vibration modes with low radiation efficiency that did not significantly affect the transmitted sound during non-control are excited during control. It becomes possible to make it difficult.

  Such an arrangement is possible even if the panel has a shape other than a rectangle as long as the panel has a point-symmetrical shape or a line-symmetrical shape. For example, as shown in FIG. 8, even when the panel is (a) circular, (b) oval, (c) hexagon, (d) hourglass, By arranging the actuator at a line-symmetrical position with respect to a straight line passing through the center, it is possible to make the cancellation type vibration mode difficult to be excited during control.

  On the other hand, as shown in Fig. 8 (e), when the panel is irregular and does not have either a point-symmetrical shape or a line-symmetrical shape, mode analysis by the finite element method, experimental mode analysis, etc. The shape of the radiation mode is obtained in advance, and the actuator may be arranged at a position where the low-order canceling vibration mode with low radiation efficiency is not excited.

The anti-resonance frequencies that can be used as the anti-resonance frequencies ω _a and ω _b and the no-node planned lines that can be used as the no-node planned lines L _a and L _b are logical when the panel boundary conditions are clear. Although it can be determined, in reality, it is expected that it is difficult to determine theoretically because boundary conditions and the like are unclear. In such a case, a method for experimentally finding the anti-resonance frequency and the nodal line is considered. A specific procedure for experimentally finding the anti-resonance frequency and the nodal line is described below.

First, sound is incident perpendicularly to the panel and the transmitted acoustic power is measured, and the frequency at which the transmitted acoustic power is minimized is obtained. If the sound transmission power is maximized at a frequency slightly higher than that frequency, the frequency at which the transmission sound power is minimized is the anti-resonance frequency. In general, there are a plurality of anti-resonance frequencies. Among these anti-resonance frequencies, which one is adopted as the anti-resonance frequencies ω _a and ω _b is as described above.

Next, the vibration distribution of the panel at the found anti-resonance frequencies ω _a and ω _b is measured by a vibration acceleration sensor and a laser Doppler vibrometer to find a point where the panel does not vibrate. The vibration distribution of the panel can also be obtained from the transmitted sound using an acoustic holography device. The set of points that do not vibrate become the nodal lines L _a and L _{b at the} antiresonance frequencies ω _a and ω _b . A point that does not vibrate can also be found by performing an actual motion analysis.

2.4 Panel The type of panel is appropriately determined in consideration of the type of sound source and the environment in which the active sound insulation device is installed. In consideration of sound insulation and durability, a metal plate such as aluminum is often used for the panel. Also in the active sound insulation device of this embodiment, the aluminum plate shown in Table 1 is used as a panel.

  The area of the panel is appropriately determined in consideration of the frequency of the sound for which a control effect is desired. In general, as the panel area increases, the frequency band where the control effect can be obtained shifts to the low frequency side, and as the panel area decreases, the frequency band where the control effect can be obtained shifts to the high frequency side. For this reason, when the area of a panel becomes large, it becomes difficult to insulate the sound of a comparatively high frequency band.

  Therefore, if there is a situation where the area of the panel needs to be widened, such as the area of the part to be sound-insulated is wide, and the sound of high frequencies needs to be sound-insulated, the thickness of the panel It is necessary to take measures to increase the natural frequency of the panel, such as increasing the thickness of h and forming the panel with a highly rigid material.

Further, the panel is divided into a plurality of small panels, it is also preferable to arrange the actuator nodal lines planned line L _a and joint line will line L _b in each of the small panels. FIG. 21 is a diagram showing a state in which the panel is divided into a plurality of small panels and an actuator is arranged on each of the small panels. As a result, it is possible to suppress relatively high frequency sound even when there are special circumstances such as the panel cannot be thickened or the rigidity of the panel cannot be increased.

The shape of the small panel is not particularly limited, but is usually a shape that can be spread, such as a quadrangle, a triangle, or a regular hexagon. As a result, the boundary surface between the sound source side and the sound receiving side can be filled with a small panel without a gap. Each of the small panel may have different shapes, but in this case, not only labor required for installation of the active sound insulation device increases, the position of the joint line will line L _a and joint line will line L _b Since it is different for each small panel, labor for mounting the actuator is also increased. For this reason, unless there are special circumstances such as irregular interface between the sound source side and the sound receiving side, the respective small panels are usually formed in the same shape.

  When the panel is divided into a plurality of small panels, one or a plurality of sensors and control means may be provided for each small panel. However, in this case, the production cost of the active sound insulation device may increase significantly. For this reason, unless there are special circumstances such as the large boundary between the sound source side and the sound receiving side and the nature of the incident sound differing greatly depending on the position of the small panel, the sensor and the control means are usually all small panels. One by one.

3 Application Examples Specific application examples of the active sound insulation device and the active sound insulation method of the present invention are not particularly limited. It can be applied to various scenes where a panel can be arranged between the sound source side and the sound receiving side. In the following, some applications suitable for using the active sound insulation device and the active sound insulation method of the present invention will be introduced.

3.1 Application example 1
The active sound insulation device and the active sound insulation method of the present invention can be applied to a soundproof box for reducing external sound and keeping the interior quiet. FIG. 26 is a diagram showing an example in which the active sound insulation device and the active sound insulation method of the present invention are applied to a soundproof box. In FIG. 26, a scanning probe microscope (SPM) is accommodated in the soundproof box. In addition, it can also be applied to soundproof boxes to prevent sounds emitted by engines and compressors from leaking outside.

3.2 Application 2
The active sound insulation device and the active sound insulation method of the present invention can also be applied to buildings. FIG. 27 is a diagram showing an example in which the active sound insulation device and the active sound insulation method of the present invention are applied to a wall partitioning a room in a building. FIG. 28 is a diagram showing an example in which the active sound insulation device and the active sound insulation method of the present invention are applied to an outer wall in a building. In addition, it can be applied to doors, windows, ceilings, floors, etc.

3.3 Application 3
The active sound insulation device and the active sound insulation method of the present invention can also be applied to a vehicle. FIG. 29 is a diagram showing an example in which the active sound insulation device and the active sound insulation method of the present invention are applied to an aircraft. In addition, it can be applied to railway vehicles and automobiles.

4 Verification of sound insulation performance by calculation Subsequently, the sound insulation performance of the active sound insulation device and the active sound insulation method of the present invention was verified by calculation. In the following, conditions such as panel dimensions and materials, actuator type, control algorithm of control means, etc. are the same as those adopted in “2 Specific Embodiment of Active Sound Insulation Device of the Present Invention” unless otherwise specified. is there.

4.1 Effects of actuator placement First, the acoustic transmission loss is calculated for each of the cases where the actuator is placed in the positions A to C in Fig. 11 and when the actuator is not placed (when not controlled). I asked for it. Here, in order to examine the control effect that is ideally obtained, the sound transmission loss was calculated when the optimum feedforward control law that minimizes the transmitted sound power was applied.

  12 shows the sound transmission loss when the sound is vertically incident on the panel in which the actuator is arranged in the arrangements A to C in FIG. 11 and when the sound is vertically incident on the panel when not controlled. The calculation result of is shown. Referring to FIG. 12, it can be seen that in both the arrangement A and the arrangement C, a very large control effect can be obtained in a wide frequency band as compared with the case of non-control. Further, comparing the arrangement A and the arrangement C, it can be seen that the arrangement C has a control effect up to a high frequency band.

  In the case of arrangement A, the excitation force by the actuator and the excitation force of the sound incident on the panel are equal to each other in the [1,1] -order vibration mode and the [1,3] -order vibration mode. In the case of Arrangement C, in addition to the vibration mode only, the excitation force by the actuator is available in the [1,1] -order vibration mode and [1,3] -order vibration mode as well as in the [3,1] -order vibration mode This is because the excitation force of the sound incident on the panel becomes equal.

  On the other hand, when looking at the calculation result of the arrangement B, a certain control effect can be obtained compared to the case of non-control, but the control effect is limited compared to the arrangement A and the arrangement C. ing. This is because the cancellation type vibration mode, which originally had low radiation efficiency in the low frequency band and had little influence on the transmitted sound, was excited.

4.2 Comparison of the Present Invention with the Prior Art by Calculation Subsequently, in order to compare the active sound insulation device of the present invention with the conventional active sound insulation device, the same calculation was performed with the arrangements C to G shown in FIG. FIG. 13 is a diagram showing the arrangement of the actuator with respect to the panel.

  Arrangement C is the same as arrangement C shown in FIG. 11 (four-point control of the present invention).

  In the arrangement D, an actuator is arranged at the center of the panel ((0,0) as (x coordinate, y coordinate) (conventional one point control).

  Arrangement E is (-a / 3, -b / 3), (-a / 3, b / 3), ((x-coordinate, y-coordinate) as four points (outside of arrangement C) a / 3, -b / 3), (a / 3, b / 3)) with actuators (conventional 4-point control). All four actuators have the same excitation force and direction.

  Arrangement F is 16 points (x coordinate, y coordinate) (-3a / 8, -3b / 8), (-3a / 8, -b / 8), (-3a / 8) , b / 8), (-3a / 8, 3b / 8), (-a / 8, -3b / 8), (-a / 8, -b / 8), (-a / 8, b / 8) ), (-a / 8, 3b / 8), (a / 8, -3b / 8), (a / 8, -b / 8), (a / 8, b / 8), (a / 8, 3b / 8), (3a / 8, -3b / 8), (3a / 8, -b / 8), (3a / 8, b / 8), (3a / 8, 3b / 8))) (Conventional 16-point control). The excitation force and direction of the 16 actuators are all equal.

  Arrangement G has 6 points ((x coordinate, y coordinate) (-a / 6, -b / 3), (-a / 6,0), (-a / 6, b / 3), (a / 6, -b / 3), (a / 6,0), (a / 6, b / 3)) with actuators. The excitation forces of the six actuators are all equal, but (-a / 6, -b / 3), (-a / 6, b / 3), (a / 6, -b / 3), (a / 6, b / 3)) and the excitation directions of the four actuators arranged in (-a / 6,0) and (a / 6,0) are The reverse is true. The arrangement G can approximately excite the [1,3] order vibration mode in the low frequency band.

  14 shows the sound frequency, sound transmission loss when the sound is vertically incident on the panel in which the actuators are arranged in arrangements C to G in FIG. 13, and the sound perpendicular to the panel when not controlled. It is the graph which showed the relationship with the sound transmission loss in the case of making it inject into.

  As can be seen from FIG. 14, in the band where the frequency is 100 Hz or less, a remarkable control effect is obtained in all of the arrangements C to G as compared with the case of non-control. However, when the frequency is higher than that, it can be seen that in the arrangements D to F, there is a frequency at which the control effect cannot be obtained. In addition, the arrangement G is inferior in control effect compared to the arrangements D to F in the frequency band of 100 Hz or less, but a constant control effect is obtained over a relatively wide frequency band. I understand.

  On the other hand, in the arrangement C, it can be seen that control effects superior to the arrangements D to G are obtained in almost all frequency bands. Even in the arrangement C, there is a frequency at which the control effect is reduced, but since this frequency matches the anti-resonance frequency, there is no problem. This is because at the anti-resonance frequency, the panel exhibits excellent sound insulation performance even if the control effect by the actuator is not obtained.

  From the above results, it has been found that the present invention provides a very remarkable control effect over a wide range of low frequency bands.

  FIG. 15 shows the frequency of sound, the mean square speed of the panel (square mean of vibration speed v) when the sound is vertically incident on the panel in which the actuators are arranged in arrangements C to G in FIG. It is the graph which showed the root mean square speed | velocity | rate of the panel at the time of making a sound vertically inject with respect to the panel at the time of control. FIG. 16 shows the sound frequency, the radiation efficiency when the sound is vertically incident on the panel in which the actuators are arranged in the arrangements C to G in FIG. 13, and the sound on the panel when not controlled. It is the graph which showed the relationship with the radiation efficiency at the time of making it enter perpendicularly.

  As can be seen from FIG. 15, in the arrangement C, the vibration speed v is greatly reduced in the low frequency band as compared with the case of non-control. On the other hand, in arrangements D to G, it can be seen that even in the low frequency band, there is a frequency at which the vibration velocity v increases compared to the case of non-control. In addition, when FIG. 16 is viewed, it can be seen that in the arrangement C, the radiation efficiency is reduced in a wide frequency band as compared with the non-control and the arrangements D to G.

  From the above results, it was found that in the arrangement C, both the vibration of the panel and the radiation efficiency are suppressed, and a large control effect can be obtained by the present invention.

4.3 Effects of panel material Next, we examined how the panel material affects the actuator control effect. In order to perform this verification, first, the panel thickness h was changed to 1 mm, 2 mm, 3 mm, and 5 mm, and the value of the sound transmission loss at each thickness h was obtained by calculation.

  FIG. 17 is a graph showing the relationship between the sound frequency and the sound transmission loss during non-control when the panel thickness h is changed to 1 mm, 2 mm, 3 mm, and 5 mm. FIG. 18 is a graph showing the relationship between the sound frequency and the sound transmission loss during control when the panel thickness h is changed to 1 mm, 2 mm, 3 mm, and 5 mm.

  As can be seen from FIG. 18, by increasing the thickness h, the frequency band where the control effect is obtained shifts to the high frequency side. This phenomenon can be explained as follows.

  As already mentioned, in arrangement C, in the [1,1] -order vibration mode, [1,3] -order vibration mode and [3,1] -order vibration mode, the excitation force by the actuator and the incident sound incident on the panel It was possible to equalize the excitation force by. That is, the frequency band in which the control effect is obtained is a frequency band in which these low-order non-cancellation vibration modes have a great influence on the transmitted sound. That is, the control effect can be obtained in a region below the resonance frequency of the [3, 1] order vibration mode. Therefore, it is considered that by increasing the thickness of the panel, the resonance frequency of the panel is increased and the frequency band in which the control effect is obtained is also shifted to the high frequency side.

Further, when the panel is thickened, the mass per unit area (surface density) of the panel is also increased, so that the sound transmission loss is generally increased. When the Young's modulus E of the panel is increased, the rigidity of the panel is increased, so that the resonance frequency is increased, and the frequency band in which the control effect is obtained is shifted to the high frequency side as in the case where the panel is thickened. When the panel density ρ _S is decreased, the surface density of the panel is decreased, the sound transmission loss is decreased as a whole, and the mode mass is also decreased, so that the resonance frequency is increased.

  From the above, it was confirmed that when the panel is thickened, the frequency band where the control effect is obtained shifts to the high frequency side. It was also found that changing the panel material changes the frequency band where the control effect can be obtained.

4.4 Verification of influence due to panel dimensions Next, we examined how the panel area affects the control effect of the actuator. Fig. 19 shows the non-frequency values when the sound frequency and the thickness h of a large panel (vertical length a is 0.8m, horizontal length b is 1.1314m) are changed to 1mm, 2mm, 3mm, and 5mm. It is the graph which showed the relationship with the sound transmission loss at the time of control. Also, Fig. 20 shows the case where the sound frequency and the thickness h of the large panel (vertical length a is 0.8m, horizontal length b is 1.1314m) are changed to 1mm, 2mm, 3mm and 5mm. It is the graph which showed the relationship with the sound transmission loss at the time of control.

  Comparing FIG. 18 and FIG. 20, it can be seen that as the panel area increases, the frequency band where the control effect is obtained shifts to the lower frequency side. This is due to a decrease in the natural frequency due to an increase in the panel area. When the panel is a horizontally long rectangle, as described above, the control effect can be obtained in a frequency band below the resonance frequency of the [3, 1] order vibration mode. Therefore, when the area of the panel is increased and the natural frequency is lowered, the frequency at which the control effect can be obtained also decreases.

  From the above, in order to obtain a control effect up to a high frequency while widening the panel area, it is only necessary to increase the natural frequency of the plate, such as thickening the panel or using a material with high specific rigidity. If the panel cannot be thickened, a method of dividing the panel into small areas and controlling each small panel as shown in FIG.

4.5 In the case of oblique incidence Up to this point, we have examined the case where sound enters the panel vertically (normal incidence). However, in the following, the case where sound enters the panel obliquely (oblique incidence). consider.

  In the case of oblique incidence, the vibration mode that is not excited in the case of normal incidence has an effect on the transmitted sound, so that the control effect by the actuator may be reduced. For example, if the panel is rectangular, only [odd, odd] order vibration mode is excited in the case of normal incidence, whereas [odd, even] order vibration mode in the case of oblique incidence, [ The even or odd order vibration mode or the [even, even] order vibration mode is excited.

  In order to investigate this effect, sound transmission loss was obtained by calculation in the case of oblique incidence. Figure 22 shows the sound transmission loss and the sound transmission loss during normal control when the sound frequency and the sound incident angle on the panel are changed to 0 ° (vertical incidence), 15 °, 30 °, and 60 °. It is the graph which showed the relationship with the sound transmission loss at the time of non-control at the time of letting it be.

  Referring to FIG. 22, it can be seen that the sound transmission loss decreases as the incident angle of sound with respect to the panel increases. However, it can also be seen that the control effect by the actuator is sufficiently achieved in the low frequency band, although it is lower than in the case of normal incidence. This is because the sound pressure on the panel is almost uniform at a low frequency where the wavelength of the sound is longer than the panel size, even when obliquely incident. Because.

  A problem in the case of oblique incidence is that the control effect is reduced in the vicinity of the natural frequency of the cancellation type vibration mode. This is because in the present invention, since the actuator is arranged to suppress the primary radiation mode, the radiation mode by the vibration mode (cancellation type vibration mode) other than the non-cancellation type vibration mode cannot be controlled. is there.

  In order to improve this problem, we devised a method to improve the vibration control of the panel. FIG. 23 shows the relationship between the frequency of sound incident on the panel at an incident angle of 30 ° and the sound transmission loss when the panel loss coefficient η is changed to 0.01, 0.05, 0.1, 0.2, 0.5. It is a graph.

  Referring to FIG. 23, it can be seen that the drop in the control effect near the natural frequency of the cancellation type vibration mode is improved by increasing the panel loss coefficient η to improve the panel damping performance. Since the cancellation type vibration mode has low radiation efficiency, it affects the transmitted sound only near the natural frequency. Therefore, by suppressing the resonance of these vibration modes, it is possible to improve the problem that the control effect decreases in the vicinity of the natural frequency of the cancellation type vibration mode in the case of oblique incidence.

  Further, from the result of FIG. 23, it is considered that the panel loss coefficient η is preferably 0.05 or more in order to obtain a control effect in a wide frequency band in the case of oblique incidence.

  In addition, in order to improve the damping performance of the panel, the panel itself is made of a highly damping material, the damping material is attached to the panel, and the laminated structure is sandwiched between two panels. For example, measures can be taken such as absorbing vibrations at the support, or using active vibration control to improve vibration suppression using a vibration pickup or actuator on the panel.

5 Verification of sound insulation performance by experiment Subsequently, the sound insulation performance of the active sound insulation device and the active sound insulation method of the present invention was verified by experiments. In the following, conditions such as panel dimensions and materials, actuator type, control algorithm of control means, etc. are the same as those adopted in “2 Specific Embodiment of Active Sound Insulation Device of the Present Invention” unless otherwise specified. is there.

  FIG. 24 is a diagram showing an outline of experimental equipment used in the experiment. In this experiment, as shown in FIG. 24, the room on the sound source side and the room on the sound receiving side were separated by a panel. As the panel, a multilayer board in which a vibration damping material having a thickness of 1 mm was attached to an aluminum plate whose specifications are shown in Table 1 above was used. The panel was simply supported by sandwiching the periphery with a knife edge. An actuator was attached to a predetermined part of the panel. A voice coil type point actuator was used as the actuator. The arrangement of the actuator is the same as the arrangement C in FIG.

  In the room on the sound source side, a speaker as a sound source was arranged. Four speakers were placed on the wall facing the panel. The distance from the panel to the speaker is 2.0m. A sound-absorbing wedge with a thickness of 500 mm was attached to each wall of the room on the sound source side so that the sound was incident perpendicular to the panel.

On the other hand, the received sound side room, and a sensor for detecting the sound transmitted through the panel, and sound power measuring means for measuring the sound power W ₀ and transmission acoustic power W _T will be described later, sound power measuring means And a supporting means for supporting the movably. A microphone was used as the sensor. This sensor was installed 2.5m from the panel. An intensity probe was used as the sound power measuring means. Measurement of acoustic power W ₀ and transmission acoustic power W _T was performed in 1/12 octave band. The receiving room was an anechoic room.

  Furthermore, the sound source, the actuator, and the sensor were connected to control means arranged outside. As a control means, a digital signal processing device comprising a DSP board, a D / A board, and an A / D board was used. The sampling frequency of the control means is 3 kHz, and the number of taps is 1000. The control algorithm of the control means is “Filtered-X LMS algorithm”, and adaptive control is performed so that the sound pressure at the position where the microphone is installed is minimized. In the experiment, white noise of 1.6 kHz or less was used.

Furthermore, as an index for evaluating the sound insulation performance, the insertion loss IL [dB] defined by the following formula 38 is adopted instead of the sound transmission loss R [dB] defined by the above formula 21. This is because it is difficult to experimentally determine the incident sound power, and it is difficult to measure the sound transmission loss R [dB] at the time of normal incidence.

The experiment was conducted according to the following procedure using the above experimental equipment.
[1] Measure the acoustic power W ₀ that reaches the sound receiving side from the sound source side without the panel attached.
[2] partition the source side and the sound receiving side panel arranged actuator, measuring the transmission sound power W _T coming transmitted to the sound receiving side.
[3] The insertion loss IL [dB] is obtained by the above equation 38.

  FIG. 25 is a graph showing the relationship between the sound frequency and the insertion loss IL [dB] at the time of control and the insertion loss IL [dB] at the time of non-control measured using the experimental equipment of FIG. As can be seen from FIG. 25, in this experiment, an excellent result as obtained by calculation is not obtained. This is considered to be due to the low sound insulation performance around the panel in the experiment. However, it is still understood that the insertion loss IL [dB] is improved by 10 dB or more in a wide range of the low frequency band at the time of control. From the above, it was proved by experiments that the active sound insulation device and the active sound insulation method of the present invention exhibit excellent sound insulation performance.

It is the figure which showed an example of the active sound insulation control currently performed. It is the figure which showed the calculation model of active sound insulation control. It is the figure which showed the shape of the radiation mode from the 1st order to the 3rd order in 100Hz. It is the graph which showed the relationship between the frequency of sound, and the sound transmission loss at the time of non-control. It is the graph which showed the relationship between the frequency of sound, the acoustic power of the radiation mode from the 1st order to the 3rd order at the time of non-control, and the acoustic power of all the transmitted sound. It is the figure which showed the vibration distribution when a panel is vibrated with 159.5Hz and 277.5Hz which are the antiresonance frequencies. It is the graph which showed the relationship between the frequency of sound, the sound transmission loss when the periphery of a panel is simply supported, and the sound transmission loss when the periphery of a panel is fixedly supported. It is the figure which showed an example of the shape which can be employ | adopted as a panel. 9 is a graph showing the relationship between sound frequency and sound transmission loss R [dB] during non-control when the panel having the shape shown in FIG. 8 is used. It is the figure which showed the specific embodiment of the active sound-insulation apparatus of this invention. FIG. 11 is a diagram for explaining the arrangement of actuators in the active sound insulation device shown in FIG. Sound frequency, sound transmission loss when the sound is vertically incident on the panel with the actuators arranged in the arrangements A to C in FIG. 11, and the sound is vertically incident on the non-control panel. It is the graph which showed the relationship with the sound transmission loss in a case. It is the figure which showed arrangement | positioning of the actuator with respect to a panel. Sound frequency, sound transmission loss when the sound is vertically incident on the panel with the actuator arranged in FIG. 13, and sound when the sound is vertically incident on the panel when not controlled It is the graph which showed the relationship with transmission loss. The frequency of sound, the mean square speed of the panel when the sound is vertically incident on the panel with the actuator arranged in Fig. 13, and the sound is vertically incident on the panel when not controlled It is the graph which showed the square mean speed of the panel in. Sound frequency, radiation efficiency when sound is vertically incident on a panel with actuators arranged in arrangements C to G in Fig. 13, and when sound is vertically incident on a panel when not controlled It is the graph which showed the relationship with the radiation efficiency of. It is the graph which showed the relationship between the sound transmission loss at the time of non-control at the time of changing the thickness of a panel with the thickness of 1mm, 2mm, 3mm, and 5mm. It is the graph which showed the relationship between the sound transmission loss at the time of control when changing the sound frequency and the thickness of the panel to 1 mm, 2 mm, 3 mm and 5 mm. It is the graph which showed the relationship between the sound transmission loss at the time of non-control at the time of changing the thickness of a large-sized panel with 1 mm, 2 mm, 3 mm, and 5 mm. 6 is a graph showing the relationship between sound frequency and sound transmission loss during control when the thickness of a large panel is changed to 1 mm, 2 mm, 3 mm, and 5 mm. It is the figure which showed the state which divided | segmented the panel into several small panels and has arrange | positioned the actuator to each small panel. Sound transmission loss during control when the sound frequency and the sound incident angle on the panel are changed to 0 ° (vertical incidence), 15 °, 30 °, 60 °, and when the sound is vertically incident on the panel It is the graph which showed the relationship with the sound transmission loss at the time of non-control. 6 is a graph showing the relationship between the frequency of sound incident on a panel at an incident angle of 30 ° and the sound transmission loss when the panel loss coefficient η is changed to 0.01, 0.05, 0.1, 0.2, and 0.5. It is the figure which showed the outline | summary of the experimental equipment used for experiment. 25 is a graph showing the relationship between the sound frequency and the insertion loss IL [dB] during control and the insertion loss IL [dB] during non-control measured using the experimental equipment of FIG. It is the figure which showed the example which applied the active sound insulation apparatus and active sound insulation method of this invention to the soundproof box. It is the figure which showed the example which applied the active sound insulation apparatus and active sound insulation method of this invention to the wall which partitions off the room in a building. It is the figure which showed the example which applied the active sound insulation apparatus and active sound insulation method of this invention to the outer wall in a building. It is the figure which showed the example which applied the active sound-insulation apparatus and active sound-insulation method of this invention to the aircraft.

Claims (8)

A panel for separating the sound source side and the sound receiving side, a sensor for detecting sound emitted from the sound source or vibration of the panel, control means for generating a control signal in accordance with the sound or vibration detected by the sensor, and control An active sound insulation device including an actuator that suppresses sound transmitted through the panel by exciting a predetermined portion of the panel based on a control signal emitted by the means,
Actuator is disposed on at least one point on the nodal lines planned line L _a in the panel as a nodal lines in the sound with respect to the panel in the non-control was anti-resonance in vertically incident allowed by the anti-resonance frequency omega _a by An active sound insulation device characterized by comprising: Among the points on the nodal lines planned line L _a, active sound insulation device according to claim 1, wherein the actuator that overlaps the nodal lines of the low-order cancellation vibration mode is provided. Panel has a point-symmetrical shape or line symmetry shape, among the points on the nodal lines planned line L _a, at least with respect to a straight line passing through the point-symmetrical or said center relative to the center of the panel in a line symmetrical positions 2 2. The active sound insulation device according to claim 1, wherein an actuator is disposed at the point. A joint line will line L _a in the panel as a nodal lines in the sound with respect to the panel in the non-control was anti-resonance in vertically incident allowed by the anti-resonance frequency omega _a, the sound to the panel at the time of non-control The actuator is arranged at at least one of the intersections with the nodal line L _b in the panel that becomes the nodal line when the beam is vertically incident and anti-resonant at the antiresonance frequency ω _b (> ω _a ) 2. The active sound insulation device according to claim 1.   2. The active sound insulation device according to claim 1, wherein the panel has a loss coefficient of 0.05 or more. Panel is divided into a plurality of small panels, each of the active sound insulation device according to claim 1, wherein the actuator is arranged on at least one point on the nodal lines planned line L _a in the small panel. An active sound insulation panel with an actuator that suppresses sound transmitted through the panel by vibrating the panel at a predetermined position of the panel for separating the sound source side and the sound receiving side,
Actuator is disposed on at least one point on the nodal lines planned line L _a in the panel as a nodal lines in the sound with respect to the panel in the non-control was anti-resonance in vertically incident allowed by the anti-resonance frequency omega _a by An active sound insulation panel. A panel for separating the sound source side and the sound receiving side, a sensor for detecting sound emitted from the sound source or vibration of the panel, control means for generating a control signal in accordance with the sound or vibration detected by the sensor, and control An active sound insulation method that suppresses sound transmitted through the panel using an actuator that vibrates a predetermined portion of the panel based on a control signal emitted by the means,
Placing the actuator in at least one point on the nodal lines planned line L _a in the panel as a nodal lines when obtained by the anti-resonance is incident perpendicularly sounds to the panel at the time of non-control by the anti-resonance frequency omega _a An active sound insulation method characterized by the above.