JPH11160145A - Acoustic evaluating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evaluate the sound of an object structure during its actual operation when its structure is changed with the vibration data during its actual operation without actually forming the structure. SOLUTION: This acoustic evaluating system is provided with a vibration measuring means 2 measuring the vibration state during the actual operation of an object structure, a modal parameter calculating means 4 calculating the modal parameters of the object structure, a virtual exciting force calculating means 6 calculating the virtual exciting force vibrating the object structure nearly in the same way as the vibration state during the actual operation based on the modal parameters of the object structure calculated by the modal parameter calculating means 4 and the vibration data during the actual operation measured by the vibration measuring means 2, and an acoustic radiation power calculating means 8 calculating the acoustic radiation power when the structure of the object structure is changed with the virtual exciting force calculated by the virtual exciting force calculating means 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic evaluation system, and more particularly to an acoustic evaluation system for calculating acoustic radiation power when the shape of a mechanical structure is changed.

[0002]

2. Description of the Related Art The noise of a mechanical structure is closely related to its vibration, but there are few techniques for clarifying the relationship between vibration and noise.

[0003]

In particular, when the exciting force actually applied to the mechanical structure is unknown, how the noise changes by changing the shape of the mechanical structure. I couldn't know.

[0004]

The object of the present invention is to solve the disadvantages of the prior art and, in particular, to provide vibration data during the actual operation of the target structure,
To provide an acoustic evaluation system capable of calculating a virtual excitation force equal to an actual excitation force that vibrates a target structure during the actual operation from a modal parameter of the target structure. And its purpose. It is another object of the present invention to provide an acoustic evaluation system capable of obtaining acoustic radiation power when the structure of a target structure is changed using a virtual excitation force. The present invention can also evaluate the sound of the actual operation when the structure of the target structure is changed using the vibration data during the actual operation without actually creating the structure. It is an object of the present invention to provide a sound evaluation system that can perform the evaluation. Another object of the present invention is to provide an acoustic evaluation system capable of calculating the optimization of a structure for reducing the sound of a structure to be actually operated under a specific condition, for example, a specific frequency.

[0005]

Therefore, according to the present invention, there is provided a vibration measuring means for measuring a vibration state of a target structure during actual operation, a modal parameter calculating means for calculating a modal parameter of the target structure, and the modal parameter calculating means. Based on the modal parameters of the target structure calculated by the parameter calculating means and the vibration data during the actual operation measured by the vibration measuring means, the virtual structure vibrates the target structure substantially in the same manner as the vibration state during the actual operation. Virtual excitation force calculation means for calculating the vibration force, and sound for calculating acoustic radiation power when the structure of the target structure is changed using the virtual excitation force calculated by the virtual excitation force calculation means Radiation power calculation means.

[0006] The modal parameter of the target structure is data representing the vibration characteristics of the shape obtained by an experimental modal analysis or FEM analysis with respect to the shape / structure of the target structure to be actually operated. Therefore, before or after actual operation, the shape of the actually operated target structure needs to be known. Vibration data during actual operation refers to, for example, the state of vibration of the target structure during actual operation, such as data obtained by measuring the displacement of a plurality of measurement points of the target structure that is actually operating in time series. Data refers to data necessary for calculating the frequency, displacement, and resonance frequency (natural frequency). For this measurement, an acceleration pickup may be attached to each measurement point to measure the acceleration of the measurement point, or a laser vibration meter may be used to measure the displacement of the measurement point in a non-contact manner. Is also good. The virtual excitation force is an excitation force obtained by the same calculation as the excitation force given during actual operation. That is, in many cases, the exciting force during actual operation cannot be measured. On the other hand, the excitation force can be estimated from the modal parameters of the target structure and the vibration data. Then, an excitation force is required for calculating the acoustic radiation power. For this reason, in the present invention, a virtual exciting force for causing the same vibration as the vibration of the target structure during actual operation is calculated from the modal parameters and the vibration data. The sound radiation power when the structure of the target structure is changed is determined by attaching a damping material to the target structure,
Alternatively, it is the radiation power of the sound generated when the changed shape model is actually operated when a part of the thickness is changed. That is, in the present invention, by changing the shape in the computer without actually creating a model with the changed shape, the characteristics of the sound emitted by the changed shape can be obtained by calculation. Since the sound radiation power at this time is obtained by the virtual excitation force,
The acoustic radiation power when the changed shape is actually operated is simulated. Since the sound radiation power of the changed shape model can be obtained based on the frequency axis, for example, by changing the shape in a computer, for example, a damping material is attached with the purpose of reducing sound at a certain frequency. Processing such as optimizing the position can be performed in a short time without actually manufacturing a structure.

[0007] For example, when optimizing the structure of a head cover in order to reduce the sound radiated from the head cover of a four-wheeled engine, it is necessary to reduce the sound that can be heard in the vehicle cabin or to minimize the sound pressure. It is necessary to reduce the acoustic radiation power at high frequencies. In this case, first, a modal parameter is obtained by modal analysis of the head cover. Next, a plurality of acceleration pickups are attached to the engine head cover, and the four-wheeled vehicle is actually driven to measure vibration data of the engine head cover. Next, the exciting force applied to the head cover in the actual operation is calculated from the modal parameters of the head cover of the engine and the vibration data during the actual operation. The sound radiation power is measured by changing the shape of the engine head cover based on the virtual excitation force. At this time, for example, if it is known that a certain frequency sound can be heard well in the vehicle interior, that is, if the contribution ratio of the acoustic radiation power output from the head cover to the vehicle interior is known, the frequency to be reduced is determined. Is determined. The contribution rate is
It is obtained by comparing the sound radiation power of the head cover with the sound inside the vehicle. Then, a portion where the thickness of the head cover of the engine is changed is divided into blocks, and if there is a combination of shapes that best reduces acoustic radiation power of a frequency having a high contribution rate to the vehicle cabin among combinations of changes in the shape, Thus, it is possible to specify the shape of the engine block that reduces noise into the vehicle interior. That is, according to the present invention, such optimization of the structure can be performed by simulation in a computer.

In the present invention, the virtual excitation force calculating means calculates actual excitation force for each vibration mode of the target structure based on vibration data during actual operation, and virtual excitation force calculation means for each vibration mode. Means for calculating a virtual excitation force for each vibration mode based on the actual excitation force and the modal parameters,
Considering the superposition of the vibration modes, each mode of the vibration data is measured so that the difference between the measured value of the vibration speed in each mode at each measurement point and the calculated value of the vibration speed by the virtual excitation force is minimized. Means for optimizing the value of the virtual excitation force,
The configuration is adopted. This aims to achieve the above-mentioned object.

There are various methods for specifying the vibration mode.
Here, for a structure having relatively good mode separation, a peak point of a frequency transfer function calculated from vibration data during actual operation is set as a natural frequency, and a virtual excitation force is set for each natural frequency or vibration mode. Is calculated. Next, the value of the virtual excitation force for each mode is optimized in consideration of the overlap between the modes. According to this, it was confirmed that the acoustic radiation power during actual operation and the acoustic radiation power calculated based on the virtual excitation force were very similar, and that the acoustic radiation power could be determined by the virtual excitation force. .

[0010]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the acoustic evaluation system according to the present invention includes a vibration measurement unit 2 that measures a vibration state of a target structure during actual operation, a modal parameter calculation unit 4 that calculates a modal parameter of the target structure,
Based on the modal parameters of the target structure calculated by the modal parameter calculating means 4 and the vibration data during actual operation measured by the vibration measuring means 2, the target structure is substantially similar to the vibration state during actual operation. Virtual exciting force calculating means 6 for calculating a virtual exciting force to be vibrated, and acoustic radiation when the structure of the target structure is changed using the virtual exciting force calculated by the virtual exciting force calculating means And a sound radiation power calculating means 8 for calculating power.

As shown in FIG. 2, the virtual excitation force calculation means calculates vibration data (amplitude and phase of vibration) for each natural frequency of the target structure based on vibration data during actual operation. (S1), means (S2) for calculating a virtual exciting force for each vibration mode based on the actual exciting force and the modal parameter for each vibration mode, and vibration data in consideration of the superposition of the vibration modes. Means for optimizing the value of the virtual excitation force for each mode so as to minimize the difference between the actually measured value of the vibration speed in each mode at each measurement point and the calculated value of the vibration speed by the virtual excitation force (S3).
This makes it possible to calculate the exciting force that vibrates the target structure during actual operation.

In the example of optimizing a shape, as shown in FIG. 3, a shape model generating means (S1) for calculating a modal parameter by changing a shape model of a target structure.
1) and the acoustic radiation power for calculating the acoustic radiation power of the shape model based on the modal parameters of the shape model generated by the shape model generation means and the virtual excitation force calculated by the virtual excitation force calculation means. A calculating means (S12) and a shape optimizing means (S13) for selecting a shape model having an optimum sound based on the sound radiation power for each shape model calculated by the sound radiation power calculating means. As a result, it is possible to select a shape that optimizes the acoustic radiation power.

FIG. 4 is a block diagram showing the configuration of hardware resources according to the present embodiment. In the present embodiment, FIG.
In order to realize the functions shown in FIG. 3 to FIG. 3, a data recording device 10 that measures time-series vibration data when the target structure is actually operated at a plurality of measurement points of the target structure, and the data recording device 10 An arithmetic unit 12 that calculates a virtual excitation force that causes a vibration state when the target structure is actually operated based on the measured time-series vibration data;
A storage unit 14 for storing data calculated by the calculation device 12 and modal parameters of the initial shape model of the target structure. The arithmetic unit 12 is provided with an output device 16 for reproducing acoustic radiation data.

The arithmetic unit 12 converts the actual time-series vibration data into frequency components, extracts a natural frequency from the actual frequency data, and executes the actual operation for each natural frequency. Means for calculating the amplitude and phase of vibration, and for each natural frequency based on frequency vibration data of actual operation based on modal parameters of the initial shape model stored in the storage unit and vibration speeds of a plurality of measurement points of the target structure Means for calculating a virtual excitation force.

The arithmetic unit 12 further includes means for changing the shape of the initial shape model of the target structure, means for calculating a modal parameter of the shape change model, a modal parameter of the shape change model, and a virtual excitation force. Means for calculating the sound radiation power of the shape change model based on the above, and a shape change model having an optimum shape under the condition selected from predetermined sound conditions and sound radiation power for each of the plurality of shape change models. May be provided.

Various means of the arithmetic unit 12 are realized by a program for an acoustic evaluation system. This program has an instruction for causing the arithmetic unit to realize each of the above units. Here, the “command to be performed” includes a command to be realized depending on the operating system and hardware resources of the arithmetic device. For example, if the operating system performs the process of displaying data on the display,
The sound evaluation system program has a command to request the operating system to display. of course,
The sound evaluation system program may realize all controls including input / output of the arithmetic unit 12 and file management.

More specifically, the arithmetic unit determines in advance modal parameters of the vibration of the target structure before and after the structural change. That is, the arithmetic unit performs an experimental mode analysis, an FEM mode analysis, and a mode synthesis method. These calculation results are stored in the storage device. Next, the data collection device collects time-series data of the vibration speed at a plurality of points of the structure. Based on the vibration data, the arithmetic device obtains amplitude and phase information for each frequency, and stores the information in the storage device.

Further, a virtual excitation force is calculated for each mode from the modal parameters of the target structure and the amplitude and phase information for each frequency based on the vibration data from the storage device. Further, the virtual excitation force is optimized. The arithmetic device stores the optimized virtual excitation force for each mode in the storage device. Then, the modal parameters and the virtual excitation force after the structure change are read from the storage device, and the acoustic radiation power is calculated. By preparing a plurality of models after the structural change, a plurality of acoustic radiation powers are calculated. To actually reproduce the acoustic radiation power, the acoustic radiation power is converted into time-series data and reproduced from the speaker of the output device.

If the optimization of the structure is defined in advance, a shape that best meets the condition is selected from a plurality of acoustic radiation powers of a plurality of structures. further,
The structure may be automatically changed under a certain condition. For example, the maximum value that can increase the thickness of the surface of an engine block, etc., and the minimum area (unit) that changes the thickness
May be determined in advance, and the number of changed shapes obtained by dividing the surface of the engine block in the minimum unit may be automatically generated.

The details of the sound evaluation method according to the present embodiment will be described. [Estimation of virtual excitation force] The virtual excitation force at the virtual excitation point is estimated from the vibration characteristics (modal parameters) of the mechanical structure and the vibration data during actual operation. The virtual excitation force is a virtual excitation force capable of expressing a vibration pattern during actual operation. This virtual excitation force is represented by one virtual excitation point if there is one vibration source. That is, even if vibrations are input to the mechanical structure (target structure) from multiple locations,
If the vibration source of the vibration is at one place, the vibration pattern can be expressed at one virtual excitation point. If there are a plurality of vibration sources, a number of virtual excitation points corresponding to the number are set.

The modal parameter is a quantity that expresses the vibration characteristic of a structure in a mode-separated manner, and includes a mode mass, a natural frequency, a mode damping ratio, and a mode vector.
The natural frequency refers to a frequency at which the structure resonates. The modal mass is an amount corresponding to each natural frequency, and when this value is small, it is easy to vibrate. The mode damping ratio is an amount corresponding to each natural frequency. If this value is small, the vibration does not easily converge. The mode vector is an amount corresponding to each natural frequency,
This is a quantity that expresses what kind of deformed shape the natural frequency has. This mode vector is not an absolute quantity, and is often normalized with, for example, a mode mass of 1.

The virtual exciting force is estimated by the following procedure. (1). The experimental mode analysis and the FEM analysis of the target structure are performed, and the above-described modal parameters are obtained. (2). The vibration of the target structure is measured during actual operation, and the magnitude and phase relationship of the vibration speed for each natural frequency are obtained. As signal processing, an auto spectrum and a cross spectrum are calculated. In the case of a structure with small attenuation, the phase is ± 90 degrees with respect to the excitation force. (3). From the single mode vibration velocity estimated value and the measured value,
The virtual excitation force for each mode is calculated. (4). Next, the virtual excitation force for each mode is updated to an optimal value in consideration of the mode overlap.

The estimation of the virtual exciting force will be described in detail.
The vibration velocity (acceleration) Vk at a certain point k at a certain frequency can be obtained by the following equation (1) from the property of mode superposition. Then, for example, when three points of vibration velocity are measured in three modes, Expression (2) is satisfied.

[0024]

(Equation 1)

Since this equation (2) is a ternary linear equation, a1, a2 and a3 can be determined. In the computer, the calculation is performed by multiplying the inverse matrix of the mode vector from the left side of both sides. When the number of points on the vibrometer is smaller than the number of modes, am can be obtained by calculating a pseudo inverse matrix of the mode matrix. On the other hand, when the number of vibration measurement points is larger than the number of modes, am can be obtained from the least squares approximation.

Here, when the influence of one mode is very large (when the mode separation is perfect) at the frequency of interest (natural frequency), the vibration speed at the natural frequency is given by the following equation (3). Can be represented by Then, the following equation (4) is obtained from the equations (1) and (3).

[0027]

(Equation 2)

From the above calculations, the virtual excitation force considering only the mode having the largest effect was determined for each vibration mode. Since the vibration can be expressed by the superposition of the vibrations in each vibration mode, next, the superposition of the modes is calculated, and the response speed of each measurement point of the target structure is calculated.

[0029]

(Equation 3)

[Optimization of Virtual Exciting Force] As shown in Expression (5), the response speed of vibration can be obtained by superimposing modes. On the other hand, Fm in Expression (5) is a virtual excitation force when considered in a single mode, and is not a virtual excitation force that can represent an actual vibration state. Therefore, the calculated value V
The excitation force Fm for each mode is optimized as a design variable so as to minimize the error between calk and the measured value Vrealk. For example, if there are 8 measurement points and 11 vibration modes, there is a virtual excitation force for each vibration mode, and there is a response speed at the measurement point for each vibration mode. For optimization, a calculated value V for a response speed of 88
Calk is compared with the actually measured value Vrealk to optimize 11 virtual excitation forces.

Optimization is a calculation method based on mathematical programming, and is generally formulated as follows. Objective F (x) Minimization Constraint g (x) ≦ 0 Design Variable x A combination of design variables that minimizes the objective is determined within a range satisfying the constraint. In the above-described problem of optimizing the virtual excitation force, the following formula (6) is used.

[0032]

(Equation 4)

With the virtual excitation force Fm for each mode described above as an initial value, Fm is updated so as to minimize the purpose (error between the calculated value and the actually measured value). The vibration during actual operation can be represented by the virtual excitation force obtained as a result. That is, for each of a plurality of modes at a plurality of measurement points, the virtual excitation force Fm for each mode is optimized for the purpose of making the difference between the calculated value and the measured value by the virtual excitation force close to “0”. I do.

[Estimation of Acoustic Radiation Power] Since the acoustic radiation power is estimated from the vibration state of the surface of the structure, it is possible to estimate the acoustic radiation power using the virtual excitation force.
That is, the acoustic radiation power can be calculated using the following amounts calculated from the above-described virtual excitation force and the modal parameters of the vibration of the mechanical structure. Total loss coefficient: Total energy consumed from a vibrating structure Radiation loss coefficient: Energy consumed as sound Driving point mobility: Transfer function of force and velocity at an excitation point, and the structure is easy to vibrate A quantity representing the

[0035]

(Equation 5)

The vibration parameters of the initial model are obtained in advance by experimental mode analysis or FEM mode analysis. The vibration parameters after the structural change are obtained in advance by FEM mode analysis or mode synthesis. In the mode synthesis method, the physical degrees of freedom of vibration are coordinate-transformed into degrees of freedom of the mode,
This is a method of performing vibration analysis with a reduced number of degrees of freedom. When the virtual excitation force is obtained from the vibration data during actual operation, the frequency characteristics of the acoustic radiation power before and after the structural change can be easily calculated. Regarding such a method of calculating the acoustic radiation power, see the Transactions of the Japan Society of Mechanical Engineers (C-Polarization), vol.
990-11), a study on estimation of radiated power of gear noise, disclosed by Iwao Hayashi et al.

FIG. 5 shows an example in which a flat plate is used as a target structure. Vibration is measured at eight vibration measurement points 22 by applying a vibration force to an actual vibration point 21. The virtual excitation point 23 of the virtual excitation force is an end as shown in the figure. The solid line in FIG. 6 is a graph showing the acoustic radiation power for each frequency when the actual excitation point shown in FIG. 5 is excited at 1N. A virtual excitation force is obtained from time-series data (vibration data) of acceleration or displacement at each measurement point measured at each vibration measurement point shown in FIG. 5 and a modal matrix of the plate, and then, based on the virtual excitation force An example in which the acoustic radiation power is calculated by using the dotted line is shown.
Both agree well, confirming that it is possible to estimate the acoustic radiation power using the virtual excitation force.

[Optimization of Structure Shape] Next, optimization of the structure shape will be described. First, when the target structure shown in FIG. 7 was excited, the experimental value of the acoustic radiation power was the value shown by the dotted line in FIG. An estimated value calculated using the virtual excitation force is shown by a solid line in FIG. In the example shown in FIG.
300Hz, 500H in frequency band up to Hz
Since the acoustic radiation power at z, 700 Hz is greater than the acoustic power at other frequencies, it is an object to reduce the acoustic radiation power in these three modes.

First, in order to reduce the acoustic radiation in the above three modes by changing the plate thickness, the portion where the plate thickness is increased or decreased was optimized. As a result of the optimization, FIG.
As shown in FIG. 5, the shape was formed to have a portion 30 having a reduced thickness and a portion 32 having a large thickness. FIG. 10 is a diagram showing the acoustic radiation power (dotted line) obtained by actual operation of the initial model and the acoustic radiation power (solid line) obtained by actual operation of the structure change model. As shown in FIG. 10, the sound power after the change of the thickness is 3
It is greatly reduced at 00 Hz, 500 Hz, and 700 Hz. The sound radiation power of the actual operation of the structure-change model substantially matches the estimated value of the sound radiation power of the virtual excitation force shown in FIG. Therefore, according to the present embodiment, the acoustic radiation power of the structure change model can be obtained in advance and by calculation without actually producing the structure change model shown in FIG.

Next, the change in the acoustic radiation power due to the attachment of the damping material will be examined. FIG. 12 is a diagram showing the result of optimizing the damping material attachment according to the present embodiment,
FIG. 13 shows an estimated value based on the virtual excitation force. According to the virtual excitation force, the sound around 700 Hz is greatly reduced. For this, the acoustic radiation power in actual operation was actually measured by attaching the damping material. As shown in FIG. 14, it was confirmed that the sound around 700 Hz was significantly reduced when the vibration damping material was actually attached to the location.

As described above, according to this embodiment, even when the exciting force is unknown, the exciting force can be estimated from the vibration data during actual operation, and the acoustic radiation power can be calculated. In addition, a change in sound quality due to a structural change of a structure can be confirmed in real time. Therefore, noise countermeasures can be taken in a short time.

[0042]

Since the present invention is constructed and functions as described above, according to this, a virtual exciting force is estimated from vibration data during actual operation, and the virtual exciting force after the structural change is used using the virtual exciting force. In order to obtain the sound radiation power, the sound radiation power after the change can be obtained without actually manufacturing a structure whose structure has been changed. The process of selecting from the change proposals can be automatically performed. Furthermore, since the virtual excitation force is optimized in consideration of the superposition of modes, it is possible to calculate an estimated value of the acoustic radiation power close to the actual acoustic radiation power. It is possible to provide an excellent sound quality evaluation system which can evaluate sound and optimize the structure, which has not been achieved before.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing details of processing of a virtual excitation force calculating unit shown in FIG.

FIG. 3 is a flowchart illustrating a processing example when optimizing the shape of a target structure.

FIG. 4 is a block diagram showing a configuration of hardware resources of the acoustic evaluation system shown in FIG.

FIG. 5 is an explanatory diagram illustrating an example of a target structure according to the present embodiment.

6 is a graph showing sound radiation power due to actual operation of the structure shown in FIG. 5 and sound radiation power due to a virtual excitation force.

FIG. 7 is a perspective view showing an example of an analysis target model for changing a structure.

FIG. 8 is a graph showing an acoustic radiation power by an experiment of the structure shown in FIG. 7 and an estimated value of the acoustic radiation power by a virtual excitation force.

9 is an explanatory diagram illustrating a structural change by adding reinforcement of the structure shown in FIG. 7;

FIG. 10 is a graph showing a change in acoustic radiation power by actual measurement after the structure change shown in FIG. 9;

11 is a graph showing an estimated value of acoustic radiation power based on the virtual excitation force after the structure change shown in FIG. 9;

FIG. 12 is an explanatory view illustrating a structural change of the structure shown in FIG. 7 by attaching a damping material.

FIG. 13 is a graph showing an estimated value of acoustic radiation power based on a virtual excitation force after the damping material shown in FIG. 12 is attached.

14 is a graph showing acoustic radiation power by actual measurement after the damping material shown in FIG. 12 is attached.

[Explanation of symbols]

 2 Vibration measuring means 4 Modal parameter calculating means 6 Virtual excitation force calculating means 8 Sound radiation power calculating means 10 Data collecting device 12 Computing device 14 Storage device 16 Output device

Claims (5)

[Claims] 1. A vibration measuring means for measuring a vibration state of a target structure during actual operation, a modal parameter calculating means for calculating a modal parameter of the target structure, and the object calculated by the modal parameter calculating means. Based on the modal parameters of the structure and the vibration data during the actual operation measured by the vibration measuring means, a virtual excitation force for vibrating the target structure in substantially the same manner as the vibration state during the actual operation is calculated. Virtual excitation force calculation means,
Sound excitation power calculation means for calculating sound emission power when the structure of the target structure is changed using the virtual excitation force calculated by the virtual excitation force calculation means, A force calculating means for calculating a virtual exciting force for each vibration mode based on the vibration data and the modal parameter, and a measuring point of each of the vibration data in consideration of the superposition of the vibration modes. Means for optimizing the value of the virtual excitation force for each mode so as to minimize the difference between the actually measured value of the vibration velocity in the mode and the calculated value of the vibration velocity by the virtual excitation force. An acoustic evaluation system characterized by the following. 2. A vibration measuring means for measuring a vibration state of the target structure during actual operation, a modal parameter calculating means for calculating a modal parameter of the target structure, and the object calculated by the modal parameter calculating means. Based on the modal parameters of the structure and the vibration data during the actual operation measured by the vibration measuring means, a virtual excitation force for vibrating the target structure in substantially the same manner as the vibration state during the actual operation is calculated. A virtual excitation force calculating unit, and a shape model generating unit that calculates a modal parameter by changing a shape model of the target structure; a modal parameter of the shape model generated by the shape model generating unit; The acoustic radiation power of the shape model based on the virtual excitation force calculated by the excitation force calculation means A sound radiation power calculating means for calculating; and a shape optimizing means for selecting a shape model that provides an optimum sound based on the sound radiation power for each of the shape models calculated by the sound radiation power calculating means. An acoustic evaluation system characterized by the following. 3. A data recording device for measuring time-series vibration data when the target structure is actually operated at a plurality of measurement points of the target structure, and based on the time-series vibration data measured by the data recording device. An arithmetic unit for calculating a virtual excitation force that results in a vibration state when the target structure is actually operated, and storage for storing data calculated by the arithmetic unit and modal parameters of an initial shape model of the target structure. A means for converting the time series vibration data of the actual operation into frequency components, a means for extracting a natural frequency from the frequency vibration data of the actual operation, and stored in the storage unit. Based on the modal parameters of the initial shape model and the vibration velocities of the plurality of measurement points of the target structure, a fixed Acoustic evaluation system comprising the means for calculating a virtual excitation force for each frequency. 4. The arithmetic unit further includes means for changing the shape of the initial shape model of the target structure, means for calculating a modal parameter of the shape change model, modal parameters of the shape change model and the virtual A means for calculating the sound radiation power of the shape change model based on the excitation force, and a predetermined sound condition and the sound radiation power of each of the plurality of shape change models provide an optimum shape under the condition. 4. The acoustic evaluation system according to claim 3, further comprising means for selecting a shape change model. 5. A storage medium storing a program for an acoustic evaluation system, the program for an acoustic evaluation system comprising: a command to convert time-series vibration data of a target structure during actual operation into frequency components; A command to extract the natural frequency from the operating frequency vibration data and calculate the actual operating excitation force for each of the natural frequencies, a modal parameter of the initial shape model of the target structure, and a plurality of the target structures. A command for calculating a virtual excitation force for each natural frequency based on the frequency vibration data in actual operation based on the vibration speed of the measurement point, and generating a changed shape model by variously changing the shape of the initial shape model And a command to calculate the acoustic radiation power from the modal parameters of the deformed shape model and the virtual excitation force for each of the natural frequencies. Storage medium storing an acoustic evaluation program for the system, characterized in that it comprises a command and for selecting the deformed shape which is optimal acoustic radiation power on the basis of the acoustic radiation power of each deformed shape.