JP6917937B2 - Evaluation method and evaluation device for sound field simulation by active noise control - Google Patents

Description

The present invention is an active noise control capable of efficiently examining a large number of layout proposals at once based on the superiority or inferiority of the noise reduction effect with respect to the installation position layout of the control speaker and the control microphone used for the active noise control. The present invention relates to an evaluation method and an evaluation device for sound field simulation.

Patent Documents 1 to 3 are known as techniques for reducing noise from a noise source. The "silencer" of Patent Document 1 is provided with two muffling speakers in order to create a muffling area in a specific range by overlapping emitted sounds, and is provided with two sensor microphones corresponding to each muffling speaker. , It is a means of connecting an oscillator that freely sets the frequency range of the noise to be eliminated to the active controller.

The "plant monitoring and control system" of Patent Document 2 is a means for transmitting individual information to an operator in a waiting state by using a sound output method, which is an effective information propagation means for propagating an accidental event, without attaching a receiver. The voice output device is a speaker that outputs control information (fault, abnormality transmission), a unidirectional speaker for muffling, a microphone for sound pressure detection, and a sensor that acquires plant (abnormality) information. , And an active sound field control unit.

The "method for determining the position of noise detecting means in a muffling system" of Patent Document 3 is a second noise in which ANC technology can be fully utilized to satisfactorily mute noise generated from a noise source arranged in a three-dimensional closed space. With the task of obtaining a method for determining the position of the detection means, in order to apply the ANC technology in a three-dimensional closed space such as a basement, a plurality of high sound pressure level frequencies having a high level of noise generated from a noise source are obtained, and the plurality of them are obtained. For each sound with a high sound pressure level frequency, wave acoustic analysis is performed in the three-dimensional closed space to estimate the acoustic state of the three-dimensional closed space, and the sound pressure level in the three-dimensional closed space is determined at the abdomen of the standing wave. A position higher than the average sound pressure level in the space is set as the second position where the second noise detecting means is arranged.

Japanese Unexamined Patent Publication No. 9-160566 Japanese Unexamined Patent Publication No. 10-27003 Japanese Unexamined Patent Publication No. 2011-107673

For example, although various noises are present in a factory, it is often impossible to take measures such as surrounding the noise source with a sound insulation wall or the like, which is a usual noise countermeasure, because it is necessary to visually check the production status. Therefore, there is a demand to reduce the noise in the area where workers are present without using a sound insulation wall or the like. Active noise control (hereinafter referred to as ANC), which is one of the noise countermeasure methods, can reduce noise in a certain area without obstructing the field of view. The ANC uses the control microphone position as the position where the worker is located, and in order to reduce the target sound (noise) at this control microphone position, the ANC is a speaker for controlling a sound having the same amplitude and opposite phase as the target sound. It is a method to output from.

In ANC, when a control speaker is arranged in the vicinity of a noise source, for example, as a countermeasure for engine noise of heavy construction machinery, a large noise reduction effect can be obtained with one control speaker and one control microphone. However, as shown in FIG. 4, when the control speaker b is arranged at a position away from the noise source a, in order to reduce the noise of the entire area such as the area where the worker c is present, a large number of control speakers are used. And a control microphone is required, which is difficult to realize.

In this way, when installing the ANC system in the actual field, the characteristics of one or more control speakers and the placement positions of these control speakers and control microphones are selected many times. It has to be repeated many times, and it is not always possible to obtain a sufficient noise reduction effect, and there is a problem that it is extremely difficult.

In Japanese Patent Application No. 2018-006542, the applicant of the present application can verify the noise reduction effect by simulation, such as before installing the system at the site, etc., when the control speaker is arranged at a position away from the noise source. We proposed a simulation method and a simulation device for a sound field with possible active noise control, and solved the above problems.

Considering the simulation method and simulation device disclosed in this patent application as an example, in the field where a control speaker and a control microphone are actually installed, for example, in a factory, pillars, walls, ceilings, etc. There are situations in which various machines, devices, piping lines, and other equipment are already installed, and various machines and devices cannot be easily moved, even if they are not limited to the factory.

Keeping in mind the restrictions on the layout of these control speakers, which is a problem when installing control speakers and control microphones in such a site, a large number of layout proposals are made at once based on the superiority or inferiority of the noise reduction effect. If it is possible to study efficiently, the control speaker and the control microphone can be optimally laid out, and it has been desired to devise such a measure.

The present invention has been devised in view of the above-mentioned conventional problems, and is based on the superiority or inferiority of the noise reduction effect of a large number of layout proposals for the installation position layout of the control speaker and the control microphone used for the ANC. It is an object of the present invention to provide an evaluation method and an evaluation device for a sound field simulation by active noise control, which can be examined efficiently.

The evaluation method of the sound field simulation by the active noise control according to the present invention is the position coordinates of a virtual noise source that emits noise for simulating the noise reduction effect, the data of the noise, and the virtual control speaker that emits the control sound. Position coordinates, position coordinates of a virtual control microphone that receives sound propagated from both the noise source and the control speaker, and position coordinates of a plurality of evaluation points set in a target area for evaluating the noise reduction effect. The arithmetic unit that receives the input of the control sound calculates the control sound data that can reduce the noise by satisfying the sound pressure reduction condition at the position coordinates of the control microphone, and the calculated control sound data and the noise. This is a sound field simulation method by active noise control that calculates and outputs the noise reduction effect value at the position coordinates of each evaluation point from the data of The input of the target average value with respect to the average value obtained by averaging the noise reduction effect values at each of the plurality of evaluation points, and the combination of the position coordinates of any one of the control speakers and the position coordinates of any one of the control microphones. The first step of accepting a plurality of inputs of the calculation position coordinate set consisting of the above is executed; then, the above simulation is executed for each of the above calculation position coordinate sets, and the plurality of the above evaluations of the target area are performed. The noise reduction effect values at each position coordinate of the point are calculated, and the average value obtained by averaging the calculated noise reduction effect values within the target area is calculated for each of the plurality of position coordinate sets for calculation. The second step of calculating the plurality of the average values is repeatedly executed; and then, among the plurality of the above-mentioned average values, the position coordinate set for candidate calculation in which the average value equal to or more than the above-mentioned target average value is calculated is obtained. From the extracted and extracted position coordinate sets for candidate calculation, the position coordinate set for satisfaction calculation that matches the preset selection criteria is extracted, and the position of the control speaker of the extracted position coordinate set for satisfaction calculation is extracted. It is characterized in that the third step of outputting the coordinates and the position coordinates of the control microphone as a determination value is executed.

In the arithmetic unit, the position of the target area can be updated to another position by changing the position coordinates of the evaluation point, and the position of the evaluation point can be updated to another position by changing the position coordinates. It is characterized in that it can be updated to a position, the target average value can be updated to another target average value, and the calculation position coordinate set can be updated to another calculation position coordinate set.

When all of the plurality of average values are not equal to or more than the target average value, the arithmetic unit updates the position of the target area, updates the position of the evaluation point, updates the target average value, and sets the position coordinates for calculation. It is characterized in that at least one of the updates is performed and the first to third steps are executed.

The evaluation device for sound field simulation by active noise control according to the present invention is characterized by including the above-mentioned arithmetic unit.

In the evaluation method and evaluation device for sound field simulation by active noise control according to the present invention, a large number of layout proposals are made at once for the installation position layout of the control speaker and the control microphone used for ANC, and the noise reduction effect is achieved. It can be examined efficiently based on the superiority or inferiority of.

It is a flowchart which shows the procedure of one preferable embodiment of the evaluation method of the sound field simulation by the active noise control which concerns on this invention. It is explanatory drawing which shows the structure of one preferable embodiment of the evaluation apparatus of the sound field simulation by the active noise control which concerns on this invention. It is explanatory drawing explaining the evaluation method of the sound field simulation by the active noise control shown in FIGS. 1 and 2 and an example of the sound field simulation applicable to the evaluation apparatus. It is explanatory drawing explaining a mode that active noise control is performed by a control speaker arranged at a position away from a noise source.

Hereinafter, a preferred embodiment of the evaluation method and the evaluation device for the sound field simulation by the active noise control according to the present invention will be described in detail with reference to the accompanying drawings.

The evaluation method and evaluation device for sound field simulation by active noise control according to the present invention include the position coordinates of a virtual noise source that emits noise for simulating the noise reduction effect, and the position coordinates of a virtual control speaker that emits control sound. , Position coordinates of a virtual control microphone that receives sound propagated from both the noise source and the control speaker, each position coordinate of a plurality of evaluation points set in the target area for evaluating the noise reduction effect, and noise data. It is assumed that a simulation method is executed using and a simulation device that executes such processing.

Then, the arithmetic unit that accepts the input of the above position coordinates and noise data calculates the control sound data that can reduce the noise by satisfying the sound pressure reduction condition in the position coordinates of the control microphone, and the calculated control sound. From the data and noise data, the noise reduction effect value at the position coordinates of each evaluation point is calculated and output for simulation. An example of the simulation will be described later.

As shown in FIG. 2, a conventionally well-known input device 2 and an output device 3 are connected to the arithmetic unit 1 that performs the simulation, the following calculation is performed based on the input value input from the input device 2, and the calculation result is output. It is designed to output from the device 3.

In the present invention, the position coordinates of the noise source and the noise data are treated as fixed data, and the position coordinates of the control speaker and the control microphone are treated as a plurality of primary data by setting various position coordinates. , Each of a plurality of primary data is individually simulated so that the position coordinates (layout) of the control speaker and control microphone can be efficiently and optimally determined in relation to the noise reduction effect. Is.

In case the sufficient noise reduction effect cannot be obtained with the set multiple primary data, the position coordinates of the target area and the evaluation point are set as secondary data that set different position coordinates, and the secondary data is changed.・ After updating, simulations are performed so that the optimal layout of control speakers and control microphones can be determined efficiently.

In particular, in the present invention, regarding the position coordinates of the control speaker and the control microphone, the position coordinates of any one of the control speakers and the position coordinates of any one of the control microphones are combined, and the combination of the position coordinates is used. , A position coordinate set for calculation related to a control speaker and a control microphone, and a plurality of the position coordinate sets for calculation are input to the calculation unit 1 at once, and the calculation unit 1 is individually used for each position coordinate set for calculation. It is designed to perform simulations.

FIG. 1 shows a procedure of an evaluation method executed by an evaluation device for sound field simulation by ANC according to the present invention.

First, the first step is executed. The target area for evaluating the noise reduction effect (the area where the workers explained in the background technology are) and the positions (position coordinates) of a plurality of evaluation points within the target area for individually calculating the noise reduction effect value. ) And set. The arithmetic unit 1 receives input of the position coordinates of these evaluation points from the input device 2.

Further, the arithmetic unit 1 receives input of a target average value set from the input device 2 with respect to the average value obtained by averaging the noise reduction effect values at each of the plurality of evaluation points.

As will be described later, if the average value obtained by averaging the noise reduction effect values of each evaluation point is equal to or higher than the set target average value, the installation position layout of the control speaker and the control microphone is adopted as a candidate layout. , If it is less than the target average value, it will not be adopted.

At the same time, various positions (position coordinates) where the control speaker and the control microphone can be installed are set in light of the site, and one of the control speakers is set with respect to these installable positions such as the control speaker. Determine a plurality of calculation position coordinate sets consisting of a combination of one position coordinate and any one position coordinate of the control microphone (in FIG. 1, i = 1 to N; N is the number of calculation position coordinate sets). do. The arithmetic unit 1 receives input of these plurality of arithmetic position coordinate sets from the input device 2.

Next, the second step is executed. The arithmetic unit 1 executes a simulation individually for each arithmetic position coordinate set. As a result, the arithmetic unit 1 calculates the noise reduction effect value at each position coordinate of the plurality of evaluation points of the target area in the arithmetic position coordinate set.

Further, the arithmetic unit 1 calculates an average value obtained by averaging the calculated noise reduction effect values in the target area with respect to the arithmetic position coordinate set.

In the second step, the simulation is repeated for each of the plurality of calculation position coordinate sets, and the average value is calculated for each calculation position coordinate set. Therefore, in the second step, a plurality of average values corresponding to each of the plurality of arithmetic position coordinate sets are calculated.

Next, the third step is executed. In the third step, the arithmetic unit 1 first selects an arithmetic position coordinate set for which an average value equal to or greater than the target average value is calculated among a plurality of average values calculated for each arithmetic position coordinate set. , It is extracted as a candidate calculation position coordinate set that is a candidate for the layout of the control speaker and the control microphone that are finally determined.

The arithmetic unit 1 further extracts a position coordinate set for sufficiency calculation that matches a preset selection criterion from the position coordinate set for candidate calculation.

The selection criteria are, for example, (1) the maximum average value, (2) the minimum standard deviation of the noise reduction effect value at each evaluation point in the target area, and (3) the noise reduction effect at the selected evaluation point in the target area. The maximum value, etc. can be mentioned. The selection criterion is adopted to extract any one from a plurality of candidate calculation position coordinate sets. Whether or not these selection criteria are satisfied is determined by the arithmetic unit 1 based on the arithmetic expression stored in the arithmetic unit 1.

As the evaluation based on the selection criteria, not only the best one is selected, but also the ranking in each selection criterion may be obtained, or each selection criterion may be weighted and evaluated by a plurality of selection criteria. ..

The arithmetic unit 1 outputs the control speaker position coordinates and the control microphone position coordinates of the extracted sufficiency calculation position coordinate set as determination values from the output device 3.

In this way, for the control speaker and control microphone that need to be examined for the layout of the installation position, by repeating the simulation with a plurality of calculation position coordinate sets, a large number of layout proposals can be considered at once, and the noise reduction effect is superior or inferior. It is possible to efficiently study based on the above, and to evaluate the sound field simulation by ANC.

In particular, paying attention to the position coordinates of the control speaker and the control microphone, which may be restricted in the installation position, the arithmetic unit 1 is made to execute the arithmetic processing by the arithmetic position coordinate set set by the combination of these. Therefore, compared to the case where the position coordinates of the control speaker and the control microphone are handled individually and the calculation processing is performed, or the position coordinates of the evaluation points are also included in the set and the calculation processing is performed, these control speakers and control are performed. It is possible to efficiently cause the calculator 1 to execute the position coordinates of the microphone, that is, the process of appropriately evaluating the suitability of these layouts in a short time.

As a result, the control speaker and the control microphone can be installed in the field in an optimum layout while exerting a desirable noise reduction effect. Further, since the evaluation can be performed only by the calculation by the arithmetic unit 1, the layout can be easily examined and evaluated anytime and anywhere.

Among the input values that the arithmetic unit 1 accepts the input, the position coordinates of the noise source and the noise data are fixed data.

On the other hand, the position of the target area can be updated to another position by changing the position coordinates of the evaluation points, and the position of each evaluation point can be updated to another position by changing the position coordinates individually. It is possible, the target average value can be updated to another target average value, the calculation position coordinate set can be updated to another calculation position coordinate set, and each time the calculation unit 1 updates these. It is designed to accept data input.

Further, in the execution process of the third step, when all of the plurality of average values of the target area calculated in each simulation are not equal to or more than the target average value, the process returns to the first step, the position of the target area is updated, and the position of the evaluation point is changed. At least one of the update, the update of the target average value, and the update of the position coordinate set for calculation is performed, the calculator 1 accepts the input of the update data, and the first step to the third step are executed again.

As a result, for example, the control speaker and the control microphone are subjected to a re-evaluation from a viewpoint different from the processing result immediately before the candidate calculation position coordinate set could not be extracted, and the control speaker and the control microphone are exhibited with the desired noise reduction effect. It can be installed in the field with the optimum layout.

<< An example of sound field simulation by ANC >>
This simulation makes it possible to verify the noise reduction effect when the control speakers are placed at a distance from the noise source instead of near the noise source in ANC targeting a part of the open space. By taking into account the predominant frequency and propagation direction of noise in the target area, it is possible to efficiently arrange control speakers and select an appropriate directivity, effectively with a small amount of equipment. Make it possible to reduce noise.

Specifically, when applying ANC to an actual space such as a factory, the position and propagation direction of the noise source and the frequency of the noise to be reduced can be limited. Therefore, by arranging the optimum control speakers for reducing noise and setting the optimum speaker radiation angle, even if the number of these control speakers and control microphones is several or single, the noise in the target area Can be effectively reduced.

This simulation is a prediction method based on the concept of wave field synthesis (superposition of waves) for the noise reduction effect considering the arrangement of control speakers and their directivity. In addition, the sound field due to noise can be represented by a plurality of evaluation points evenly arranged in the region, and the range in which the noise reduction effect can be obtained can be predicted by combining with the sound field due to the control sound from the control speaker. To do so.

In one example of this simulation, the arrangement of control speakers and their directivity can be evaluated when noise propagates from one direction to the target area.

FIG. 3 shows an explanatory diagram illustrating the concept of this simulation. The simulation is executed inside the arithmetic unit 1 using various set data, and the simulation result is acquired in the arithmetic unit 1.

In the arithmetic unit 1 that executes the simulation, with respect to the noise source N, the position coordinates N (hereinafter, simply referred to as “noise source”) of the virtual noise source (hereinafter, simply referred to as “noise source”) in the two-dimensional plane orthogonal coordinate system (XY orthogonal coordinate system) are used. xN, yN) and noise data emitted from the noise source N in order to simulate the noise reduction effect are input from the input device 2.

For the noise data propagated from the noise source N, sound data appropriately selected may be used in the experimental implementation, while observation in the space is observed in the simulation when ANC is applied to the actual space. The sound data obtained in advance may be used. The noise data propagated from the noise source N may be measured at any position within the target area, and may be acquired in advance before performing the simulation, such as on a desk or the like. It is preferable to input the data to the arithmetic unit 1 of the above and perform the simulation. The noise data includes, for example, the (sound) intensity (volume velocity) Q0 of the noise source N, the wave number κ, the angular frequency ω, the period T, and the like.

The arithmetic unit 1 has the control speaker S, the position coordinates S (xS, yS) of the virtual control speaker (hereinafter, simply referred to as “control speaker”) in the two-dimensional plane orthogonal coordinate system, and noise reduction. The control sound data for this is input.

In this simulation, in particular, the control speaker S is positioned not in the vicinity of the noise source N but at a position separated from the noise source N and as a selectably set position as the simulation position.

As the control sound data, various sound data can be used in order to obtain the noise reduction effect. The sound data of the control sound includes, for example, a coefficient α representing the strength of the sound source of the control speaker S with respect to the noise source N, and the position of the control speaker S (control sound from) with respect to the noise source N (noise from). There is a phase difference φ etc.

The arithmetic unit 1 has a control microphone P that is used in an actual ANC and receives sound (noise and control sound) propagated from both the noise source N and the control speaker S in a two-dimensional plane orthogonal coordinate system. The position coordinates P (xP, yP) of the virtual control microphone (hereinafter, simply referred to as “control microphone”) are input.

The control microphone P is positioned as a simulation position at a position that can be selectably set on condition that the control microphone P is within a region within both the directivity angle of the noise emitted from the noise source N and the directivity angle of the control speaker S. ..

Further, in order to evaluate the noise reduction effect, the position of the evaluation point J indicating the reached sound pressure is input and set in the arithmetic unit 1 as the position coordinates J (xJ, yJ) in the two-dimensional plane orthogonal coordinate system. NS. The position coordinates J (xJ, yJ) of the evaluation point J correspond to information on the noise control position, for example, the position where the worker is required to reduce the noise as described above, and are in the two-dimensional plane orthogonal coordinate system. Set to be selectable.

In this simulation, in short, the noise source N, the control speaker S, the control microphone P, and the evaluation point J are arranged on the same two-dimensional plane Cartesian coordinate system, and the sound propagating in the plane by the arithmetic unit 1 Simulation result is acquired.

Further, in this simulation, the evaluation point J is set at the center position of a plurality of square areas in which the area to be simulated (hereinafter, simply referred to as “target area”) is divided by a grid. The simulation result by the arithmetic unit 1 is calculated for a plurality of evaluation points J, acquired in the form of sound pressure distribution in the target area, and output to an output device 3 such as a monitor or a printer. It is composed.

The calculator 1 simulates predicting the effect of ANC by superimposing the sound propagating from the noise source N and the sound propagating from the control speaker S at the evaluation points J provided at equal intervals in the target area. Execute.

The arithmetic unit 1 has input noise source N, control speaker S, control microphone P, and position coordinates N (xN, yN), S (xS, yS), P (xP, yP) of the evaluation point J. From J (xJ, yJ), various numerical values shown in FIG. 3, specifically, the length of the first line segment (rNS) between the noise source N and the control speaker S, the noise source N, and the control. The length of the second line segment between the microphones P (rNP), the length of the third line segment between the control speaker S and the control microphone P (rSP), the fourth line between the noise source N and the evaluation point J. Minute length (rNJ), length of 5th line segment between control speaker S and evaluation point J (rSJ), length of 6th line segment between control microphone P and evaluation point J (rPJ), The first angle (θ1) formed by the second line segment and the fourth line segment, the second angle (θ2) formed by the third line segment and the fifth line segment, and the third angle formed by the second line segment and the sixth line segment. It is configured to calculate (θα) and the fourth angle (θβ) formed by the third line segment and the sixth line segment.

The effect simulated and predicted by the arithmetic unit 1 is obtained according to the following logic.

(A) At the position coordinates P (xP, yP) of the control microphone, the velocity potentials δN, δS of the sound propagating from the noise source N and the control speaker S and arriving at the control microphone P are given by the equations (1) and δS. It is assumed that the equation (2) is obtained.

For the arithmetic unit 1, the noise from the noise source N is a sinusoidal wave, and the first angle θ1 and the second angle θ2 are larger than the directional angle of the noise source N and the directional angle of the control speaker S. When it is large, the amplitude of the sound from the noise source N and the control speaker P at the evaluation point J is attenuated, and the attenuation characteristic of the amplitude depends on the directional characteristics of the noise source N and the control speaker S. The value (measured value or specification data) is set.

(B) From the relationship between the velocity potential and the sound pressure, when the above equations (1) and (2) are differentiated with respect to time t and multiplied by the air density ρ0, the noise source N and the noise source N represented by the following equations (3) and (4) are obtained. The sound pressures of the control speaker S are PN and PS.

(C) At the position coordinates P (xP, yP) of the control microphone, when the amplitude ratio of the noise from the noise source N and the control sound from the control speaker S is 1, and the phase difference is π, the noise is canceled. The sound pressure at the position coordinates P (xP, yP) of the control microphone is reduced. When the sound pressure conditions of the sound propagating sound (noise) from the noise source N and the sound propagating sound (control sound) from the control speaker S at the position coordinates P (xP, yP) of the control microphone at this time are obtained, the amplitude is obtained. Regarding the ratio, from the ratio of the parts related to the amplitude of equations (1) and (2),

Since the amplitude ratio Ar = 1 at the position coordinates P (xP, yP) of the control microphone,

Therefore, a coefficient α representing the sound source strength of the control speaker S with respect to the sound source strength of the noise source N is set.

(D) Subsequently, the phase difference φ is determined from the phases of the equations (3) and (4).

Since the phase difference Δφ = π at the position coordinates P (xP, yP) of the control microphone,

Is required.

(E) The effect of ANC in the target area is the distance between the noise source N and each evaluation point J (length of the fourth line segment; rNJ) and the distance between the control speaker S and each evaluation point J (line 5). Since it is calculated by the length of a minute; rSJ), the distance between the noise source N and the control microphone P (the length of the second line segment; rNP) and the control speaker S in each of the equations (6) and (8). By substituting the length rNJ of the fourth line segment and the length rSJ of the fifth line segment into the distances of the control microphones P (the length of the third line segment; rSP) as numerical values, the amplitude ratio at each evaluation point J AJ and the phase difference ΔφJ are obtained by the following equations (5) and (7).

(F) The distances (rNJ, rSJ) between each of the noise source N and the control speaker S and each evaluation point J can be obtained as follows, although they are out of the description of the procedure. In addition to the length rNP of the second line segment between the noise source N and the control microphone P and the length rSP of the third line segment between the control speaker S and the control microphone P described above, the control microphone P and the evaluation The length rPJ of the 6th line segment between the points J, the 3rd angle (θα) formed by the 2nd line segment and the 6th line segment, and the 4th angle (θβ) formed by the 3rd line segment and the 6th line segment. From the cosine theorem,

Is required.

(G) Next, considering the effect of ANC at each evaluation point J as the following equation (11),

“D” and “C” in the equation (11) are the following equations (12) and (13) using the amplitude ratio Aj and the phase difference Δφj at the position coordinates J (xJ, yJ) of the evaluation points. Can be represented.

By expressing the amplitude of "C" as the unit amplitude of "D" and the amplitude ratio Aj at the evaluation point J, the noise (propagated sound) from the noise source N and the control sound (propagated sound) from the control speaker S ( Expresses the amplitude ratio of (propagated sound). As a result, the following equation (14) is obtained.

Here, since the latter half of the second term of the equation (14) is an effective value of a sine wave having a unit amplitude, the following equation (15) is obtained.

By evaluating the effect (noise reduction effect value) at the position coordinates J (xJ, yJ) of the evaluation point whose sound pressure is controlled by ANC according to the above equation (15), the noise source N and the control speaker are evaluated. The effect of ANC at the evaluation point J can be predicted from the positional relationship between the position coordinates N (xN, yN), S (xS, yS), P (xP, yP) of S and the control microphone P and the target area, respectively. Possible simulation results can be obtained.

The effect E obtained by the formula (15) is sound pressure, and the unit is Pa (Pascal). By applying the following formula (16), it can be converted into dB units.

Equations (9) to (15) assume a two-dimensional space as described above. For example, in the case of a factory with a high ceiling, the noise source N, the control speaker S, the control microphone P, and the evaluation point J are set to have the same height, so that the simulation is performed assuming a two-dimensional space. be able to. On the other hand, for example, when the noise source N is on the second floor and the evaluation point J is on the first floor, a two-dimensional space of an oblique vertical plane including these two points can be set in the same manner. Simulation can be performed.

In this simulation, it is an ANC that targets a part of the open space, and when the control speaker S is placed at a position away from the noise source N, before the system is installed at the site, etc. , The noise reduction effect can be verified by simulation.

In particular, as long as there is sound data of the noise source N, the simulation is performed by the arithmetic processing by the arithmetic unit 1 only by inputting the position where the control speaker S and the control microphone P can be installed in the actual space. be able to. Therefore, not only can the arithmetic unit 1 be brought into the actual space where noise is measured and the simulation can be performed, but also the simulation can be performed on a desk or the like even if it is not in the field.

Specifically, in the arithmetic unit 1, the position coordinates of the control speaker S and the control microphone P can be freely moved, and the control sound and the directional angle of the control speaker S can be arbitrarily changed to evaluate the evaluation point J. The simulation result of the effect of ANC in the above can be acquired, and the result of movement or change can be easily and quickly acquired and evaluated.

Then, by acquiring the simulation results, when installing the ANC system at the actual site, the characteristics of one or more control speakers can be selected, and the positions of these control speakers and control microphones can be arranged. It is possible to eliminate the need for the work of repeating the selection process over and over again, and it is possible to efficiently design and install the ANC system suitable for the actual condition of the installation location.

1 Arithmetic 2 Input device 3 Output device a Noise source b Control speaker c Worker

Claims (4)

Propagated from both the position coordinates of the virtual noise source that emits noise and the data of the noise for simulating the noise reduction effect, the position coordinates of the virtual control speaker that emits the control sound, the noise source, and the control speaker. The arithmetic unit that accepts the input of the position coordinates of the virtual control microphone that receives the sound and the position coordinates of each of the plurality of evaluation points set in the target area for evaluating the noise reduction effect is the position coordinates of the control microphone. The data of the control sound capable of reducing the noise by satisfying the sound pressure reduction condition is calculated, and the noise reduction effect value at the position coordinates of the evaluation points is calculated from the calculated control sound data and the noise data. This is a sound field simulation method using active noise control that calculates and outputs
The above arithmetic unit
First, the input of the target average value with respect to the average value obtained by averaging the noise reduction effect values at each of the plurality of evaluation points in the target area, the position coordinates of any one of the control speakers, and the control microphone. Execute the first step of accepting a plurality of inputs of a position coordinate set for calculation consisting of a combination of one position coordinate.
Next, the simulation is executed for each of the calculation position coordinate sets, the noise reduction effect values at each position coordinate of the plurality of evaluation points in the target area are calculated, and these noise reduction effect values are calculated. The calculation of the average value obtained by averaging the above average values in the target area is repeated for each of the plurality of position coordinate sets for calculation, and the second step of calculating the plurality of the average values is executed.
After that, from these plurality of average values, a candidate calculation position coordinate set for which the average value equal to or higher than the target average value is calculated is extracted, and the extracted candidate calculation position coordinate set is preset. A third position coordinate set for sufficiency calculation that matches the selected selection criteria is extracted, and the position coordinates of the control speaker and the position coordinates of the control microphone of the extracted position coordinate set for sufficiency calculation are output as determination values. An evaluation method for sound field simulation with active noise control, characterized by performing steps. In the arithmetic unit, the position of the target area can be updated to another position by changing the position coordinates of the evaluation point, and the position of the evaluation point can be updated to another position by changing the position coordinates. The first aspect of the present invention is that the target average value can be updated to a position, the target average value can be updated to another target average value, and the calculation position coordinate set can be updated to another calculation position coordinate set. Evaluation method of sound field simulation by active noise control described in. When all of the plurality of average values are not equal to or more than the target average value, the arithmetic unit updates the position of the target area, updates the position of the evaluation point, updates the target average value, and sets the position coordinates for calculation. The method for evaluating a sound field simulation by active noise control according to claim 2, wherein at least one of the updates is performed and the first to third steps are executed. An evaluation device for sound field simulation by active noise control, which comprises the arithmetic unit according to any one of claims 1 to 3.

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