Calculation method and numerical calculation model data

Abstract

A calculation method according to the present invention comprises: a first step for disposing, in a virtual space, an equivalent mechanical element circuit that at least includes an electrical impedance equivalent mechanical element of a model in the virtual space, which is directly or indirectly connected to an action point where drive force generated in an electromechanical energy converter acts and which has properties that are mechanically equivalent to the electrical impedance Ze of the electromechanical energy converter; and a second step for setting, as a boundary condition, a disposition velocity equivalent to the drive voltage applied to the electromechanical energy converter, at one of end points of the equivalent mechanical element circuit or a joint that is indirectly connected to an end point and that serves as an end point.

Description

Calculation method and numerical calculation model data

[0001] The present disclosure relates to computational methods and numerical computational model data.

[0002] Patent Document 1 discloses a sound pressure characteristic calculation method that can accurately calculate the sound pressure characteristics of a speaker system without increasing the calculation scale or calculation time. The sound pressure characteristic calculation method includes a normalization step 1, a normalization step 2, a correction coefficient calculation step, and a sound pressure calculation step. In the normalization step 1, a relative vibration velocity difference, which is the velocity difference between the vibration velocity at the point of application where a driving force generated by an electromechanical energy converter acts and the vibration velocity at the point of reaction where a reaction force of the driving force acts, is normalized by the driving force to calculate normalized relative vibration velocity data. In the normalization step 2, normalized sound pressure data is calculated by normalizing the sound pressure at the sound pressure observation point by the driving force. In the correction coefficient calculation step, a driving force correction coefficient for determining the sound pressure at the sound pressure observation point is calculated from the normalized relative vibration velocity data, the electrical impedance value of the electromechanical energy converter, the force coefficient of the electromechanical energy converter, and a predetermined voltage. In the sound pressure calculation step, the sound pressure at the sound pressure observation point is calculated from the normalized sound pressure data and the driving force correction coefficient.

[0003] Non-Patent Document 1 discloses a method for analyzing the dynamic characteristics of a mechanical system expressed as a mechanical circuit by replacing it with an electric circuit.

[0004] Japanese Patent No. 7113168

[0005] Makoto Shimojo, "Symbolic Analysis of Mechanical Circuits, August 2010 Edition," [online], University of Electro-Communications, [accessed May 16, 2023], Internet <URL: http: / / www.rm.mce.uec.ac.jp / lecture / mech / MechCircuitMatrix.pdf>

[0006] Conventionally, a widely used method for calculating the reproduction sound pressure characteristics of a speaker system is to create a lumped parameter equivalent circuit in which the Thiele and Small parameters (hereinafter referred to as "TS") of the speaker unit and the acoustic structure or acoustic load of the housing are replaced with equivalent electric circuit components, and to calculate the sound pressure from a simulation of the circuit operation. Note that the object for which the sound pressure characteristics are calculated is not limited to a speaker system, but may also be an electromechanical system including an electric circuit and a mechanical element such as an actuator.

[0007] Furthermore, there is a method for calculating sound pressure characteristics by coupling acoustic vibration analysis using Finite Element Method (hereinafter referred to as "FEM") analysis (finite element method analysis) with a lumped parameter equivalent circuit using TS parameters, which is effective for calculating sound pressure when the acoustic structure of the housing in which the speaker unit is mounted is complex or when deformation vibration of the structure cannot be ignored.

[0008] In the sound pressure characteristic calculation method of Patent Document 1, when determining the sound pressure characteristics of a speaker system, a large-scale FEM model of a mechanical acoustic system without an electrical system model is first solved assuming a constant excitation force to calculate the mechanical impedance. The calculated mechanical impedance is then used to determine an excitation current value for constant voltage driving, and the sound pressure response to the excitation current value is calculated. However, this method requires two large-scale calculations, one for calculating the mechanical impedance and one for calculating the sound pressure response, which results in a long calculation time.

[0009] The present disclosure has been devised in view of the above-described conventional situation, and aims to reduce the calculation load of vibration characteristics and sound pressure characteristics of an electromechanical system.

[0010] The present disclosure provides a calculation method for calculating at least one of vibration and sound pressure generated in an electromechanical system of a speaker or actuator including an electromechanical energy converter having a stationary electrical impedance Ze when a drive voltage is applied to the electromechanical energy converter, the calculation method including: a first step of arranging in virtual space an equivalent mechanical element circuit that is directly or indirectly connected to a point of application at which a drive force generated in the electromechanical energy converter of a model in virtual space acts, and that includes at least a mechanical element having properties dynamically equivalent to the electrical impedance Ze of the electromechanical energy converter; and a second step of setting, as a boundary condition, a displacement velocity equivalent to the drive voltage applied to the electromechanical energy converter at any one of the endpoints of the equivalent mechanical element circuit or at a node that is indirectly connected to the endpoint and serves as an endpoint.

[0011] The present disclosure also provides numerical calculation model data that at least describes the above calculation method, which defines the positional relationship and connection conditions of the mechanical elements of the equivalent mechanical element circuit, the boundary conditions of the displacement velocity, and the elements to which the boundary conditions of the displacement velocity are set.

[0012] These comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0013] According to the present disclosure, it is possible to reduce the calculation load of the vibration characteristics and sound pressure characteristics of an electromechanical system.

[0014] FIG. 1 is a block diagram of components of a computing device according to the present embodiment; FIG. 2 is a diagram showing an example of a speaker system according to the present embodiment; FIG. 3 is a diagram showing an operation model of a speaker unit; Model diagram in which a circuit is replaced with an equivalent mechanical circuitDiagram showing an equivalent mechanical element circuit for calculating the sound pressure contribution of a speaker unitDiagram showing an equivalent mechanical element circuit for calculating the sound pressure contribution of a speaker unitDiagram showing a structural modelDiagram showing an internal acoustic spaceDiagram showing an external acoustic spaceDiagram showing a drive circuit of a two-way speaker including a network circuitDiagram in which a parallel-configured network circuit and a speaker unit electric circuit are replaced with an equivalent mechanical circuitDiagram showing an equivalent mechanical element circuit for calculating the sound pressure contribution of a tweeter unitDiagram showing an equivalent mechanical element circuit for calculating the sound pressure contribution of a speaker unitDiagram showing the definition of node namesDiagram showing an example of numerical calculation model dataDiagram showing an example of numerical calculation model dataDiagram showing the definition of node namesDiagram showing an example of numerical calculation model dataDiagram showing an example of numerical calculation model dataDiagram showing an example of numerical calculation model data

[0015] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the calculation method and numerical calculation model data according to the present disclosure will be described in detail. However, more detailed description than necessary may be omitted. For example, detailed descriptions of already well-known matters and redundant descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0016] 1 illustrates components of a computing device 100 according to this embodiment. FIG. 1 is a block diagram of the components of the computing device 100 according to this embodiment.

[0017] The computing device 100 is a device that calculates the sound pressure characteristics of a speaker system 30 (see FIG. 2). While a speaker will be used as an example, the system may be an electromechanical system including an electric circuit such as an actuator and a mechanical element. The speaker system 30 is an acoustic body that includes a sealed housing 32 placed in a free space and a speaker unit 31 (see FIG. 2) that is placed at any position in the sealed housing. While the present embodiment uses a speaker as an example of a device for which sound pressure characteristics are to be calculated, the system may be an electromechanical system including an electric circuit such as an actuator and a mechanical element. The computing device 100 includes a processor 101, a communication I / F 102, a memory 103, and a display device 104.

[0018] The processor 101 is, for example, a central processing unit, a digital signal processor, a graphic processing unit, or a field programmable gate array. The processor 101 functions as a controller that manages the overall operation of the computing device 100. The processor 101 performs control processing for overseeing the operation of each unit of the computing device 100, data input / output processing between each unit of the computing device 100, data arithmetic processing, and data storage processing. The processor 101 operates according to a program stored in the memory 103. The processor 101 uses the memory 103 during operation and temporarily stores data generated or acquired by the processor 101 in the memory 103. The processor 101 performs calculation processing for at least one of vibration and sound pressure characteristics of the speaker system 30.

[0019] The communication I / F 102 is an interface circuit that communicates wirelessly or wired with an external device (not shown). Here, I / F refers to an interface. The external device is, for example, a device that can input parameters necessary for calculations. The communication method of the communication I / F 102 is, for example, a wide area network, a local area network, a long term evolution, mobile communication such as 4G or 5G, power line communication, short-range wireless communication (e.g., Bluetooth (registered trademark) communication), or communication for a mobile phone.

[0020] The memory 103 is configured using, for example, Random Access Memory (hereinafter referred to as "RAM") and Read Only Memory (hereinafter referred to as "ROM"), and temporarily stores programs necessary for the operation of the computing device 100, as well as data generated during operation. The RAM is, for example, a work memory used during the operation of the computing device 100. The ROM, for example, stores and holds in advance programs for controlling the computing device 100.

[0021] The display device 104 is a device that displays the results of calculations of the sound pressure characteristics of the speaker system 30 executed by the computing device 100. The display device 104 is, for example, a display or a touch panel display.

[0022] Next, an example of a speaker system 30 according to the present embodiment will be described with reference to Fig. 2. Fig. 2 is a diagram showing an example of a speaker system 30 according to the present embodiment.

[0023] Fig. 2(a) shows a vertical cross section of the speaker system 30. Fig. 2(b) shows a vertical cross section of the internal acoustic space 37 of the housing 32. Fig. 2(c) is an FEM model of the external acoustic space 39.

[0024] FEM model 324 is composed of structural model 520 discretized by element division using two-dimensional or three-dimensional structural elements for speaker unit 31 and housing 32, and spatial model 521 discretized by element division using three-dimensional spatial acoustic elements for internal acoustic space 37 and external acoustic space 39. Speaker unit 31 is composed of diaphragm 20 including a voice coil (not shown), and magnetic circuit 21 consisting of a magnet and yoke (not shown).

[0025] The structural model 520 and the spatial model 521 are set as boundary conditions such that, at least at the diaphragm 20 and the surface of the housing 32 on which the diaphragm 20 is placed, the air particle velocity of the spatial model 521 matches the surface normal velocity of the structural model 520, and the sound pressure of the spatial model 521 matches the surface pressure of the structural model 520.

[0026] In the spatial model 521, a sound absorbing surface 522 is defined on the outermost spherical surface of the housing 32, which is placed in the external acoustic space 39 and is a predetermined distance away from the center of the housing 32. The sound absorbing surface 522 is set with a complex acoustic impedance of a spherical wave that corresponds to the distance from the center of the spatial model 521.

[0027] In addition, in the space model 521, a sound pressure observation point 23 is set at a position 1 m in front of the housing 32. The position of the sound pressure observation point 23 is not limited to 1 m in front of the housing 32 and can be set arbitrarily. The processor 101 outputs the sound pressure characteristics at the sound pressure observation point 23 as the calculation result.

[0028] In the structural model 520, at least one element or virtually connected point (e.g., the center point 35 of the diaphragm) on the model of the voice coil or diaphragm serves as the excitation force application point. Also, in the structural model 520, one point on the magnet or the magnetic circuit 21 including the magnet (e.g., the center of gravity 34 of the magnetic circuit 21) serves as the excitation force reaction force application point. When the speaker unit 31 has an axisymmetric structure, the excitation force application point and the excitation force reaction force application point are preferably located on an axis of symmetry, such as the center point 35 of the diaphragm and the center of gravity 34 of the magnetic circuit. The center point 35, which is the excitation force application point, and the center of gravity 34, which is the excitation force reaction point, are both set to have at least a degree of freedom of movement in the symmetrical axis direction. When load conditions are set, predetermined vibration excitation forces of the same magnitude but in opposite directions are set.

[0029] Although a sealed model of the housing 32 is used, the housing may include an acoustic element such as a bass reflex port or an acoustic horn, in which the internal acoustic space 37 of the housing 32 and the external acoustic space 39 are connected by a spatial element. Furthermore, the housing 32 may be configured as a drone cone, etc., if the same boundary conditions as those of a diaphragm are set. For simplicity, the internal acoustic space 37 in this disclosure does not include modeling of the volume of the portion corresponding to the magnetic circuit 21 and the magnetic gap near the voice coil (not shown), but these may also be included.

[0030] Next, an operation model of the speaker unit 31 will be described with reference to Fig. 3. Fig. 3 is a diagram showing the operation model of the speaker system 30, with the structural model 520 on the right side of the diagram and the electric circuit 111 including the drive circuit on the left side.

[0031] Speaker unit 31 includes electric elements and mechanical elements. The electric elements here are represented by unit electric circuit 10, which is an equivalent circuit model of the electromechanical conversion state of speaker unit 31. Unit electric circuit 10 can be interpreted as an electromechanical energy converter, and converts between electric energy supplied or output between terminals 19 and 16 and mechanical energy supplied or output between terminals 17 and 18. The mechanical elements include diaphragm 20 and magnetic circuit 21. In speaker unit 31, terminals 17 and 18, which are the output and input terminals for mechanical energy input and output of unit electric circuit 10, are connected to diaphragm 20 and magnetic circuit 21.

[0032] The unit electric circuit 10 is represented by a circuit in which the voice coil DC resistance 13, the voice coil inductance 14, and the primary terminals of the electromechanical conversion virtual transformer 15 are connected to DC. The electromechanical conversion virtual transformer 15 is a virtual electronic element that represents the energy conversion between the electric and mechanical elements of the speaker unit 31 as a transformer in an electric circuit. The terminal 24 is grounded. A drive voltage is input to the terminal 11, and a drive current proportional to the drive voltage at the terminal 11 is supplied from the voltage amplifier 12 to the unit electric circuit 10 regardless of load impedance fluctuations. The terminal 18 is connected to the center of gravity 34 of the magnetic circuit 21, and the force acting in the direction of the arrow at the terminal 18 is equal to the force acting in the direction of the arrow at the center of gravity 34. The terminal 17 is connected to the center 35 of the diaphragm 20, and the force acting in the direction of the arrow at the terminal 17 is equal to the force acting in the direction of the arrow at the center 35. The terminal 18 and the center of gravity point 34, and the terminal 17 and the central point 35 may be directly connected, or may be indirectly connected by inserting a connecting member or the like therebetween.

[0033] A drive current flows through the voice coil due to the drive voltage input to terminal 11. When the voice coil is initially stationary, the drive current is the drive voltage divided by the electrical impedance Ze when the diaphragm 20 is stationary. The electrical impedance Ze is expressed by equation (1) using the DC resistance Re and inductance Le of the voice coil.

[0034]

[0035] Here, j represents the current value, and ω represents the angular frequency of the AC current.

[0036] The driving current generates a Lorentz force in the voice coil, which in turn generates a reaction force in the magnetic circuit 21. The Lorentz force generated in the voice coil excites the diaphragm 20, generating a vibration velocity in the diaphragm. If the reaction force generated in the magnetic circuit 21 is considered to act approximately on the center of gravity 34 of the magnetic circuit, the magnetic circuit 21 is excited and generates a vibration velocity. The vibration velocity generated in the voice coil and the diaphragm 20 generates acoustic radiation on the front surface of the diaphragm (outside the housing 32). Sound pressure is also generated on the back surface of the diaphragm 20 (inside the housing 32), which excites the housing 32 and generates acoustic radiation from the housing 32. The vibration velocity generated in the magnetic circuit 21 propagates to the housing 32, generating acoustic radiation to the outside of the housing 32. Furthermore, the vibration propagated to the housing 32 propagates from the back surface of the housing 32 into the internal space, generating internal sound pressure, which vibrates the diaphragm 20 and generates acoustic radiation from the diaphragm 20 to the front surface.

[0037] Thus, when a drive voltage is input to the unit electric circuit 10, a drive current determined by the voice coil's electrical impedance is initially generated. This current acts on the mechanical acoustic system, consisting of the diaphragm 20 and magnet, which are mechanical elements, and vibrates the diaphragm 20 and magnetic circuit 21. Next, as the mechanical acoustic system vibrates, an induced electromotive force is generated in the unit electric circuit 10 in the opposite direction to the drive voltage. This induced electromotive force reduces the voltage effective for generating Lorentz force. This voltage reduction causes an apparent decrease in the vibration velocity of the voice coil and diaphragm. This phenomenon is called electromagnetic damping, and it must be taken into account when accurately calculating the sound pressure of a speaker system. The resulting decrease in vibration velocity acts again from the mechanical acoustic system on the unit electric circuit, reducing the induced electromotive force, which in turn increases the effective voltage. In this way, the unit electric circuit 10 and the mechanical acoustic system, consisting of the diaphragm 20 and magnetic circuit 21, are non-causally interdependent, influencing each other without any time lag. This interdependence must be accurately expressed in order to analyze the sound pressure characteristics of the speaker system 30. One idea is to analyze the sound pressure characteristics of speaker system 30 using a model in which all components of the electrical circuit system and the mechanical acoustic system are discretized, and to analyze all interdependencies using a strongly coupled FEM analysis; however, this would be difficult to implement in practice because the effort required to create the model or the calculation costs would be enormous.

[0038] Conventionally, there are several methods for analyzing the sound pressure characteristics of a speaker system 30. For example, there is a method in which the electrical system of the electric circuit and the mechano-acoustic system of the mechanical elements are analyzed alternately, and the results of each analysis are substituted into each other while performing calculations until a solution converges. This method imposes an enormous computational load because a large-scale FEM analysis of the mechano-acoustic system is performed multiple times until the solution converges.

[0039] There is also a method for analyzing a large-scale FEM model of a mechano-acoustic system by reducing the degrees of freedom and integrating it into a one-dimensional model of an electrical circuit. However, this method has the problem that errors occur when reducing the large-scale FEM model, and that it is difficult to reduce a mechano-acoustic system.

[0040] There is also a method that, following the method disclosed in Patent Document 1, calculates the impedance of a mechanical-acoustic system (hereinafter referred to as "mechanical impedance") by assuming a constant excitation force for a large-scale FEM model of a mechanical-acoustic system, determines an excitation current value for constant voltage driving using the mechanical impedance, and calculates the sound pressure response by resetting the excitation force from the excitation current value. This method has the problem that the calculation process is complicated and time-consuming because large-scale calculations must be performed twice, once to calculate the mechanical impedance and once to calculate the excitation current value.

[0041] As described above, the conventional calculation method has problems in determining the sound pressure characteristics of the speaker system 30, and there is still room for improvement.

[0042] Next, an example of a conventional method for calculating the sound pressure characteristics of the speaker system 30 (a method for determining the mechanical impedance and resetting the excitation force) will be described with reference to Fig. 4. Fig. 4 is a flowchart showing an example of a conventional method for calculating the sound pressure characteristics of the speaker system 30.

[0043] The processor 101 creates FEM model data of the speaker system 30 (step St100). Specifically, the processor 101 sets the components and connection methods of the diaphragm 20, the magnetic circuit 21, the internal acoustic space 37, the external acoustic space 39, and the housing 32 to create an FEM model.

[0044] The processor 101 sets the point of application of the excitation force (hereinafter referred to as the "excitation force application point") and the sound pressure observation point 23 (see FIG. 2) (step St101). The excitation force application point is the point at which the electromagnetic driving force generated in the unit electric circuit 10 acts on the mechanical system (for example, the center of gravity 34 and the central point 35 (see FIG. 3)).

[0045] As a mechanical impedance calculation step, the processor 101 sets the excitation force to be applied to the excitation force application point set in the processing of step St101 (step St102). Since the mechanical impedance is calculated as the ratio of the excitation force applied to the excitation point to the calculation result of the displacement velocity of the excitation point, the excitation force is preferably set to a unit excitation force of 1 to omit the division for calculating the ratio.

[0046] The processor 101 executes calculations under the excitation force conditions set in step St102, and calculates the excitation point displacement velocity corresponding to the mechanical impedance of the excitation force application point (step St103). The calculation method of the processing in step St103 is a known method such as solving the equation of motion in an FEM model.

[0047] In a sound field calculation step, the processor 101 calculates the excitation force at the excitation force application point during constant voltage driving from the excitation point displacement velocity calculated in step St103 (step St104). The calculation method for the processing in step St104 is a method using a known conversion formula disclosed in Patent Document 1.

[0048] The processor 101 resets the excitation force calculated in the processing of step St104 to the excitation force action point (step St105).

[0049] The processor 101 executes calculations under the excitation force conditions set in step St105, and calculates the sound pressure at a predetermined point in the spatial model 521 that includes at least the sound pressure observation point 23 (step St106). The calculation method for the processing in step St106 is the same as that in St103, except for the excitation force conditions given as boundary conditions.

[0050] The processor 101 displays the result of the calculation in the process of step St106 on the display device 104 (step St107).

[0051] As described above, the conventional method for calculating the sound pressure characteristics of the speaker system 30 requires performing large-scale FEM calculations of the mechanical acoustic system twice (steps St103 and St106), which makes the calculation process complicated. In view of this situation, the present disclosure has sought to find a method for calculating the sound pressure characteristics of the speaker system 30 using simpler calculation processes. The new FEM calculation method according to the present disclosure will be described below.

[0052] Next, an operation model of the speaker unit 31 according to this embodiment will be described with reference to Fig. 5. Fig. 5 is a diagram showing the operation model of the speaker unit 31, with the right side of the diagram being a structural model 520 and the left side being an equivalent mechanical element circuit 10A in which the unit electric circuit 10, which does not include a drive circuit, has been replaced with a mechanical component. The equivalent mechanical element circuit is an element block on an FEM model of a mechanical acoustic system that performs operations dynamically equivalent to those of an electric circuit, and is primarily composed of one-dimensional mechanical elements such as springs, dampers, and concentrated masses arranged in space in a circuit pattern.

[0053] In this embodiment, the processor 101 creates an FEM model in which the unit electric circuit 10 shown in Fig. 3 is replaced with an equivalent mechanical element circuit 10A. It is known that the physical phenomena of mechanical systems and electric circuit systems have correlations and similarities, and that analogy conversion is possible, and the conversion of an electric circuit system into a mechanical system is performed in accordance with the fi conversion rule based on known theory (for example, Non-Patent Document 1, p. 37, Table 4.2, force-current analogy column).

[0054] The voice coil DC resistance 13 of the unit electric circuit 10 shown in Fig. 3 is replaced with a damper 44. Here, the mechanical resistance de of the damper is expressed as de = 1 / Re, where Re is the DC resistance of the voice coil.

[0055] 3 is replaced with a spring 43. Here, the mechanical resistance ke of the spring is expressed as ke=1 / Le, where Le is the inductance of the voice coil.

[0056] The damper 44 and the spring 43 are directly or indirectly connected in series to form an electric impedance equivalent mechanical element, which is an element that operates mechanically equivalent to the electric impedance Ze in the electric circuit on the FEM model of the mechanoacoustic system.

[0057] The electromechanical conversion virtual transformer 15 of the unit electric circuit 10 shown in Figure 3 is replaced by a scissors-shaped lever 46. Midpoints 50 and 51 are the fulcrums of the lever 46, and a four-node link is formed between end points 56 and 57 and between driving force application end points 47 and 48. The fulcrum connections at midpoints 50 and 51 allow for parallel movement within a small displacement range. This allows the insulation relationship between the primary and secondary sides of the transformer as an electric circuit element to be expressed by a mechanical model. The operating function of the lever 46 is determined by the ratio of the lengths between the midpoint 50 and the end point 56, the driving force application end point 47, and the ratio of the lengths between the midpoint 50 and the end point 56, the driving force application end point 47, which are set to a force coefficient BL corresponding to the winding ratio of the electromechanical conversion virtual transformer 15. The couple acting between the end points 56, 57 on the left primary side is multiplied by BL between the drive force application end points 47, 48 on the right secondary side, and the relative displacement and relative displacement speed between the end points 56, 57 on the left primary side are multiplied by 1 / BL between the drive force application end points 47, 48 on the right secondary side.

[0058] The spring 43, damper 44, and lever 46 are connected in series in accordance with the connection topology of the voice coil DC resistance 13, voice coil inductance 14, and electromechanical conversion virtual transformer 15 in FIG.

[0059] Connectors 42 and 58 are constrained from displacement in a direction perpendicular to the connection direction between spring 43 and damper 44. In other words, connectors 42 and 58 are displaced only in a component parallel to the connection direction between spring 43 and damper 44. Connector 45 is constrained from displacement in a direction perpendicular to the connection direction between spring 43 and damper 44, and the component parallel to the connection direction is also constrained to an absolute displacement of 0 at ground terminal 49. This allows the equivalent mechanical element circuit 10A to represent a state in which terminal 16 of unit electric circuit 10 is electrically grounded.

[0060] A driving force application end point 47 is connected to the center point 35. The force applied in the direction of the arrow at the driving force application end point 47 is equal to the force applied in the direction of the arrow at the center point 35, and the displacement and displacement speed in the direction of the arrow at the driving force application end point 47 are equal to the displacement and displacement speed in the direction of the arrow at the center point 35. Furthermore, a driving force application end point 48 is connected to the center of gravity 34. The force applied in the direction of the arrow at the driving force application end point 48 is equal to the force applied in the direction of the arrow at the center of gravity 34, and the displacement and displacement speed in the direction of the arrow at the driving force application end point 48 are equal to the displacement and displacement speed in the direction of the arrow at the center of gravity 34. The driving force application end point 48 and the center of gravity 34, and the driving force application end point 47 and the center point 35 may be directly connected, or may be indirectly connected by inserting a connecting member, a displacement constraint calculation formula element, or the like therebetween.

[0061] A forced displacement speed 60 corresponding to the drive voltage input to the terminal 19 of the unit electric circuit 10 (see FIG. 2) is input to the terminal block 41 .

[0062] As described above, connector 58 is constrained so that only the component parallel to the direction in which spring 43 and damper 44 are connected is displaced, but this displacement is constrained by displacement constraint 59 installed on terminal block 41 so that it is equal to forced displacement speed 60. Due to this constraint, the state in which the circuit is driven at a constant voltage by unit electric circuit 10 is also expressed in equivalent mechanical element circuit 10A. Furthermore, when forced displacement speed 60 input to terminal block 41 is 0, terminal block 41 is constrained to an absolute displacement of 0, just like ground terminal 49. Due to this operation, the state in which terminal 19 and terminal 16 are short-circuited to ground in the circuit of unit electric circuit 10 is also expressed in equivalent mechanical element circuit 10A.

[0063] In this way, the unit electric circuit 10 (see FIG. 2) can be replaced with a mechanical element circuit including equivalent mechanical elements. A mechanical element circuit is a model of a virtual mechanical structure configured by mechanical elements.

[0064] In this embodiment, a moving coil type actuator is used as the electromechanical energy converter, and the voice coil is connected to a diaphragm, which is the moving part. However, the electromechanical energy converter is not limited to this, and may be a moving magnet type in which a magnet is disposed on the main moving part side. Also, it may be an electromagnetic type in which a coil is wound around a magnet and a moving iron piece vibrates.

[0065] Next, an example of a method for calculating the sound pressure characteristics of the speaker system 30 according to this embodiment will be described with reference to Fig. 6. Fig. 6 is a flowchart showing an example of a method for calculating the sound pressure characteristics of the speaker system 30 according to this embodiment. Note that the same processes as those in the flowchart of Fig. 4 are designated by the same reference numerals, and their description will be omitted.

[0066] The processor 101 sets an FEM model of mechanical elements equivalent to the electrical circuit (step St202). That is, the processor 101 generates an equivalent mechanical element circuit 10A (see FIG. 5) that is mechanically equivalent to the unit electrical circuit 10 (see FIG. 3) as an FEM model converted based on the known fi conversion law. The necessary elements are a damper 44 (see FIG. 5) that is a mechanical resistance equivalent to the voice coil DC resistance 13 (see FIG. 3), a spring 43 that is equivalent to the voice coil inductance 14 (see FIG. 3), and a scissors-type lever 46 (see FIG. 5) that is equivalent to the electromechanical conversion virtual transformer 15 (see FIG. 3) that represents the force coefficient BL of the electromechanical energy converter in the model of the unit electrical circuit 10. The damper 44 and the spring 43 are connected in series in accordance with the circuit topology of the unit electrical circuit 10 to generate a mechanical circuit equivalent to the electrical impedance Ze of the unit electrical circuit 10. Furthermore, one end of the primary circuit of a scissors-type lever 46 is connected in series to the damper 44 and spring 43, and one end of the series circuit of the primary circuit of the damper 44, spring 43, and scissors-type lever 46 is short-circuited and grounded. Note that if the effect of the electromechanical conversion virtual transformer 15 (see FIG. 3) is converted by a magnification factor when converting the displacement velocity due to the excitation force, the model using the lever 46 is unnecessary. In a model that omits the lever, the element constants of the damper 44 and spring 43 are multiplied by the square of BL, just as the impedance of the primary circuit seen from the secondary side in an electric circuit is multiplied by the square of the turns ratio, and are expressed as de = BL BL / Re and ke = BL BL / Le.

[0067] If the frequency band in which the analysis is performed using the FEM model is a low frequency band and Le, which is the inductance component of the electrical impedance Ze, can be ignored, the spring 43 of the electrical impedance equivalent mechanical element equivalent to Le may be omitted. In other words, even the simplest model of the electrical impedance equivalent mechanical element includes the damper 44.

[0068] Furthermore, the connection order of the series-connected spring 43, damper 44, and lever 46 is not limited to the connection order shown in FIG. 5 , and the terminal to be short-circuited and grounded is not limited to one end of the lever 46. The end to be short-circuited and grounded may be any terminal of the spring 43, damper 44, or lever 46, as long as it is one end of the series-connected elements. Here, a modified equivalent mechanical element circuit will be described using FIG. 7 . FIG. 7 is a diagram showing a modified equivalent mechanical element circuit. For example, in an equivalent mechanical element circuit 200 shown in FIG. 7( a), the spring 43, damper 44, and lever 46 are connected in series in the order of spring 43, lever 46, and damper 44. Furthermore, in an equivalent mechanical element circuit 201 shown in FIG. 7( b), the spring 43, damper 44, and lever 46 are connected in series in the order of lever 46, damper 44, and spring 43.

[0069] Next, the processor 101 connects the driving force application end point of the FEM model of the mechanical element equivalent to the electric circuit to the excitation force application point set in step St101 of the acoustic model creation step (step St203). That is, in the example shown in FIG. 5 , the processor 101 connects the driving force application end point 47 of the secondary circuit of the scissors lever of the equivalent mechanical element circuit 10A to the center point 35, and the driving force application end point 48 of the secondary circuit to the center of gravity 34. Note that if the displacement of the reaction point of the excitation force can be ignored, i.e., if the displacement of the magnetic circuit 21 is set to zero, the lever 46 becomes a grounded type, and the lower half of the lever 46, the connector 45, and the ground terminal 49 can be omitted by constraining the midpoint 50 to an absolute displacement of zero. Furthermore, in a model that omits the lever, the damper 44 and spring 43 are directly connected in series to the center point 35, and the center of gravity 34 is directly short-circuited to ground. In this way, the processor 101 places an equivalent mechanical element circuit in virtual space that includes at least an electrical impedance equivalent mechanical element having properties that are mechanically equivalent to the electrical impedance Ze of the electronic circuit through the processing of steps St202 and St203.

[0070] Next, the processor 101 defines an endpoint for inputting the displacement velocity for vibrating the equivalent mechanical element circuit 10A (step St204). The processor 101 defines a terminal (e.g., the terminal block 41 in FIG. 5 ) corresponding to the terminal 19 in the electric circuit 111 that supplies electrical energy to the unit electric circuit 10 as the endpoint for inputting the displacement velocity for vibrating the equivalent mechanical element circuit 10A, which is the primary side, i.e., electrical side, of the equivalent mechanical element circuit 10A. This definition sets a boundary condition for the endpoint defined in the processing of step St204: that is, a short-circuit to ground when the displacement velocity does not fluctuate. This boundary condition is the same as when the output terminal of the voltage amplifier 12 in the electric circuit 111 is set to zero internal resistance and is short-circuited to ground in passive AC operation. Note that the endpoint defined here may be the lever-side endpoint 57, and the processor 101 sets a value proportional to the drive voltage input to the terminal 19 of the unit electric circuit 10 as the displacement velocity for the voltage application side endpoint. The proportionality constant is 1 when a scissors-type lever model is used. In a model that omits the effect of the electromechanical conversion virtual transformer 15 (see FIG. 3), the proportionality constant is set to a multiplication factor of the reciprocal of BL, which represents the force coefficient in the model of the unit electric circuit 10. The end point on the side other than the voltage application side is short-circuited to ground.

[0071] Next, the processor 101 sets the displacement speed equivalent to the drive voltage input to the terminal 19 of the unit electric circuit 10 to the endpoint defined in the processing of step St204 (step St205). Here, in order to calculate the sound pressure frequency characteristic for a predetermined sinusoidal voltage input of the speaker system 30, the processor 101 sets the excitation frequency and velocity amplitude of the excitation displacement speed that are numerically equal to the frequency and amplitude of the input sinusoidal voltage. In the processing of steps St204 and St205, the processor 101 sets the endpoint for inputting the excitation displacement speed and the displacement speed equivalent to the drive voltage input to the terminal 19 of the unit electric circuit 10.

[0072] The processor 101 calculates the sound pressure characteristics of the speaker system 30 using the FEM model set in the processing of steps St100, St101, St202, St203, St204, and St205 (step St206). The processor 101 calculates, in a single strong coupling calculation, the mutual influence in the mechano-acoustic system including the mechanistic FEM model 523 consisting of the equivalent mechanical element circuit 10A and the structural model 520, and the spatial model 521 including the set boundary conditions with the structural model 520. In other words, the processor 101 calculates the sound pressure characteristics of the speaker system 30 in a single large-scale calculation.

[0073] The processor 101 displays the result of the calculation performed in step St206 on the display device 104 (step St107).

[0074] As described above, the computing device 100 according to this embodiment can calculate the sound pressure characteristics of the speaker system 30 in a single large-scale calculation by using an FEM model in which electric circuits are replaced with equivalent mechanical element circuits and integrated into a mechanical acoustic system. In other words, the computing device 100 can reduce the number of times that complex large-scale calculations are performed without reducing the accuracy of the calculations, thereby reducing the time required for the calculation processing. Furthermore, the computing device 100 can reduce the load on the processor 101 required for the calculation processing.

[0075] Next, the numerical calculation model data describing the calculation method according to this embodiment will be described with reference to Figures 8, 9, and 10. Figure 8 is a diagram showing definitions of node names. Figures 9 and 10 are diagrams showing examples of the numerical calculation model data.

[0076] The names of the nodes are defined as shown in Fig. 8. The center point 35 is defined as "GRID101", the center of gravity point 34 as "GRID102", the driving force application end point 47 as "GRID201", the driving force application end point 48 as "GRID202", the intermediate point 50 as "GRID203", the intermediate point 51 as "GRID204", the connector 58 as "GRID211", the connectors 42 as "GRID212" and "GRID213", and the connector 45 as "GRID214".

[0077] The numerical calculation model data DA1 and the numerical calculation model data DA2 are in a data format conforming to Nastran. The numerical calculation model data DA1 and the numerical calculation model data DA2 are an example of a data structure describing the calculation method according to this embodiment shown in Fig. 6. The numerical calculation model data DA1 includes data D1, data D2, and data D3. The numerical calculation model data DA2 includes data D4, data D5, and data D6.

[0078] Data D1 is a data structure describing the processing content defined in the acoustic model creation steps (steps St100 and St101) of the flowchart shown in Figure 6. Data D1 defines the components and connection methods of the diaphragm 20, magnetic circuit 21, internal acoustic space 37, external acoustic space 39, and housing 32 (not shown), and in addition to the set FEM model, defines the coordinates of GRID101 (i.e., center point 35, which is the excitation point of the diaphragm 20) and GRID102 (i.e., center of gravity point 34, which is the excitation point of the equivalent mechanical element circuit 10A). The node definition line of data D1 includes, in the stated order, a node definition declaration, a node number, the X coordinate of the node, the Y coordinate of the node, and the Z coordinate of the node. For example, "GRID 101 -20.0 100.0 0.0".

[0079] Next, data D2 has a data structure that describes the processing content of step St202, which is a step of placing a mechanical element circuit equivalent to an electric circuit in the flowchart shown in FIG.

[0080] In data D2, the coordinates of each of GRID201, GRID202, GRID203, GRID204, GRID211, GRID212, GRID213, and GRID214 are defined as node definitions. Data D2 includes, in the stated order, a node definition declaration, a node number, the X coordinate of the node, the Y coordinate of the node, and the Z coordinate of the node.

[0081] In data D2, a damper 44, which is a virtual mechanical element, is defined. CDAMP2 defines the element of the damper 44. The damper definition line in CDAMP2 includes, in the order listed, a damper definition declaration, a unique element identification number, the damper's mechanical resistance, the node number of node 1, a component number in the displacement coordinate system that defines the displacement direction of node 1 specified in the CD entry of the GRID data, the node number of node 2, and a component number in the displacement coordinate system that defines the displacement direction of node 2 specified in the CD entry of the GRID data. Here, the CD entry represents the identification number of the coordinate system in which the displacement, degrees of freedom, constraints, and solution vectors are defined at the node. In data D2, the CDAMP2 definition line is "CDAMP2 14 1.4706-4 212 1 213 1," and defines that a damper 44 exists between GRID212 and GRID213, with a mechanical resistance of "1.4706-4 Ns / mm," which corresponds to an electrical resistance of 6.4 Ω. The mechanical resistance value of the damper 44 is input as ke=1 / Re.

[0082] Data D2 defines a spring 43, which is a virtual mechanical element. CELAS2 defines the element of spring 43. The spring definition line of CELAS2 includes, in order of description, a spring definition declaration, a unique element identification number, a spring constant, the node number of node 1, a component number in the displacement coordinate system that defines the displacement direction of node 1 specified in the CD entry of the GRID data, the node number of node 2, and a component number in the displacement coordinate system that defines the displacement direction of node 2 specified in the CD entry of the GRID data. In data D2, the CELAS2 definition line is "CELAS2 15 25.0 211 1 212 1," and defines that a spring 43 exists between GRID213 and GRID214, with a spring constant of "25 N / mm," which corresponds to an electrical inductance of 0.04 mH. The spring constant of spring 43 is input as ke = 1 / Le.

[0083] Data D2 defines a scissors-type lever 46. The MPC defines constraint equations between multiple nodes that make up the lever 46. The MPC definition line includes, in the order they are written, a multi-point constraint declaration, a unique element identification number, a node number, a component number of the coordinates constrained by the MPC at the node, and a node mobility magnification coefficient. The node number, component number, and mobility magnification coefficient are repeated for each node whose degrees of freedom are constrained by the MPC. In data D2, "MPC 21 201 1 4.29 203 1 -5.29 213 1 1.0" defines a constraint condition that limits the degrees of freedom so that the total displacement of 4.29 times the X displacement of GRID201, -5.29 times the X displacement of GRID203, and 1.0 times the X displacement of GRID213 is always 0. This constraint constrains the relative displacement between GRID 213 and GRID 203 to 4.29 times the relative displacement between GRID 201 and GRID 203. In other words, when the displacement magnification of the lever is defined as BL, MPC defines a lever where BL = 4.29, the fulcrum is midpoint 50, and includes driving force application end point 47. In data D2, "MPC 22 202 1 4.29 204 1 -5.29 214 1 1.0" defines a constraint condition that limits the degrees of freedom so that the total displacement of 4.29 times the X displacement of GRID 202, -5.29 times the X displacement of GRID 204, and 1.0 times the X displacement of GRID 214 is always 0. This constraint constrains the relative displacement between GRID 214 and GRID 204 to 4.29 times the relative displacement between GRID 202 and GRID 204. In other words, when the displacement magnification of the lever is BL, the MPC defines a lever with BL=4.29, a fulcrum at midpoint 51, and including drive force application end point 48. In data D2, "MPC 23 203 1 1.0 204 1 -1.0" defines a constraint condition that limits the degrees of freedom so that the total displacement of 1.0 times the X displacement of GRID 203 and -1.0 times the X displacement of GRID 204 is always 0. This constraint constrains the X displacements of GRID 203 and GRID 204 to always be equal. In other words, the MPC defines the connected parallel movement between midpoint 50, which is the fulcrum of the right lever, and midpoint 51 of the left lever.

[0084] Next, data D3 is a data structure describing the processing content of step St203, which is a step of arranging a mechanical element circuit equivalent to the electric circuit in the flowchart shown in Figure 6. In data D3, "MPC 24 201 1 1.0 101 1 -1.0" defines that the driving force application end point 47 of lever 46 is connected to center point 35, which is the excitation point of diaphragm 20, and that the degree of freedom in the X direction is shared. In data D3, "MPC 25 202 1 1.0 102 1 -1.0" defines that the driving force application end point 48 of lever 46 is connected to center point 34, which is the excitation point of structural model 520.

[0085] As described above, the data D1, D2, and D3 define the positional relationships and connection conditions of the components of the equivalent mechanical element circuit.

[0086] Next, data D4 has a data structure that describes the processing content of step St204 of the vibration displacement speed setting step in the flowchart shown in FIG.

[0087] Data D4 defines the endpoints for inputting the displacement velocity that excites the equivalent mechanical element circuit 10A. SPCs define the constraint conditions for the degrees of freedom of the nodes. SPCs include, in the order listed, a single-point constraint declaration, an identification number, a node number, a component number, and a forced displacement value. In data D4, "SPC 30 211 1 0.0" defines that the X degree of freedom of GRID 211 (i.e., terminal block 41) is temporarily constrained to a displacement of 0. Furthermore, "SPC 30 214 1 0.0" defines that the X degree of freedom of GRID 214 (i.e., endpoint 57) is temporarily constrained to a displacement of 0. These endpoints correspond to terminals 19 and 16, which are input terminals in the corresponding unit electrical circuit 10, and passively represent that both terminals are grounded. In this embodiment, terminal 16 is permanently grounded and terminal 19 is driven by a constant voltage, so a forced displacement constraint by SPCD is defined on GRID 211 (i.e., terminal block 41) corresponding to terminal 19. The SPCD includes, in the stated order, a forced drive declaration, an identification number, a node number, a component number, and a forced displacement amplitude magnification. In data D4, "SPCD 31 211 1 1.0" defines that either a forced displacement velocity or a forced displacement acceleration is applied to GRID 211 (i.e., terminal block 41) at a value 1.0 times the set value.

[0088] As described above, data D4 defines the position where the boundary condition of the displacement velocity is input.

[0089] Next, data D5 has a data structure that describes the processing content of step St205 of the vibration displacement speed setting step in the flowchart shown in FIG.

[0090] Data D5 defines a frequency table of excitation force and the like.

[0091] RLOAD1 defines the type of contact load. RLOAD1 includes, in this order, the following values: dynamic load declaration, identification number, amplitude definition identification number, initial time delay, initial phase, amplitude definition real part table identification number, amplitude definition imaginary part table identification number, and load type. In data D5, "RLOAD1 41 31 0 0 1 0 VELO" defines the forced displacement in the X direction set in GRID 211 by identification number 31, i.e., SPCD 31, as a nodal load with a load type of VELO, i.e., forced displacement velocity, with the initial time delay and initial phase both set to 0, and with reference to a table whose complex amplitude real part is defined by identification number 1, i.e., TABLED1 1, described below, and whose imaginary part is 0.

[0092] FREQ2 defines the frequency of the displacement velocity. FREQ2 includes the values ​​of a logarithmic interval frequency table declaration, an identification number, a start frequency, an end frequency, and the number of points, in the stated order. In data D5, "FREQ2 13 10.0 100000.0 401" defines a frequency column vector of 401 points, spaced logarithmically, i.e., geometrically, between RLOAD15 and 100 kHz.

[0093] TABLE1 defines a tabular function of displacement velocity. TABLE1 includes, in the order listed, a general table declaration, an identification number, a designation as to whether the X-axis interpolation is linear or logarithmic, and a designation as to whether the Y-axis interpolation is linear or logarithmic. TABLE1 also includes, in subsequent lines, a line continuation flag, a table value, and an end flag. In data D5, TABLE1 contains "TABLE1 1 LINEAR LINEAR" and, in the subsequent line, "+ 0.0 2828.4 20000.0 2828.4 END," which indicate that the X-axis interpolation and the Y-axis interpolation are linear. Furthermore, the numerical values ​​shown under TABLE D1 are X1: 0.0 Y1: 2828.4 X2: 20000.0 Y2: 2828.4, and the value on the Y axis is a displacement velocity of 2828.4 mm / s equivalent to a constant applied voltage of 2.8284 V when an acoustic input equivalent to 1 W is injected into a speaker unit with a nominal impedance of 8 Ω.

[0094] As described above, data D5 defines the boundary conditions of the displacement velocity.

[0095] Next, data D6 has a data structure that describes the processing content of step St206 of the calculation execution step in the flowchart shown in FIG.

[0096] Data D6 unifies the boundary conditions and constraint conditions required for executing the calculation and defines the method for executing the analytical calculation.

[0097] DLOAD defines the superposition of dynamic loads. DLOAD includes, in the order listed, the following values: dynamic load superposition declaration, identification number, final scale, and a set of one or more RLOAD scales and RLOAD identification numbers. In data D5, "DLOAD 12 1.0 1.0 41" defines the load condition DLOAD12, in which the external force defined by identification number 41, i.e., RLOAD41, is multiplied by an individual scale of 1.0, superimposed with other RLOADs, and then multiplied by an overall scale of 1.0. In this embodiment, only one RLOAD is superimposed, but multiple RLOADs may be used.

[0098] MPCADD unifies multi-point constrained MPCs. MPCADD includes, in the order described, a unification declaration, an identification number, and the value of one or more MPC identification numbers. In data D6, "MPCADD 20 21 22 23 24 25" unifies the multi-point constrained MPCs defined by identification numbers 21, 22, 23, 24, and 25, i.e., MPCs 21, 22, 23, 24, and 25, into one and defines it as MPCADD 20.

[0099] SPCADD unifies single-point constraint SPCs. SPCADD includes, in the order described, a unification declaration, an identification number, and a single or multiple SPC identification number. In data D6, "SPCADD 7 30 35" unifies the single-point constraint SPCs defined by identification numbers 30 and 35, i.e., SPCs 30 and 35, and defines them as a new SPCADD 7. In this embodiment, SPC 35 includes SPCs defined in SPC rows (not shown) as constraint conditions that constrain all degrees of freedom except for translation in the X-axis direction at all nodes included in the equivalent mechanical element circuit 10A, i.e., GRIDs 201, 202, 203, 204, 211, 212, 213, and 214.

[0100] ANALYSIS DFREQ defines that a FEM analysis is to be performed using a direct frequency response analysis. SPC= defines the unified single-point constraint conditions used in the calculation, MPC= defines the unified multi-point constraint conditions used in the calculation, FREQUENCY= defines the frequency table for calculating the frequency response, and DLOAD defines the load conditions used in the calculation, each defined by an identification number.

[0101] As described above, the numerical calculation model data DA1 and the numerical calculation model data DA2 describe the calculation method according to this embodiment shown in the flowchart of Fig. 6. By using the numerical calculation model data DA1 and the numerical calculation model data DA2, the processor 101 can analyze the sound pressure characteristics of the speaker system 30 using an FEM model in which an electric circuit is converted into an equivalent mechanical element circuit and integrated into a single mechanical acoustic system. Note that the numerical values, data order, etc. of the numerical calculation model data DA1 and the numerical calculation model data DA2 are merely examples and are not limited to the example shown in Fig. 8.

[0102] Next, an example of the calculation results of the sound pressure characteristics of the speaker system 30 will be described with reference to Fig. 11 and Fig. 12. Fig. 11 is a diagram showing an example of the calculation results of the sound pressure characteristics of the speaker system 30. Fig. 12 is a three-dimensional distribution diagram of the calculated sound pressure characteristics of the speaker system 30.

[0103] Graph G1 shown in Fig. 11 has frequency (Hz) on the horizontal axis and sound pressure (dB) on the vertical axis. Graph G1 shows the sound pressure (Measurement) actually observed at sound pressure observation point 23 and the sound pressure (Prediction) at sound pressure observation point 23 calculated using the calculation method according to this embodiment. Graph G1 shows that Measurement and Prediction match with high accuracy. In other words, the calculation method according to this embodiment can analyze the sound pressure characteristics of speaker system 30 with high accuracy.

[0104] 12 is a calculation result of the sound pressure distribution of the speaker system 30 calculated using the calculation method according to this embodiment. The processor 101 displays the sound pressure distribution map G2 on the display device 104. This allows the calculation device 100 to display a distribution map of the calculated sound pressure characteristics of the external acoustic space 39 on the display device 104, thereby helping the user to visually recognize the calculation results in three dimensions.

[0105] Next, a modified example of the voice coil equivalent circuit model of the speaker unit 31 according to the present embodiment will be described with reference to Fig. 13. Fig. 13 is a diagram showing a modified example of the operation model of the speaker unit 31 according to the present embodiment.

[0106] The speaker unit 31 shown in Fig. 13 is a model that takes into account up to the second-order term of the electrical impedance in the electrical circuit. The equivalent mechanical element circuit 10B is a model that is composed of mechanical elements equivalent to the electrical circuit when up to the second-order term of the electrical impedance of the voice coil is taken into account. Components similar to those in the equivalent mechanical element circuit 10A shown in Fig. 5 are designated by the same reference numerals and will not be described again.

[0107] In an electric circuit (not shown) equivalent to the equivalent mechanical element circuit 10B, the electric impedance Ze2 of the circuit is expressed by equation (2).

[0108]

[0109] Here, the third term on the right side of equation (2) is a term for the electrical impedance generated by eddy currents generated inside the conductors of the magnetic circuit 21 and the voice coil. It is generally known that an electrical equivalent circuit can be expressed as a parallel circuit of inductance L2 and electrical resistance R2. In the equivalent mechanical element circuit 10B, the third term on the right side of equation (2) is expressed as a parallel connection of the spring 52 and damper 53, since the topology of the corresponding electrical circuit (not shown) is preserved. The parallel-connected spring 52 and damper 53 are further connected in series to the spring 43. The resistance k2 of the spring 52 is k2 = 1 / L2. The mechanical resistance d2 of the damper 53 is d2 = 1 / R2. The connector 55 displaces only in a direction parallel to the direction in which the spring 43 and damper 44 are connected. The displacement speed for vibrating the equivalent mechanical element circuit 10B is input to the end point 54 from the termination block 41, as in the equivalent mechanical element circuit 10A.

[0110] As a result, the processor 101 can analyze the sound pressure characteristics of the speaker system 30 in a single large-scale FEM analysis by generating an FEM model that converts the electric circuit into a mechanical element circuit equivalent to the electric circuit, even if the model takes into account up to the second-order term of the electric impedance of the electric circuit, and performing calculations.

[0111] <Modifications> Next, with reference to Figures 14, 15, 16, 17, 18, 19, and 20, a modification of FEM model 324 according to this embodiment, in which multiple speaker units are mounted on a housing, will be described. Figures 14, 15, and 16 show an FEM model 624 that is a modification of FEM model 324 according to this embodiment, and Figure 14 shows a structural model 620. Figure 15 shows an internal acoustic space 637. Figure 16 shows an external acoustic space 639. Internal acoustic space 637 and external acoustic space 639 form a space model 621. Figure 17 shows a drive circuit for driving multiple speaker units in parallel.

[0112] 14 is an FEM structural model of a speaker system 630 in which speaker unit 31A and speaker unit 31B, which are the same as speaker unit 31, are mounted one above the other in a sealed housing 632. The computing device 100 sets, as in the case of the structural model 520 and the spatial model 621, a boundary condition for the structural model 620 and the spatial model 621, where the air particle velocity of the spatial model 621 matches the velocity normal to the surface of the structural model 620 between diaphragms 20A and 20B and the surface of the housing 632 on which they are arranged. The computing device 100 also sets, as a boundary condition for the structural model 620 and the spatial model 621, a condition for the sound pressure of the spatial model 621 to match the surface pressure of the structural model 620 between diaphragms 20A and 20B and the surface of the housing 632 on which they are arranged. With this setting, the two speaker units 31A and 31B are not only connected by the housing 632, but also form a FEM that is strongly coupled by the two parameters of the spatial model 621, namely, sound pressure and particle velocity.

[0113] In this modification, two speaker units 31A and 31B are driven in parallel by the electrical circuit shown in FIG. 17 . The driving voltage and driving current supplied from the voltage amplifier 12 are supplied to the speaker unit 31A via electrical terminals 619A and 616A, and to the speaker unit 31B via electrical terminals 619B and 616B. FIG. 18 is a model diagram in which the parallel-configured electrical circuit is replaced with an equivalent mechanical circuit. Here, the computing device 100 creates equivalent mechanical element circuits 610BA and 610BB (see FIGS. 19 and 20 ), which will be described later, as equivalent mechanical element circuits for each unit. The computing device 100 temporarily deletes the terminal blocks 41A and 41B at the driving ends from the equivalent mechanical element circuits 610BA and 610BB. Thereafter, instead of using connectors 54A and 54B, the computing device 100 connects equivalent mechanical element circuits 610BA and 610BB using connector 654, which has a degree of freedom only in the input direction of forced displacement velocity 660 (i.e., the horizontal direction of the screen). Similar to the equivalent mechanical element circuit 10B of speaker unit 31 (see FIG. 13), the computing device 100 places a terminal block 641 at the end of the connected circuits. The terminal block 641 is constrained by a displacement constraint 659 so that the displacement velocity is equal to forced displacement velocity 660. Similarly to the speaker unit 31 (see FIG. 5), the computing device 100 connects a driving force application end point 47A on the secondary side of scissors-shaped lever 46A to a center point 35A of the diaphragm of speaker unit 31A. The computing device 100 also connects a driving force application end point 48A on the secondary side of the lever 46A to the center of gravity 34A of the magnet of the speaker unit 31A. The computing device 100 also connects a driving force application end point 47B on the secondary side of the lever 46B to the center of gravity 35B of the diaphragm of the speaker unit 31B. The computing device 100 also connects a driving force application end point 48B on the secondary side of the lever 46B to the center of gravity 34B of the magnet of the speaker unit 31B. The other components, namely, connectors 42A, 45A, 55A, 42B, 45B, and 55B, operate in the same manner as connectors 42, 45, and 58, which are components of the speaker unit 31 (see FIG. 5), and therefore will not be described here.Furthermore, the terminal points 56A, 57A, 56B, and 57B operate in the same manner as the terminal points 56 and 57 of the speaker unit 31 (see FIG. 5), and therefore a description thereof will be omitted. The dampers 43A, 53A, 43B, and 53B operate in the same manner as the damper 44 of the speaker unit 31 (see FIG. 5), and therefore a description thereof will be omitted. The springs 44A, 52A, 44B, and 52B operate in the same manner as the spring 43 of the speaker unit 31 (see FIG. 5), and therefore a description thereof will be omitted. The levers 46A and 46B operate in the same manner as the lever 46 of the speaker unit 31 (see FIG. 5), and therefore a description thereof will be omitted. The ground terminals 49A and 49B operate in the same manner as the ground terminal 49 of the speaker unit 31 (see FIG. 5), and therefore a description thereof will be omitted. The arrangement order of the component elements arranged in series differs between the equivalent mechanical element circuit 10B of the speaker unit 31 (see FIG. 13) and the equivalent mechanical element circuit 610B of this modified example, but the arrangement order of these elements may be the arrangement order exemplified in the equivalent mechanical element circuit 10B and the equivalent mechanical element circuit 610B or any other arrangement order, as long as they are arranged in series.

[0114] Using this equivalent mechanical element circuit 610B, structural model 620, and spatial model 621, the computing device 100 applies a forced displacement velocity 660 to the terminal block 641 while correctly reflecting the mutual influence between the units. That is, the computing device 100 first places an end point (here, the terminal block 641 of the connector 654) that connects multiple end points or nodes indirectly connected to the end points of the equivalent mechanical element circuits of the speaker unit 31A and the speaker unit 31B. The computing device 100 then sets, as a boundary condition, a forced displacement velocity 660 equivalent to the drive voltage supplied from the voltage amplifier 12 to the terminal block 641, which is the end point connecting the multiple end points. This allows the computing device 100 to calculate the total sound pressure of the sound reproduced by a speaker system having two units driven in parallel in a single calculation.

[0115] Here, by further modifying the equivalent mechanical element circuit 610B, the computing device 100 can calculate the total sound pressure by separating it into the contributions of the speaker unit 31A and the speaker unit 31B. Fig. 19 is a diagram showing an equivalent mechanical element circuit for calculating the sound pressure contribution of the speaker unit 31A. Fig. 20 is a diagram showing an equivalent mechanical element circuit for calculating the sound pressure contribution of the speaker unit 31B.

[0116] When creating a model of a single-unit drive state from a model of a dual-unit drive state, care must be taken when handling the electrical input terminal of the non-driven unit. In actuality, if you simply disconnect the drive wiring on the non-driven unit, leaving it open, and drive only the other unit, the pressure fluctuations within the cabinet and the propagation of sound pressure through the external acoustic space will cause the diaphragm on the non-driven unit to vibrate, resulting in behavior similar to that of a drone cone. Even if you swap the driven and non-driven units in this drone cone state and measure and add up the sound pressures, it will not result in the sound pressure of a parallel drive. The reason for this phenomenon is that in a parallel drive state using a voltage-amplifying amplifier, regardless of the drive voltage, the amplifier output terminal (i.e., the speaker unit input terminal) is passively short-circuited in terms of AC, which means that electromagnetic damping is highly effective, and this cannot be reproduced by simply opening the wiring.

[0117] Therefore, in the one-sided drive model of this modification, an equivalent mechanical element circuit is configured so that the electrical terminals of the non-drive unit are short-circuited. Specifically, as shown in FIGS. 19 and 20 , the computing device 100 removes connector 654 from equivalent mechanical element circuit 610B, connects connector 54A to spring 44A, and connects connector 54B to spring 44B. The computing device 100 connects terminal block 41A to connector 54A and terminal block 41B to connector 54B, thereby arranging equivalent mechanical element circuits 610BA and 610BB, which are equivalent mechanical element circuits of speaker units 31A and 31B. The computing device 100 sets boundary conditions for terminal block 41A and terminal block 41B, constraining their displacement to a predetermined displacement speed using displacement constraints 59A and 59B. The computing device 100 can configure a model that passively enters a short-circuit state using displacement constraints 59A and 59B. 19, the computing device 100 applies a forced displacement velocity 660A to the terminal block 41A connected to the speaker unit 31A, and sets or does not set the displacement velocity of the terminal block 41B to 0 (zero), thereby calculating the sound pressure contribution of the speaker unit 31A. In FIG. 20, the computing device 100 applies a forced displacement velocity 660B to the terminal block 41B connected to the speaker unit 31B, and sets or does not set the displacement velocity of the terminal block 41A to 0 (zero), thereby calculating the sound pressure contribution of the speaker unit 31B. In other words, when the computing device 100 sets the forced displacement velocity 660 corresponding to the drive voltage to the same value as the forced displacement velocity 660A and the forced displacement velocity 660B, the sound pressure of the parallel drive model is calculated by superimposing the sound pressure of the one-sided drive one-sided short-circuit model.

[0118] In this manner, the computing device 100 first arranges an equivalent mechanical element circuit 610BA of the speaker unit 31A and an equivalent mechanical element circuit 610BB of the speaker unit 31B. The computing device 100 sets boundary conditions that constrain all of the nodes (terminal blocks 41A and 41B in this modification) that are either endpoints of the respective equivalent mechanical element circuits or that are indirectly connected to the endpoints to a predetermined displacement velocity (forced displacement velocity 660A, forced displacement velocity 660B in this modification). The boundary conditions set here set a non-zero predetermined displacement velocity (forced displacement velocity 660A, forced displacement velocity 660B in this modification) at one of the endpoints of one of the multiple equivalent mechanical element circuits (equivalent mechanical element circuit 610BA, equivalent mechanical element circuit 610BB in this modification), and set the displacement velocity input to the endpoints or nodes of the other equivalent mechanical element circuits to 0 (zero).

[0119] This allows the computing device 100 to calculate the sound pressure contribution of a single speaker unit to a speaker system including multiple speaker units. Conventionally, when calculating the sound pressure of a complex speaker system including multiple speaker units, the calculation of the mutual influence between the multiple speaker units is particularly cumbersome, resulting in time-consuming or difficult analysis. However, the computing device 100 can easily calculate the sound pressure even in a complex speaker system by configuring an equivalent mechanical element circuit so that the electrical terminals of the non-driven units are short-circuited, thereby accurately calculating the sound pressure contribution of each speaker unit and calculating the total sound pressure using the principle of superposition. Furthermore, because the computing device 100 can accurately calculate the sound pressure contribution of each speaker unit in a speaker system including multiple speaker units, it can assist a user in modifying the design of the speaker system so that the total sound pressure becomes a desired sound pressure based on the sound pressure contribution of each speaker unit. In this embodiment, the procedure for separating the mutual influences of multiple electromechanical energy converters has been described using the example of calculating the sound pressure transfer function of a speaker, but the present disclosure is not limited to such an example. For example, the procedure disclosed herein can also be used as a procedure for separating mechanical vibrations at a predetermined position on a mechanical device, which are excited by the mechanical device on which multiple voice coil actuators are arranged, into vibration contributions from each actuator as transfer functions.

[0120] Next, with reference to Figures 21, 22, 23, 24, 25, 26, and 27, a modified example of a two-way speaker system modeled using FEM model 324 according to this embodiment, in which a plurality of speaker units connected by a network circuit are installed, will be described. Figures 21, 22, and 23 show an FEM model 724, which is a modified example of FEM model 324 according to this embodiment. Figure 21 shows a structural model 720. Figure 22 shows an internal acoustic space 737. Figure 23 shows an external acoustic space 739. The internal acoustic space 737 and the external acoustic space 739 form a space model 721. Figure 24 shows a drive circuit for a two-way speaker including a network circuit.

[0121] 21 is an FEM structural model of a speaker system 730 in which a speaker unit 31B, the same as the speaker unit 31 (see FIG. 5 ), is arranged as a woofer in a lower section of a sealed housing 732, and a tweeter unit 31C for reproducing high frequencies is arranged in an upper section. The computing device 100 sets, as a boundary condition for the structural model 720 and the spatial model 621, a condition that the air particle velocity of the spatial model 721 matches the surface normal velocity of the structural model 720 between the diaphragms 20C and 20B and the surface of the housing 732 on which they are arranged, similar to the structural model 520 and the spatial model 521. The computing device 100 also sets, as a boundary condition for the structural model 720 and the spatial model 621, a condition that the sound pressure of the spatial model 721 matches the surface pressure of the structural model 720 between the diaphragms 20C and 20B and the surface of the housing 732 on which they are arranged. With this setting, the two tweeter units 31C and speaker unit 31B are not only connected by the housing 732, but also form an FEM that is strongly coupled by two parameters, sound pressure and particle velocity, which are parameters of the spatial model 721. However, in this modified example, the back space of the tweeter unit does not communicate with the internal acoustic space 737 of the cabinet, and the coupling between units by the spatial model is a model that is limited to coupling on the diaphragm surface.

[0122] In this modification, the two tweeter units 31C and the speaker unit 31B are driven in parallel by the electrical circuit shown in FIG. 24 . The dividing network circuit 790 is an electrical circuit including the tweeter unit 31C and the speaker unit 31B. The driving voltage and driving current supplied from the voltage amplifier 12 are supplied to the tweeter unit 31C via a high-pass filter formed by a high-pass filter capacitor 704 and a high-pass filter coil 703, through electrical terminals 719C and 716C. The driving voltage and driving current supplied from the voltage amplifier 12 are supplied to the speaker unit 31B via a low-pass filter formed by a low-pass filter capacitor 701 and a low-pass filter coil 702, through electrical terminals 719B and 716B. FIG. 25 is a model diagram in which the parallel-configured network circuit and the speaker unit electrical circuit are replaced with equivalent mechanical circuits. Here, the computing device 100 creates tweeter equivalent mechanical element circuits with the same configuration as equivalent mechanical element circuits 610BA and 610BB (see FIGS. 19 and 20) as equivalent mechanical element circuits for each unit, but with the parameters of each element replaced with the parameters of tweeter unit 31C. The computing device 100 temporarily deletes low-pass filter termination block 741B at the driving end and high-pass filter termination block 741C at the driving end of the tweeter equivalent mechanical element circuit from equivalent mechanical element circuits 710BC and 710BB. The computing device 100 then adds and places components equivalent to the network circuit of FIG. 24.

[0123] As components equivalent to a network circuit, the computing device 100 arranges, in an equivalent mechanical element circuit connected to the speaker unit 31B, a low-pass filter relative acceleration proportional mass 701M corresponding to the low-pass filter capacitor 701 and a low-pass filter coil equivalent spring 702M corresponding to the low-pass filter coil 702, which are low-pass filter components for the woofer. Also, as components equivalent to a network circuit, the computing device 100 arranges, in an equivalent mechanical element circuit connected to the tweeter unit 31C, a high-pass filter coil equivalent spring 703M corresponding to the high-pass filter coil 703 and a high-pass filter relative acceleration proportional mass 704M corresponding to the high-pass filter capacitor 704, which are high-pass filter components for the woofer.

[0124] The computing device 100 connects the arranged components so as to preserve and trace the circuit topology of FIG. 24 . One end of the low-pass filter relative acceleration proportional mass 701M is mechanically grounded to the displacement constraint 759B via a connector 753B, and the other end is connected to a connector 754B at the drive end of the speaker unit 31B. One end of the high-pass filter coil equivalent spring 703M is connected to a connector 754B, and the other end is connected to a connector 754 that connects the woofer circuit and the tweeter circuit. One end of the tweeter-side high-pass filter coil equivalent spring 703M is mechanically grounded to the displacement constraint 759C via a connector 753C, and the other end is connected to a connector 754C at the drive end of the tweeter unit 31C. One end of high-pass filter relative acceleration proportional mass 704M is connected to connector 754C, and the other end is connected to connector 754, which connects the woofer circuit and tweeter circuit. Connector 754, like connector 654, has its driving end connected to termination block 741, and is constrained by displacement constraint 759 so that the displacement speed is equal to forced displacement speed 760.

[0125] The computing device 100 connects the secondary driving force application end point 47C of the tweeter's scissors-shaped lever 46C to the center point 35C of the diaphragm of the tweeter unit 31C, as in the case of the speaker unit 31. The computing device 100 also connects the secondary driving force application end point 48C of the tweeter's scissors-shaped lever 46C to the center of gravity point 34C of the magnet of the tweeter unit 31C. As other tweeter components, connectors 42C, 45C, and 55C operate in the same manner as connectors 42, 45, and 58 of the speaker unit 31 (see FIG. 5), and therefore their description will be omitted. Furthermore, dampers 43C and 53C operate in the same manner as damper 44 of the speaker unit 31 (see FIG. 5), and therefore their description will be omitted. Furthermore, springs 44C and 52C operate in the same manner as spring 43 of speaker unit 31 (see FIG. 5), and therefore explanation thereof will be omitted. Furthermore, lever 46C operates in the same manner as lever 46 of speaker unit 31 (see FIG. 5), and therefore explanation thereof will be omitted. Furthermore, ground terminals 49C, 739C, and 739B operate in the same manner as ground terminal 49 of speaker unit 31 (see FIG. 5), and therefore explanation thereof will be omitted. Furthermore, terminals 56C and 57C operate in the same manner as terminals 56 and 57 of speaker unit 31 (see FIG. 5), and therefore explanation thereof will be omitted. Note that the equivalent mechanical element circuit 10B of speaker unit 31 and the equivalent mechanical element circuit 710B of this modification differ in the arrangement order of the component elements arranged in series, but the arrangement order of these elements may be the arrangement order exemplified in equivalent mechanical element circuit 10B and equivalent mechanical element circuit 610B or any other arrangement order, as long as they are arranged in series.

[0126] The computing device 100 uses this equivalent mechanical element circuit 710B, structural model 720, and spatial model 721 to apply a forced displacement velocity 760 to the termination block 741 while correctly reflecting the mutual influence between the units. This allows the computing device 100 to calculate, in a single calculation, the total sound pressure of the reproduced sound from a two-way speaker system equipped with multiple speaker units connected by a network circuit.

[0127] Here, by further modifying the equivalent mechanical element circuit 710B, the computing device 100 can calculate the total sound pressure by separating it into the contributions of the tweeter unit 31C and the speaker unit 31B. Fig. 26 is a diagram showing an equivalent mechanical element circuit for calculating the sound pressure contribution of the tweeter unit 31C. Fig. 27 is a diagram showing an equivalent mechanical element circuit for calculating the sound pressure contribution of the speaker unit 31B.

[0128] When creating a model of a single unit being driven from a model of multiple units being driven, including a network circuit, care must be taken when handling the electrical input terminal of the non-driven side, just as with parallel drive. In particular, since the electrical terminal short-circuit point, which corresponds to the constant voltage drive boundary condition, becomes the driving point of the network circuit, a model that reproduces the operation of a single unit must be modeled by adding the filter circuits of each network circuit to the equivalent mechanical element circuit of each unit.

[0129] Therefore, in this modified example, the tweeter and woofer are independently driven, and the equivalent mechanical element circuit is configured so that the filter circuit input electrical terminals of the non-driven units are short-circuited. Specifically, as shown in Figures 26 and 27, the computing device 100 removes connector 754 from equivalent mechanical element circuit 710B, connects connector 742 to high-pass filter relative acceleration proportional mass 704M, and connects connector 743 to low-pass filter coil equivalent spring 702M. The computing device 100 adds high-pass filter termination block 741C to the upper-stage equivalent mechanical element circuit to create equivalent mechanical element circuit 710BC for the high-pass filter and tweeter unit 31C. The computing device 100 adds low-pass filter termination block 741B to the lower-stage equivalent mechanical element circuit to create equivalent mechanical element circuit 710BB for the low-pass filter and speaker unit 31B. The computing device 100 sets boundary conditions for the high-pass filter terminal block 741C and the low-pass filter terminal block 741B, where the displacement is constrained to a predetermined displacement velocity by displacement constraints 759C and 759B. These displacement constraints 759C and 759B allow the configuration of a model that is passively short-circuited. In FIG. 26 , the computing device 100 applies a forced displacement velocity 760C to the high-pass filter terminal block 741C connected to the tweeter unit 31C, and calculates the sound pressure contribution of the tweeter unit 31C by setting or not setting the displacement velocity of the low-pass filter terminal block 741B to 0 (zero). In FIG. 27 , the computing device 100 applies a forced displacement velocity 760B to the low-pass filter terminal block 741B connected to the speaker unit 31B, and calculates the sound pressure contribution of the speaker unit 31B by setting or not setting the displacement velocity of the high-pass filter terminal block 741C to 0 (zero). That is, by setting the forced displacement velocity 760 corresponding to the drive voltage, and the forced displacement velocity 760C and the forced displacement velocity 760B to the same value, the calculation device 100 calculates the sound pressure of the two-way speaker system model by superimposing a model in which the tweeter is driven and the woofer is short-circuited and a model in which the tweeter is short-circuited and the woofer is driven.

[0130] Next, numerical calculation model data describing a calculation method according to a modified example will be described with reference to Figures 28, 29, 30, 31, 32, 33, and 34. Figures 28 and 31 are diagrams showing definitions of node names. Figures 29, 30, 32, 33, and 34 are diagrams showing examples of numerical calculation model data. Note that descriptions of data structures that are the same as those in Figures 9 and 10 will be omitted.

[0131] The names of each node are defined as shown in FIG. 28. Since the modified example will explain differences from the numerical calculation model data shown in FIGS. 9 and 10, only the necessary nodes are defined here. The displacement constraint 759 is defined as "GRID641," the connection point of the high-pass filter relative acceleration proportional mass 704M at the connector 754 is defined as "GRID1644," the low-pass filter coil equivalent spring 702M at the connector 754 is defined as "GRID2644," the low-pass filter relative acceleration proportional mass 701M is defined as "GRID701," the ground terminal 739B is defined as "GRID702," the ground terminal 49C is defined as "GRID1649," and the ground terminal 49B is defined as "GRID2649." The horizontal displacement in the direction of the forced displacement velocity 760 in FIG. 25 is defined as the X-axis, and the axis perpendicular to the X-axis in the two-dimensional plane of the equivalent mechanical element circuit 710B is defined as the Y-axis. These directional expressions are used for the convenience of explanation and are not intended to limit the orientation of the structure when actually used.

[0132] The numerical calculation model data DA3, DA4, DA5, DA6, and DA7 are in a data format that conforms to Nastran.

[0133] The numerical calculation model data DA3 is model data corresponding to the equivalent mechanical element circuit 710B shown in Fig. 25. The numerical calculation model data DA3 includes data D7A.

[0134] Data D7A is a data structure describing the processing content of step St202 of the placement step of a mechanical element circuit equivalent to the electric circuit in the flowchart shown in Figure 6. Data D7A defines the coordinates of GRID1644, GRID1649, GRID641, GRID2644, and GRID2649 as node definitions. Data D7A also defines, as "three-point X-displacement sharing," that the three end points (nodes 641, 1644, and 2644) share degrees of freedom so that they have the same X-displacement via connector 754 (see Figure 25).

[0135] The numerical calculation model data DA4 is model data corresponding to the equivalent mechanical element circuit 710B shown in Fig. 25. The numerical calculation model data DA4 includes data D8A, D9A, and D10A.

[0136] The data D8A has a data structure that describes the processing content of step St204 of the vibration displacement speed setting step in the flowchart shown in FIG.

[0137] Data D8A defines an end point for inputting a displacement velocity that excites the equivalent mechanical element circuit 710B. In data D8A, "SPC 30 1649 1 0.0" defines that the X degree of freedom of GRID 1649 (i.e., ground terminal 49C) is temporarily constrained to a displacement of 0 (zero). In data D8A, "SPC 30 2649 1 0.0" defines that the X degree of freedom of GRID 2649 (i.e., ground terminal 49B) is temporarily constrained to a displacement of 0 (zero). In data D8A, "SPC 30 641 1 0.0" defines that the X degree of freedom of GRID 641 (i.e., displacement constraint 759) is temporarily constrained to a displacement of 0 (zero). In this modification, a forced displacement constraint is defined by SPCD on the GRID 641 (i.e., displacement constraint 759) side. In data D8A, "SPCD 631 641 1 1.0" defines that either a forced displacement velocity or forced displacement acceleration is applied to GRID 641 (i.e., displacement constraint 759) at a value 1.0 times the set value. Thus, data D8A defines the position where the boundary condition for the displacement velocity is input.

[0138] Next, data D9A has a data structure that describes the processing content of step St205 of the vibration displacement speed setting step in the flowchart shown in FIG.

[0139] In data D9A, "RLOAD1 6641 631 0 0 1 VELO" defines a forced displacement in the X direction set in GRID 641 with identification number 631, i.e., SPCD 631. RLOAD1 defines a forced displacement in the X direction set in GRID 641 as a nodal load whose load type is VELO, i.e., forced displacement velocity, with reference to a table whose real part of the complex amplitude is defined by identification number 1, i.e., TABLED1 1, shown in FIG. 10, and whose imaginary part is 0, with both the initial time delay and initial phase set to 0 (zero). As described above, data D9A defines the boundary condition for the displacement velocity.

[0140] Next, data D10A has a data structure that describes the processing content of step St206 of the calculation execution step in the flowchart shown in FIG.

[0141] The data D10A unifies the boundary conditions and constraint conditions required for executing the calculation, and defines the method for executing the analytical calculation.

[0142] In data D10A, "DLOAD 612 1.0 1.0 6641" multiplies the external force defined by identification number 6641, i.e., RLOAD 6641, by an individual scale of 1.0, and combines it with other RLOADs to form a single result. Furthermore, DLOAD defines a load condition DLOAD 612 multiplied by an overall scale of 1.0. In this modified example, only one RLOAD is combined, but multiple RLOADs may be combined.

[0143] In data D10A, "MPCADD 620 621 622 23 24 25" combines the multi-point constraint MPCs defined by the identification numbers 621, 622, 23, 24, and 25, i.e., MPCs 621, 622, 23, 24, and 25, into one and defines it as a new MPCADD 620.

[0144] In data D10A, "SPCADD 607 30 35" combines the single-point constraint SPCs defined by identification numbers 30 and 35, i.e., SPCs 30 and 35, into one and defines it as SPCADD 7. In a modified example, SPC 35 includes an SPC defined in an SPC row (not shown) as a constraint condition that constrains all degrees of freedom other than translation in the X-axis direction at all nodes included in the equivalent mechanical element circuit 710B.

[0145] As described above, the numerical calculation model data DA3 and the numerical calculation model data DA4 describe the calculation method shown in the flowchart of Fig. 6 in the equivalent mechanical element circuit 710B shown in Fig. 25. By using the numerical calculation model data DA3 and the numerical calculation model data DA4, the calculation device 100 can analyze the sound pressure characteristics of the FEM model 724 in which the electric circuits in a two-way speaker system are converted into equivalent mechanical element circuits and integrated into one mechanical acoustic system.

[0146] Next, the names of the nodes in the FEM model in which the speaker unit 31B and the tweeter unit 31C are separated are defined with reference to Fig. 31. The displacement constraint 759C is defined as "GRID1654", and the displacement constraint 759B is defined as "GRID2654".

[0147] Next, with reference to Fig. 32, we will explain numerical calculation model data DA5 that can analyze the sound pressure characteristics of the equivalent mechanical element circuit for calculating the sound pressure contribution of the tweeter unit 31C shown in Fig. 26. In Fig. 32, only changes from the numerical calculation model data DA3 shown in Fig. 29 and the numerical calculation model data DA4 shown in Fig. 30 are described.

[0148] The numerical calculation model data DA5 includes data D7B and data D8B.

[0149] Data D7B is a data structure describing the processing content of step St202 of the placement step of a mechanical element circuit equivalent to an electric circuit in the flowchart shown in Figure 6. Data D7B defines the coordinates of GRID1654, GRID1649, GRID2654, and GRID2649 as node definitions. In data D7B, the computing device 100 deletes node 641 corresponding to the drive end point of connector 754.

[0150] The data D8B has a data structure that describes the processing content of step St204 of the vibration displacement speed setting step in the flowchart shown in FIG.

[0151] Data D8B defines an end point for inputting a displacement velocity that excites equivalent mechanical element circuit 710BC. In data D8B, "SPC 30 1649 1 0.0" defines that the X degree of freedom of GRID 1649 (i.e., ground terminal 49C) is temporarily constrained to a displacement of 0 (zero). In data D8B, "SPC 30 2649 1 0.0" defines that the X degree of freedom of GRID 2649 (i.e., ground terminal 49B) is temporarily constrained to a displacement of 0 (zero). In data D8B, "SPC 30 1654 1 0.0" defines that the X degree of freedom of GRID 1654 (i.e., displacement constraint 759C) is temporarily constrained to a displacement of 0 (zero). In data D8B, "SPC 30 2654 1 0.0" defines that the X degree of freedom of GRID 2654 (i.e., displacement constraint 759B) is temporarily constrained to a displacement of 0 (zero). In data D8B, a forced displacement constraint is defined by SPCD on the GRID 1654 (i.e., displacement constraint 759C) side. In data D8B, "SPCD 631 1654 1 1.0" defines that either a forced displacement velocity or a forced displacement acceleration is applied to GRID 1654 (i.e., displacement constraint 759C) at a value 1.0 times the set value. As described above, data D8B defines the position where the boundary condition for the displacement velocity is input. Also, although omitted in FIG. 30 because it is similar to data D9A in FIG. 29, RLOAD1 (not shown) sets the forced drive point of dynamic load 6641 to node 1654 of connector 54A.

[0152] Next, with reference to Fig. 33, a description will be given of numerical calculation model data DA6 that can analyze the sound pressure characteristics of the equivalent mechanical element circuit for calculating the sound pressure contribution of speaker unit 31B shown in Fig. 27. In Fig. 33, only changes from numerical calculation model data DA5 shown in Fig. 32 are described.

[0153] The numerical calculation model data DA6 includes data D8C.

[0154] The data D8C has a data structure that describes the processing content of step St204 of the vibration displacement speed setting step in the flowchart shown in FIG.

[0155] Data D8C defines a forced displacement constraint by SPCD on the GRID 2654 (i.e., displacement constraint 759B) side. In data D8C, "SPCD631 2654 1 1.0" defines that either a forced displacement velocity or a forced displacement acceleration is applied to GRID 2654 (i.e., displacement constraint 759B) at a value 1.0 times the set value. As described above, data D8C defines the position where the boundary condition for the displacement velocity is input. Also, although omitted in FIG. 33 because it is similar to data D9A in FIG. 30, RLOAD1 (not shown) sets the forced drive point of dynamic load 6641 to node 2654 of connector 54B.

[0156] Next, an example of a method of describing the relative acceleration proportional mass for low-pass filter 701M and the relative acceleration proportional mass for high-pass filter 704M in the numerical calculation model data will be described with reference to Fig. 34. The numerical calculation model data DA7 includes data D9.

[0157] The data D9 has a data structure that describes the processing content of step St202, which is a step of placing a mechanical element circuit equivalent to an electric circuit in the flowchart shown in Fig. 6. The data D9 defines the coordinates of each of GRID701 and GRID702 as the definition of a node.

[0158] The low-pass filter relative acceleration proportional mass 701M and the high-pass filter relative acceleration proportional mass 704M are described in a predetermined format in the numerical calculation model data, similar to spring elements and damper elements. For example, in numerical calculation model data conforming to Nastran, they are defined in the CMASS2 relative acceleration mass definition line shown in FIG. 34. The CMASS2 relative acceleration mass definition line includes, in the order described, a mass element definition declaration, a unique element identification number, the mass of the mass element, the node number of node 1, a component number in the displacement coordinate system that defines the displacement direction of node 1 specified in the CD entry of the GRID data, the node number of node 2, and a component number in the displacement coordinate system that defines the displacement direction of node 2 specified in the CD entry of the GRID data. Here, the CD entry represents the identification number of the coordinate system in which the displacement, degrees of freedom, constraints, and solution vectors are defined at the node. In data D7, the CMASS2 definition line is "CMASS2 71 3.0000-8 701 1 702 1", and a relative acceleration mass of "3.0000-8Ns" corresponding to a capacitor capacitance of 30 μF is provided between GRID 701 and GRID 702. ２ / mm (ton)." The mass value of the mass element 71 is input by converting a value in the N-kg-m unit system that is equal to the capacitance into a predetermined unit system.

[0159] In this modification, the mass proportional to relative acceleration is defined using the CMASS2 element, which can define the inertial force proportional to the relative acceleration between node 1 and node 2, but the definition of the mass proportional to relative acceleration is not limited to this. In particular, if the processing system for numerical calculation handles only the inertial force proportional to absolute displacement acceleration, it may use the equivalent mass proportional to relative acceleration expressed by a link mechanism using an equal lever and a mass proportional to absolute displacement acceleration of four times the mass described in Non-Patent Document 1.

[0160] (Summary of the Present Embodiment) The above description of the present embodiment discloses the following techniques.

[0161] <Technology 1> A calculation method according to this embodiment is a calculation method for calculating at least one of vibration and sound pressure generated in an electromechanical system of a speaker or actuator including an electromechanical energy converter having an electrical impedance Ze in a stationary state when a drive voltage is applied to the electromechanical energy converter, and includes: a first step of arranging in a virtual space an equivalent mechanical element circuit that is directly or indirectly connected to a point of application where a drive force generated in the electromechanical energy converter of a model in a virtual space acts, and that includes at least an electric impedance equivalent mechanical element having properties dynamically equivalent to the electric impedance Ze of the electromechanical energy converter; and a second step of setting, as a boundary condition, a displacement speed equivalent to the drive voltage applied to the electromechanical energy converter at any one of the endpoints of the equivalent mechanical element circuit or at a node that is indirectly connected to the endpoint and serves as an endpoint.

[0162] As a result, the calculation method according to this embodiment can replace an electromechanical energy converter including an electric circuit that needs to be coupled with a mechano-acoustic system with an equivalent mechanical element circuit including an electric impedance equivalent mechanical element having properties that are dynamically equivalent to the electric impedance of the electromechanical energy converter, and create an FEM model that can be directly integrated with the mechano-acoustic system. As a result, by using an FEM model that integrates the electromechanical energy converter with the mechano-acoustic system, the calculation method can calculate at least one of the vibration and sound pressure generated in the electromechanical system in a single large-scale calculation. In other words, the calculation method can reduce the load on the processor that executes the calculation process and shorten the time required for the calculation process.

[0163] <Technology 2> In the calculation method described in Technology 1, the electromechanical energy converter includes a voice coil having an electrical impedance Ze, and in a first step, the electrical impedance Ze of the voice coil is converted into an electrical impedance equivalent mechanical element having mechanically equivalent properties.

[0164] As a result, the calculation method according to this embodiment can replace the electromechanical energy converter, particularly one that uses a voice coil, with an equivalent mechanical element circuit including an electrical impedance equivalent mechanical element that has properties dynamically equivalent to the electrical impedance of the voice coil, and create an FEM model that can be directly integrated with the mechano-acoustic system. As a result, the calculation method can calculate at least one of the vibration and sound pressure generated in the electromechanical system with only one large-scale calculation, without performing separate calculations for the electromechanical energy converter that uses a voice coil and the mechano-acoustic system.

[0165] <Technology 3> In the calculation method according to Technology 1 or Technology 2, the electrical impedance equivalent mechanical element includes at least a mechanical resistance de calculated as de=1 / Re from Re, which is the DC resistance component of the electrical impedance Ze.

[0166] As a result, the calculation method according to the present embodiment can create a single FEM model by integrating a mechano-acoustic element that vibrates upon receiving an excitation force from an electromechanical energy converter and a mechanical element obtained by converting the electromechanical energy converter into a mechanical element, even for a model in which the electrical impedance Ze is simplified to only the DC resistance component Re. As a result, the calculation method can accurately calculate at least one of the vibration and sound pressure generated in an electromechanical system with only a single large-scale calculation.

[0167] <Technology 4> In the calculation method according to any one of Technology 1 to Technology 3, the boundary conditions set in the second step include a displacement constraint in which both primary side terminals of the equivalent mechanical element circuit are short-circuited to ground.

[0168] The FEM model created in this way accurately reproduces boundary conditions in which the output terminal of the voltage amplifier in the electric circuit is set to an internal resistance of 0 and is short-circuited to ground in passive AC operation. As a result, the calculation method according to this embodiment can accurately calculate at least one of the vibration and sound pressure generated in the electromechanical system with only one large-scale calculation.

[0169] <Technology 5> A calculation method according to any one of Technology 1 to Technology 4, which calculates at least one of vibration and sound pressure generated in an electromechanical system including a plurality of electromechanical energy converters, in which in a first step, an equivalent mechanical element circuit equivalent to each of the plurality of electromechanical energy converters is arranged, and an end point is further arranged by connecting a plurality of nodes that are indirectly connected to any end point or end point of each equivalent mechanical element circuit and serve as end points, and in a second step, a boundary condition is set at the end point connecting the plurality of nodes, with a displacement speed equivalent to a drive voltage as the boundary condition.

[0170] As a result, the calculation method according to this embodiment can calculate the total sound pressure of the reproduced sound of a speaker system including a plurality of speaker units in a single calculation.

[0171] <Technology 6> A calculation method according to Technology 4 for calculating at least one of vibration and sound pressure generated in an electromechanical system including a plurality of electromechanical energy converters, in which in a first step, a plurality of equivalent mechanical element circuits equivalent to each of the plurality of electromechanical energy converters are arranged, and a boundary condition that constrains a predetermined displacement speed is set at any end point of each equivalent mechanical element circuit or at all nodes that are indirectly connected to the end points and serve as end points, and in a second step, the boundary condition that is set is such that a predetermined non-zero displacement speed is set at any end point of one of the plurality of equivalent mechanical element circuits, and the displacement speeds input to the end points or nodes of the other equivalent mechanical element circuits are set to zero.

[0172] As a result, the calculation method according to this embodiment can calculate the sound pressure contribution of each speaker unit in a speaker system having multiple speaker units and calculate the total sound pressure of the speaker system using the principle of superposition, making it possible to easily calculate the complex mutual influence of the sound pressure transfer functions of a speaker system in which multiple speaker units are arranged.

[0173] <Technology 7> In the calculation method according to any one of Technology 1 to Technology 6, the equivalent mechanical element circuit further includes a mass element corresponding to a capacitor, which is an electrical component that constitutes a filter circuit connected to the outside of the electromechanical energy converter.

[0174] As a result, the calculation method according to this embodiment can easily calculate the sound pressure characteristics of a speaker system taking into account the influence of an analog filter configured as an electric circuit including a capacitor.

[0175] <Technology 8> In the numerical calculation model data described in any one of Technology 1 to Technology 7, the positional relationship and connection conditions of the mechanical elements of the equivalent mechanical element circuit, the boundary conditions of the displacement speed, and the elements for which the boundary conditions of the displacement speed are set are defined.

[0176] As a result, the numerical calculation model data according to this embodiment can specify that the electromechanical energy converter is converted into an equivalent mechanical element circuit, and that the mechanical acoustic system and the electrical circuit system are integrated into a single FEM model.

[0177] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, alterations, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also fall within the technical scope of the present disclosure. Furthermore, the components in the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0178] This application is based on a Japanese patent application filed on July 26, 2023 (Patent Application No. 2023-121720) and a Japanese patent application filed on September 8, 2023 (Patent Application No. 2023-146340), the contents of which are incorporated by reference into this application.

[0179] The techniques disclosed herein are useful as a calculation method and numerical calculation model data that reduce the calculation load of the vibration characteristics and sound pressure characteristics of an electromechanical system.

[0180] 10 Unit electrical circuit 10A, 10B, 200, 201, 610B, 610BA, 610BB, 710B, 710BB, 710BC Equivalent mechanical element circuit 11, 16, 17, 18, 19 Terminal 49, 49A, 49B, 49C, 739C, 739B Ground terminal 41, 41A, 41B, 741 End block 47, 48, 47A, 48A, 47B, 48B, 47C, 48C Driving force application end point 50, 51 Intermediate point 54, 56, 57 End point 59, 59A, 59B, 759, 759B, 759C Displacement constraint 60, 660, 660A, 660B, 760, 760B, 760C Forced displacement speed 12 Voltage amplifier 13 Voice coil DC resistance 14 Voice coil inductance 15 Electromechanical conversion virtual transformer 20, 20A, 20B, 20C Diaphragm 21 Magnetic circuit 23 Sound pressure observation point 30, 630, 730 Speaker system 31, 31A, 31B Speaker unit 32, 632, 732 Housing 34, 34A, 34B, 34C Center of gravity 35, 35A, 35B, 35C Center point 37, 637, 737, 739 Internal acoustic space 39, 639 External acoustic space 42, 42A, 42B, 45, 55, 754, 754B, 754C Connector 43, 52 Spring 44, 53 Damper 46 Lever 111 Electrical circuit 324, 624 FEM model 520, 620, 720 Structural model 521, 621, 721 Spatial model 522 Sound absorbing surface 523 Mechanism FEM model 31C Tweeter unit 616A, 616B, 619A, 619B, 716A, 716B, 719A, 719B Electrical terminal 701 Capacitor for low-pass filter 702 Coil for low-pass filter 703 Coil for high-pass filter 704 Capacitor for high-pass filter 790 Dividing network circuit 701M Mass proportional to relative acceleration for low-pass filter 702M Equivalent spring for low-pass filter coil 703M Equivalent spring for high-pass filter coil 704M Mass proportional to relative acceleration for high-pass filter 741B Low-pass filter terminal block 741C High-pass filter terminal block

Claims

1. A calculation method for calculating at least one of vibration and sound pressure generated in an electromechanical system of a speaker or actuator including an electromechanical energy converter having a stationary electrical impedance Ze when a drive voltage is applied to the electromechanical energy converter, the calculation method comprising: a first step of arranging in a virtual space an equivalent mechanical element circuit that is directly or indirectly connected to a point of application at which a drive force generated in the electromechanical energy converter of a model in a virtual space acts, and that includes at least an electrical impedance equivalent mechanical element having properties dynamically equivalent to the electrical impedance Ze of the electromechanical energy converter; and a second step of setting a displacement velocity equivalent to the drive voltage applied to the electromechanical energy converter as a boundary condition at any one of the end points of the equivalent mechanical element circuit or at a node that is indirectly connected to the end point and serves as an end point.

2. The calculation method according to claim 1, wherein the electromechanical energy converter includes a voice coil having an electrical impedance Ze, and in the first step, the electrical impedance Ze of the voice coil is converted into the electrical impedance equivalent mechanical element having mechanically equivalent properties.

3. The calculation method according to claim 1, wherein the electrical impedance equivalent mechanical element includes at least a mechanical resistance de calculated from Re, which is a direct current resistance component of the electrical impedance Ze, as de = 1 / Re.

4. The calculation method according to claim 1, wherein the boundary conditions set in the second step include a displacement constraint in which both primary terminals of the equivalent mechanical element circuit are short-circuited to ground.

5. A calculation method for calculating at least one of vibration and sound pressure generated in an electromechanical system including a plurality of said electromechanical energy converters, comprising: in said first step, arranging a plurality of said equivalent mechanical element circuits equivalent to each of said plurality of electromechanical energy converters; further arranging end points by connecting a plurality of nodes which are end points or which are indirectly connected to said end points of each of said equivalent mechanical element circuits; and setting a displacement velocity equivalent to said drive voltage as a boundary condition at the end point connecting the plurality of said nodes, as the boundary condition set in said second step.

6. A calculation method for calculating at least one of vibration and sound pressure generated in an electromechanical system including a plurality of said electromechanical energy converters, comprising: in said first step, arranging a plurality of said equivalent mechanical element circuits equivalent to each of said plurality of electromechanical energy converters; setting a boundary condition that is constrained to a predetermined displacement speed at any end point of each of said equivalent mechanical element circuits or at all nodes that are indirectly connected to said end points and serve as end points; and in said second step, setting the boundary condition to a predetermined non-zero displacement speed at any end point of one of said plurality of equivalent mechanical element circuits, and setting the displacement speeds input to the end points or nodes of the other equivalent mechanical element circuits to zero.

7. The calculation method according to claim 1, wherein the equivalent mechanical element circuit further includes a mass element corresponding to a capacitor that is an electrical component constituting a filter circuit connected externally to the electromechanical energy converter.

8. Numerical calculation model data describing at least the calculation method according to any one of claims 1 to 7, which defines the positional relationship and connection conditions of components of the equivalent mechanical element circuit, the boundary conditions of the displacement velocity, and the elements to which the boundary conditions of the displacement velocity are set.

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