JPH07210174A - Active noise insulating method - Google Patents

Abstract

PURPOSE:To improve the noise insulation of a wall partitioning between a noise source room and a sound receiving room without using a weight wall or honeycomb structure wall. CONSTITUTION:The vibration mode of the wall 1 partitioning between the noise source room A and the sound receiving room B is analyzed to specify a vibration mode relating to the radiation of sound, a low-dimensional model for the wall 1 in the vibration mode is prepared, sensors 12c, 12u, 12l for detecting the acceleration/displacement of vibration are arranged on respective points of the wall 1 which correspond to respective mass points of the obtained low-dimensional model, and an actuator for applying braking force to the wall 1 is fixed at least to one position of the wall 1 and driven so as to suppress the vibration of the wall 1 based upon detection signals outputted from the sensors 12c, 12u, 12l. Consequently the vibration of the wall 1 can be controlled so as to cancel only vibration relating to the radiation of sound without exciting the vibration of a vibration mode unrelated to the radiation of sound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active sound insulation method in which the sound insulation is enhanced by controlling the vibration of the wall in consideration of the vibration characteristics of the wall separating the noise source room and the sound receiving room. is there.

[0002]

2. Description of the Related Art As a measure against noise, a method of canceling a sound emitted from a noise source in the air and a method of interrupting a sound propagation path on the way are considered. Regarding the former, noise control technology using so-called active canceller has emerged, in which sound from a noise source is detected by a microphone and a signal with the opposite phase and same amplitude is generated by a speaker to cancel the sound near the noise detection point (cancellation). However, it has been successfully applied to reduce noise in ducts, refrigerators, and company interiors of passenger cars. Regarding the latter, a passive method of shielding noise by partitioning a noise source chamber containing a noise source and a sound receiving chamber for which noise reduction is desired with a wall having a large sound transmission loss is still adopted.

[0003]

However, in order to obtain high sound insulation by the conventional sound insulation method, a material having a large specific gravity such as lead or iron is used for the wall, or a thick sound absorbing material such as a honeycomb structure is used. Must be used, and it is difficult to apply under conditions where weight reduction is required and volume is limited as in modern buildings.

The present invention was created under such circumstances, and an object thereof is to provide an active sound insulation method capable of obtaining high sound insulation without using a heavy wall or a honeycomb structure wall. Especially.

[0005]

In order to achieve the above object, in the active sound insulation method of the present invention, the vibration mode of the wall separating the noise source room and the sound receiving room is analyzed and involved in sound emission. A vibration mode is specified, a wall dimension reduction model is created in that vibration mode, and a sensor for detecting vibration acceleration or velocity is arranged at each point on the wall corresponding to each mass point of the obtained reduction model. At the same time, an actuator for applying a damping force to the wall is attached to at least one location on the wall, and the actuator is driven to suppress the vibration of the wall based on the detection signal from each sensor.

In the sound insulation method of the present invention, it is desirable to specify, as the vibration mode related to the radiation of the sound, a mode whose vibration mode shape is acoustically asymmetric.

Further, in the sound insulation method of the present invention, it is desirable that the actuator is attached to a portion of the wall corresponding to the mass point of the reduced model.

[0008]

The active sound insulation method of the present invention focuses on the fact that sound leakage occurs due to the fact that the wall separating the noise source chamber and the sound receiving chamber resonates with the noise and vibrates. It is intended to control the vibration of the wall so as to cancel it only for the target. Modern control theory, which is effective for vibration control, cannot be used unless the model of the controlled object is specified. However, since the wall has the characteristic of a distributed constant with infinite degrees of freedom, it is necessary to create a model with finite degrees of freedom. Moreover, if the degree of freedom is large, the controller becomes large and a large number of sensors are required. Therefore, it is desirable to reduce the dimension of the model to the minimum necessary. Therefore, in the method of the present invention, first perform a vibration mode analysis of the wall, to identify the vibration mode involved in the radiation of sound from among the many vibration modes existing in a predetermined frequency range to be sound insulation,
A low-dimensional model of the wall in the vibration mode is created. By creating a low-dimensional model of the controlled object in this way, it becomes possible to design a control system by applying modern control theory. Then, by arranging a sensor for detecting vibration acceleration or displacement near each point on the wall corresponding to each mass point of the obtained reduced-dimensional model, that is, near the maximum amplitude point of the specified vibration mode, The vibration state of the object, that is, the wall can be observed, and the vibration of the wall can be effectively suppressed by driving the actuator based on the detection signal from each sensor.

FIG. 5 shows an example of vibration mode analysis of a flat plate forming a wall, and shows resonance frequencies of first to fifth orders and vibration mode shapes. Focusing on the symmetry of the vibration mode type, 2-4
Assuming that the following vibration mode shapes are acoustically symmetric, the first and fifth order vibration mode shapes are acoustically asymmetric, and in the acoustically symmetric mode, the amounts of sound emission and suction cancel each other, The vibrational modes that are of concern for sound emission are the acoustically asymmetrical modes, the first and fifth modes. In this way, by examining the symmetry of the vibration mode shape, the vibration mode involved in sound emission can be easily specified.

The maximum amplitude point of the vibration mode thus identified corresponds to a node of another vibration mode that is not involved in sound emission. Therefore, if an actuator is attached to this point, the vibration of the wall is controlled so as to cancel only the vibration related to the sound emission without exciting the vibration of the vibration mode not related to the sound emission. be able to. That is, the active sound insulation method of the present invention is
By using the fact that it is impossible to control if an actuator is attached to the node of the vibration mode, and it becomes unobservable if the sensor is attached, the sensor or actuator is placed in the node of the mode you want to ignore and the vibration of the wall is controlled. According to this method, a control system that can structurally prevent spillover can be constructed.

[0011]

EXAMPLES Next, examples of the active sound insulation method of the present invention will be described.

FIG. 1 shows an example in which the active sound insulation method of the present invention is applied to a wall 1 which partitions a noise source room (piano room) A and a sound receiving room (study room) B. Noise source room A
Noise is transmitted to the sound receiving chamber B through the wall 1, the vibration sensors 12c, 12u, 12 mounted on the wall 1
If the actuator 4 is driven based on the signal from 1 to effectively suppress the vibration of the wall 1, the noise level of the sound receiving chamber B is significantly reduced.

FIG. 2 illustrates two configurations of apparatus configurations that may be employed to actively control wall vibration with the technique of the present invention. In the same figure (a), the actuator 4 is supported on a fixed surface and attached to the wall 1, and the sensors 12c, 12u, 12
This is a system in which the actuator 4 is controlled by a control amount generated by the controller 19 based on the detection signal of 1 to exert a damping force on the wall 1. In FIG. Mounted on the wall 1 via a support spring 20) and the actuator 4 instead of the fixed surface
This is a system in which the damping force of the actuator 4 is applied to the wall 1 by using the inertial force of the auxiliary mass md provided on the wall as a reaction force. In addition,
In the same figure (a), when the fixed surface cannot be obtained, the actuator 4 is supported by a separate supporting member. In that case,
It is desirable to design the controller 19 considering the characteristics of the support structure.

Next, in order to show the effectiveness of the active sound insulation method of the present invention, a case where this method is applied to a flat plate constituting a wall of a building will be shown by simulation and experiment.

The flat plate used in the experiment was 1200 × 1000 × 3 mm
It is a veneer board. As shown in FIG. 3, the flat plate 18 was held perpendicularly to the ground by fixing the periphery of the flat plate 18 to the support frame 3 fixed to the vertical wall 2. Then, as shown in FIG. 4, the flat plate 18 was decomposed into 120 finite elements, and an experimental mode analysis was performed. From this analysis result, it was found that there are first to seventh vibration modes in this plate between 0 Hz and 40 Hz. FIG. 5 shows the first to fifth cases in this case.
The following shows the resonance frequency and the vibration mode shape.As mentioned above, in the case of the acoustically symmetric vibration mode, assuming that the amounts of sound emission and suction cancel each other, the vibration mode in question here Are the first and fifth modes.

Next, based on the above consideration, based on the vibration mode shape of the flat plate 18 in the distributed constant system obtained by the experimental mode analysis, three mass points are designated at the positions on the flat plate 18 shown in FIG. Create a three-mass system model such as 4. Here, the mass of each mass point is m ₁ , m ₂ , m ₃ , the spring constant of the spring that connects each mass point is k _ij (i and j are the numbers of each mass point), and the spring constant of the spring between each mass point and the fixed surface is It is defined as k _i (i = 1, 2, 3). However, an external force f _i (i = 1, 2, 3) including a control force acts on each mass point. This 3
The equation of motion of the mass system model is as follows.

[0017]

[Equation 1]

When this equation is displayed in matrix,

[0019]

[Equation 2]

[0020] Therefore, the eigenmode matrix obtained by solving the eigenvalue problem of this equation is set as follows.

[0021]

[Equation 3]

On the other hand, the relationship between the inverse matrix of the mass matrix M in the physical coordinate system and the eigenmode matrix is

[0023]

[Equation 4]

From the property of the mass matrix without acceleration coupling,
A, B and C must be zero. Then the error function ε
Let us define ₁ and ε ₂ as follows, and consider bringing them closer to zero.

[0025]

[Equation 5]

Five variables φ11 and φ2 included in each expression
If the sensitivity matrices of 1, φ12, φ13, and φ23 are defined as in Expression (7) and the correction vector {δφ} is defined, the error function can be brought close to zero by Expression (8).

[0027]

[Equation 6]

The eigenmode matrix for diagonalizing the equation (6) is obtained by the equation (8), and the mass matrix is calculated as follows.

[0029]

[Equation 7]

Further, the stiffness matrix is calculated as follows.

[0031]

[Equation 8]

From these equations, the physical constants of the lumped-constant system three-degree-of-freedom model shown in FIG. 4 are obtained as follows.

[0033]

[Equation 9]

FIG. 7 shows a comparison between the vibration mode shape obtained by the actual experimental mode analysis and the vibration mode shape obtained by the present modeling method. In the figure, the thin solid line is the mode shape obtained by the experimental mode analysis, and the thick solid line is the mode shape obtained by this modeling method, and it can be seen that the modes match at three mass points.

With respect to the low-dimensional model created as described above, it is important to control the first-order vibration mode having the largest amplitude among the modes, and the actuator is attached to the central mass point (mass m ₂ ). Design the control system for the case. This central point corresponds to the nodes of the 2nd, 3rd, and 4th order vibration modes, and is therefore the point at which the vibrations of these modes are not excited. Also, this point corresponds to the center point of the actual flat plate 18.

The actuator 4 used in the active sound insulation method of the present invention is an improved speaker, and as shown in FIG. 9, a moving coil 6 wound around a movable core tube 5 and a ring surrounding the moving coil 6. The magnet 7 is provided, and the electromagnetic force is applied to the moving coil 6 by controlling the energization to the moving coil 6 to drive the diaphragm 8 attached to the movable core tube 3. The actuator 4 includes a support frame 2 for the flat plate 18 as shown in FIG.
A pair of support members 9 provided in parallel with each other
The flange portion 7a of the ring-shaped magnet 7 is fixed to the central portion of the flat plate 18 by fixing the flange portion 7a of the ring magnet 7 with the bolt 10, and the connection with the flat plate 18 is made by the tapered connector 11 protruding from the central portion of the diaphragm 8. This is done by connecting the tip portion to the central point of the flat plate 18 by a method such as adhesion. Note that FIG.
In the above, the supporting portion of the movable side element including the diaphragm 8 with respect to the fixed side element including the ring-shaped magnet 7 is a spring (spring constant k
_s) and the damping element (shown by modeling out the damping coefficient C _s).

Therefore, the actuator 4 is attached to the flat plate 18
FIG. 8 shows a reduced-dimensional physical model when attached to the. This physical model considers the support member 9 as a completely rigid body, and corresponds to the model in the case of FIG.

Using this physical model, the equation of motion when the actuator 4 is attached to the mass m ₂ is created, and this is represented by the equation of state as follows.

[0039]

[Equation 10]

When the control system is represented by the state equation in this way, the optimum control theory which is a modern control theory can be applied.
In the optimal control theory, the controlled variable is determined by the following state feedback.

[0041]

[Equation 11]

The vibration control of the flat plate 18 was simulated using the above design values. The result of the frequency response is shown in FIG. In the figure, (a) shows the frequency response at the center point of the flat plate 18, and (b) shows the frequency response of the flat plate 18.
The response at the point of the sensor attached to one antinode of the next vibration mode is shown. When active control is added as shown in (a), the peak of vibration in the first and fifth modes is reduced, and an effective sound insulation effect can be expected. Further, in (b), since the mounting position of the actuator 4 is at the center of the flat plate 18, the control cannot be performed for the secondary vibration mode, but from the result of this simulation, 2
1st and 5th without affecting the peak of next vibration mode
It can be seen that the peak of the next vibration mode can be reduced.

Next, FIG. 11 shows a time response corresponding to this frequency response. The time response at the center point of the plate 18 is
As shown in FIG. 7A, the active vibration control causes rapid convergence. Further, as shown in FIG. 2B, the time response at the upper point of the flat plate 18 has a second-order peak remaining as in the frequency response, but the first- and fifth-order modes are convergent.

Next, as shown in FIG. 3, for detecting the displacement of each point at the center point Pc of the flat plate 18 and the points Pu and Pl of the two antinodes (upper and lower sides) of the fifth-order vibration mode. The non-contact sensors 12c, 12u, and 12l were arranged, and the displacement data when the actuator 4 was operated and when the actuator 4 was not operated were measured.

The structure of the controller 19 used in this experiment is shown in FIG. In this configuration, the displacement signals from the non-contact sensors 12c, 12u, 12l are input to the personal computer 14 through the A / D converter 13 at a sampling frequency of 1 kHz. The personal computer 14 calculates the velocity signal by differentiating the displacement signal to obtain each state quantity. Then, the control quantity is calculated by multiplying the obtained state quantity by the feedback gain determined using the optimal control theory. Personal computer
The control amount calculated by the controller 14 is converted into an analog signal by the D / A converter 15, amplified by the amplifier 16, and input to the actuator 4. The actuator 4 is driven by this input signal to suppress the vibration of the flat plate 18.

FIG. 13 shows a frequency response obtained by an FFT analyzer when the upper part of the flat plate 18 is subjected to impulse excitation. In the figure, the dotted line is the response at the time of non-control, and the solid line is the response at the time of control. Further, (a) is the response detected by the sensor 12c attached to the central portion of the flat plate 18, and (b) is the flat plate 1
8 shows the response at the point of sensor 12u mounted on top of 8. When both are not controlled, peaks of the first and fifth frequencies are observed. When this flat plate 18 is controlled, 1
The peak values of the 5th and 5th orders are greatly reduced, indicating that the vibration is effectively controlled. Further, in FIG. 14B, since the actuator 4 is provided at the center point of the flat plate 18 which is the uncontrollable point of the secondary vibration mode,
The vibration of the second mode is observed without being excited. This agrees very well with the result of the simulation, which shows the effectiveness of the three-mass system model. Further, it is clear from this experimental result that the vibrations can be suppressed at the same time even in the higher-order modes of the 6th and 7th modes without causing spillover.

Therefore, by applying the configuration of the above control system to the wall 1 that separates the noise source room and the sound receiving room of an actual building, it is possible to prevent the vibration of the wall related to the radiation of the sound, and High sound insulation can be obtained without using a honeycomb structure wall or the like. When this method is applied to the actual wall 1, the personal computer 14 of the controller 19 shown in FIG. 12 can be replaced with a necessary minimum such as a microcomputer chip or a memory element.

In the above embodiment, if the control system is designed in consideration of the vibration of the support member 9 for supporting the actuator 4, the wall vibration can be controlled more effectively, and the sound insulation higher than that in the above embodiment can be obtained. It is possible to obtain sex. A physical model for designing this control system is created, for example, as shown in FIG. This physical model is obtained by adding the model element of the support member 9, that is, the lumped mass m _c of the support member 9 and the spring constant k _c between the model element of the actuator 4 and the fixed surface in the model shown in FIG. is there.

A motion equation is created using this physical model, and this is represented by the following equation of state. However, for simplicity, the damping element C _s of the actuator 4 is ignored.

[0050]

[Equation 12]

By applying the optimum control theory to this state equation to determine the control amount, the control system including the support member 9 of the actuator 4 can be designed. The control device in that case can use the same configuration as that in FIG. 12 by changing the programs and data stored in the computer 14.

The active sound insulation method of the present invention is not limited to the above embodiment, and for example, the mounting position of the actuator 4 can apply a damping force to a vibration mode related to sound emission. A flat plate 1 if it is possible and does not excite vibration modes that do not contribute to sound emission.
Other than the central portion of 8, the flat plate 18 may be attached to a plurality of places. When a plurality of actuators 4 are used, the control system becomes more complicated than that in the above example, but vibration control of the flat plate 18 having higher sound insulation is possible.

Further, the non-contact sensors 12c, 12u,
An acceleration sensor may be used instead of 12l. Since the acceleration sensor can be directly attached to the flat plate 18 for use, it does not erroneously detect the vibration of the support frame 3 as the vibration of the flat plate 18, and is more suitable for the actual control system than the non-contact sensor.

Further, the active sound insulation method of the present invention can be applied to iron plates, glass plates, and various other wall materials in addition to the veneer plate shown in the above example, and can also be effectively applied to walls of passenger cars and ships. it can.

In addition to the piano room shown in this embodiment, various examples such as various performance rooms and engine rooms can be considered as examples of the noise room. Further, if the wall is considered to be the outer wall of the hull, the characteristics of the ship recognized by the sound pattern can be arbitrarily changed by the active sound insulation method of the present invention.

[0056]

In summary, according to the active sound insulation method of the present invention, the following excellent effects can be exhibited.

(1) According to the first aspect of the present invention, the vibration mode of the wall that is involved in sound radiation is specified and the vibration of the wall is controlled so as to cancel it. It is possible to improve the sound insulation without using a wall having a large sound transmission loss.

(2) According to the second aspect of the invention, by examining the symmetry of the vibration mode shape, the vibration mode involved in sound emission can be easily specified.

(3) According to the third aspect of the present invention, the vibration of the vibration mode that does not contribute to the sound radiation is not excited, and only the vibration that is involved in the sound radiation is targeted so as to cancel it. Vibration can be controlled.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of an active sound insulation method of the present invention.

FIG. 2 is a schematic diagram showing a device configuration for implementing active sound insulation of the present invention.

FIG. 3 is a diagram showing an example of an experimental device for showing the effectiveness of the active sound insulation method of the present invention, (a) is a front view,
(B) is an AA 'sectional view of (a).

FIG. 4 is a conceptual diagram showing a structure of a flat plate forming a wall and a mass of a physical model thereof.

FIG. 5 is a diagram showing vibration modes of a flat plate obtained by experimental mode analysis.

FIG. 6 is a diagram showing a physical model (a reduced-dimensional model) of a flat plate.

FIG. 7 is a diagram showing a vibration mode shape of a flat plate and a reduced-dimensional model of the flat plate obtained by experiments and calculations.

FIG. 8 is a diagram showing a physical model when an actuator is attached.

FIG. 9 is a cross-sectional view showing the structure of an actuator.

FIG. 10 is a diagram showing a result of frequency response by simulation.

11 is a diagram showing a time response corresponding to the frequency response of FIG.

FIG. 12 is a configuration diagram of a controller used in the experiment.

FIG. 13 is a diagram showing a result of frequency response by simulation.

FIG. 14 is a diagram showing another example of a physical model when an actuator is attached.

[Explanation of symbols]

 1 wall 4 actuator 12c sensor 12u sensor 12l sensor A noise source room B sound receiving room

Claims (3)

[Claims] 1. A vibration mode of a wall separating a noise source room containing a noise source and a sound receiving room for which noise reduction is desired is analyzed to identify a vibration mode involved in sound emission, and the wall in the vibration mode is identified. A low-dimensional model is created, sensors for detecting vibration acceleration or displacement are arranged at each point on the wall corresponding to each mass point of the obtained low-dimensional model, and at least one place on the wall is controlled by the wall. An active sound insulation method characterized in that an actuator for applying a vibration force is attached, and the actuator is driven so as to suppress vibration of a wall based on a detection signal from each sensor. 2. The active sound insulation method according to claim 1, wherein a mode whose vibration mode shape is acoustically asymmetric is specified as a vibration mode related to radiation of the sound. 3. The active sound insulation method according to claim 1, wherein the actuator is attached to a portion of the wall corresponding to a mass point of the reduced model.