Display method of sound source survey result

Abstract

To clearly display a sound source location of noise generated on a treading side and a kicking side as a tire rotates, and a sound intensity distribution at the sound source location.SOLUTION: A method for displaying sound source survey results of the present invention performs an acoustic analysis by using a road surface model and a tire model, and obtains a frequency response function of sound from a model sound source point to a model measurement point. The sound generated when an actual tire is rolled is measured from a treading side and a kicking side by microphones arranged at a plurality of measurement points, and the sound intensity on the treading side at the model sound source point is calculated based on the sound measured from the kicking side and a frequency response function, and the sound intensity on the treading side at the model sound source point is calculated based on the sound measured from the kicking side and a frequency response function. A ground contact surface of the tire model is displayed, and indications are provided on one and the other sides of the ground contact surface in a tire circumferential direction according to the sound intensities on the treading side and the kicking side at the model sound source point.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a method for displaying a result of sound source localization. [Background technology]

[0002] Various methods have been proposed for identifying the source position of noise generated from a rotating tire (see, for example, Patent Documents 1 and 2 listed below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5089253 [Patent Document 2] Patent Publication No. 2022-102035 Summary of the Invention [Problem to be solved by the invention]

[0004] The sound source position and the sound intensity distribution at the sound source position differ between the leading side and trailing side of the tire, but conventional methods cannot display this difference in an easily understandable manner.

[0005] The present invention has been made in consideration of the above circumstances, and has an object to propose a method for displaying sound source exploration results that can clearly display the sound source positions of noise generated on the leading-in and trailing-out sides as the tire rotates, and the sound intensity distribution at the sound source positions. [Means for solving the problem]

[0006] The present invention includes the embodiments set forth below.

[0007] [1] A method for measuring a sound generated when an actual tire is rolled, comprising: a first step of setting a plurality of actual measurement points at positions where a microphone is used to measure the sound generated when an actual tire is rolled; a second step of setting a road surface model, a tire model that contacts the road surface model, and an acoustic space model around the tire; a third step of setting a plurality of model sound source points on one side of the tire circumferential direction of the tire on the contact surface of the tire model; a fourth step of setting a plurality of model measurement points at positions corresponding to the plurality of actual measurement points; a fifth step of performing acoustic analysis using the road surface model and the tire model to obtain a frequency response function of the sound from the model sound source points to the model measurement points; and a fifth step of measuring the sound generated when an actual tire is rolled from the leading side with the microphones arranged at the plurality of actual measurement points. a sixth step of determining a sound intensity distribution on the leading-in side and the sound intensity on the leading-in side at the model sound source point based on the actually measured sound and the frequency response function; a seventh step of measuring sound generated when an actual tire is rolling from the trailing-in side with the microphones arranged at a plurality of the actually measured points, and determining a sound intensity distribution on the trailing-in side and the sound intensity on the trailing-in side at the model sound source point based on the actually measured sound and the frequency response function; and an eighth step of displaying the contact patch, and attaching an indication corresponding to the sound intensity of one of the leading-in side and the trailing-in side to one side of the contact patch in the tire circumferential direction, and an indication corresponding to the sound intensity of the other side of the contact patch in the tire circumferential direction.

[0008] [2] The method for displaying sound source exploration results described in [1] above, wherein in the eighth step, a display is attached to the model sound source point according to the sound intensity of either the leading side or the trailing side, and a display is attached to a point-symmetric position of the model sound source point with the center of the contact surface as the center of point symmetry according to the sound intensity of the other side.

[0009] [3] A method for displaying sound source exploration results according to the above-mentioned [1] or [2], in which the sound intensity on the leading side is calculated from the intensity at half-width of a peak selected from the sound intensity distribution on the leading side, and the sound intensity on the trailing side is calculated from the intensity at half-width of a peak selected from the sound intensity distribution on the trailing side.

[0010] [4] A method for displaying a sound source exploration result according to any one of [1] to [3] above, comprising the steps of: displaying a plurality of the model sound source points and the contact surface on the same image; listing the coordinates of pixels on the image corresponding to the model sound source points; performing a neighborhood point search using one pixel in the created list as a starting point; grouping a plurality of pixels identified by the neighborhood point search into one group; and removing pixel data included in one of the groups from the list; repeating these steps until all pixel data is removed from the list, thereby creating a plurality of groups, each of which is a set of pixels corresponding to a plurality of the model sound source points; determining the center of gravity coordinates of the model sound source points based on the coordinates of the pixels included in the group; and attaching an indication corresponding to the sound of the stepping-in side to the position of the determined center of gravity coordinates. Effect of the Invention

[0011] By providing the above-described features, the present invention can clearly display the sound source positions of noise generated on the leading side and trailing side due to tire rotation and the sound intensity distribution at the sound source positions. [Brief description of the drawings]

[0012] [Figure 1] A view of the acoustic test from the axial direction of the tire. [Diagram 2] The acoustic test scene viewed from the direction of arrow A in Figure 1. [Diagram 3] FIG. 1 is a diagram showing the configuration of a sound source tracking device. [Figure 4] FIG. 13 is a diagram showing actual measurement points using a microphone. [Diagram 5] 3 is a flowchart of a sound source localization method. [Figure 6] 4 is a flow chart for measuring sound pressure. [Figure 7] Flowchart of acoustic analysis. [Figure 8] Bottom view of the contact surface of a tire model used for acoustic analysis. [Figure 9]A view of the contact areas of the tire model for acoustic analysis and the drum model for acoustic analysis, viewed from the microphone side. [Figure 10] FIG. 13 shows the distribution of volume velocity at a model sound source point. [Figure 11] 10 is a flowchart of image processing executed in a modified example of the present invention. [Figure 12] FIG. 11 is a diagram showing the configuration of a sound source tracking device according to a second modified example of the present invention. [Figure 13] FIG. 1 shows a microphone array. [Figure 14] FIG. 11 is a view of an acoustic test of the second modified example of the present invention, viewed from the tire axial direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The embodiments will be described with reference to the drawings. Note that the embodiments described below are merely examples, and any appropriate modifications that do not depart from the gist of the present invention are included in the scope of the present invention.

[0014] 1. Configuration of the sound source identification device 1 to 3 show a sound source tracking device 10 that performs the method for displaying the sound source tracking results of this embodiment. The sound source tracking device 10 includes a drum D for rolling a tire T, a drum control device 12 to which the drum D is connected, two microphones 17 and 18 for measuring the sound pressure of the sound from the tire T, an acoustic measurement device 13 to which the microphones 17 and 18 are connected, a movement control device 19 for holding and moving the mobile microphone 17, which is one of the microphones 17 and 18, a computer 14 connected to the acoustic measurement device 13, an input device 15 connected to the computer 14, an output device 16 connected to the computer 14, and a reference signal device 11 connected to the acoustic measurement device 13.

[0015] At least the drum D and the microphones 17 and 18 of the sound source tracking device 10 are placed in an environment suitable for measuring sound, such as an anechoic chamber or a semi-anechoic chamber. In this environment, an acoustic test is performed in which the microphones 17 and 18 measure the noise generated when the drum D and the tire T are rotated.

[0016] As shown in Figures 1 and 2, the drum D is cylindrical, and the tire T comes into contact with its outer circumferential surface D1. Although not shown, a load application device for pressing the tire T against the outer circumferential surface D1 of the drum D with a predetermined force is provided on the rotation axis S of the tire T. The outer circumferential surface D1 of the drum D is smooth, and even if the outer circumferential surface D1 has many minute irregularities, it is preferable that the height difference between a convex portion and an adjacent concave portion is 1 mm or less. An example of such an outer circumferential surface D1 is a road surface with anti-slip tape attached to the drum surface.

[0017] The start and end of rotation of the drum D, and changes in the rotation speed are performed by a drum control device 12. The drum control device 12 is connected to a computer 14, and controls the rotation of the drum D based on instructions from the computer 14. A plurality of grooves 22 are formed in the tread of the tire T. When the drum D rotates (rotates clockwise as indicated by the arrow Rd in FIG. 1) with the tire T in contact with (on the ground) the drum D, the tire T rolls in the opposite direction to the rotation direction of the drum D (rolls counterclockwise as indicated by the arrow Rt in FIG. 1), and noise is generated from the contact portion G of the tire T.

[0018] One movable microphone 17 and one reference microphone 18 whose position is fixed are provided as devices for measuring the sound pressure of noise generated from the ground contact part G of the tire T. Measurement data from these microphones 17, 18 are collected by the acoustic measurement device 13 and sent to the computer 14.

[0019] Any microphone with a small measuring part at the tip can be used as the mobile microphone 17. For example, the mobile microphone 17 can be a probe microphone with a measuring part at the tip having a diameter of, for example, 0.8 mm to 1.2 mm, a 1 / 2, 1 / 4 or 1 / 8 inch microphone (i.e., a microphone with a measuring part at the tip having a diameter of 1 / 2, 1 / 4 or 1 / 8 inch), a MEMS (Micro-Electrical-Mechanical Systems) microphone, or the like.

[0020] The mobile microphone 17 is positioned so that the measurement portion at its tip approaches the ground contact portion G of the tire T against the drum D. The position of the measurement portion at the tip of the mobile microphone 17 is preferably a position 25 mm to 100 mm away from the ground contact portion G of the tire T in the tangential direction of the tire T at the ground contact portion G (the left-right direction in FIG. 1).

[0021] In this embodiment, the mobile microphone 17 is disposed on one side in the tangential direction of the tire T (the right side in FIG. 1) at the ground contact portion G of the tire T. When the tire T rotates counterclockwise as indicated by the arrow Rt in FIG. 1, the mobile microphone 17 measures the sound pressure of noise generated from the ground contact portion G of the tire T on the leading side of the tire T, and when the tire T rotates clockwise, the mobile microphone 17 measures the sound pressure of noise generated from the ground contact portion G of the tire T on the trailing side of the tire T.

[0022] The mobile microphone 17 is held by a holder (not shown) of the mobile control device 19, and is moved under the control of the mobile control device 19. The mobile control device 19 is, for example, a robot. The mobile control device 19 is connected to the computer 14, and controls the movement of the mobile microphone 17 based on instructions from the computer 14.

[0023] The measurement part at the tip of the mobile microphone 17 moves on a plane having a predetermined area. This plane is the measurement surface 20 of the sound pressure by the mobile microphone 17 (see FIG. 2). The measurement surface 20 is, for example, a plane perpendicular to the traveling direction of the noise generated from the ground contact portion G of the tire T, and is a plane perpendicular to the fore-and-aft direction of the tire T when the mobile microphone 17 is disposed in front of or behind the tire T.

[0024] FIG 4 shows an enlarged view of the measurement surface 20 measured by the mobile microphone 17. In FIG 4, the movable path of the mobile microphone 17 is shown by a dashed straight line, and the stop positions are shown by solid circles. The movable path describes a lattice (preferably a lattice that forms a square as shown in FIG 4), and the stop positions are periodically arranged up, down, left, and right. There are multiple stop positions in both the up and down directions and the left and right directions. In this embodiment, the multiple stop positions are arranged symmetrically with respect to the equatorial plane CL of the tire T.

[0025] The moving microphone 17 stops at all the stop positions shown in Fig. 4, but the order of movement is not limited thereto. As an example, as shown by the arrows in Fig. 4, the moving microphone 17 moves to the right along the movement path of the top row, moves to the left along the movement path of the second row from the top, moves to the right along the movement path of the third row from the top, and moves to the left along the movement path of the fourth row from the top, and stops at all the stop positions during these movements.

[0026] The mobile microphone 17 measures the sound pressure while stopped at each stop position. In other words, the stop positions indicated by solid circles in Fig. 4 are also the measurement points where the sound pressure is measured by the mobile microphone 17. The rectangular area surrounded by the outermost measurement points and the movable path in Fig. 4 is defined as the measurement surface 20.

[0027] The distance L between adjacent measurement points (i.e., the stop positions of the mobile microphone 17) in the vertical and horizontal directions is preferably 1 mm to 10 mm, and more preferably 4 mm to 5 mm. The movement path and measurement points of the mobile microphone 17 as described above are set in advance in the sound source tracking device 10.

[0028] The position where the reference microphone 18 is fixed is not limited, but may be, for example, the center position in the vertical direction of the measurement surface 20. The position of the reference microphone 18 in the horizontal direction is not limited, but may be, for example, within the range of the measurement surface 20, or within a range of a distance L outward from either the left or right end of the measurement surface 20 as shown in FIG.

[0029] Various microphones can be used as the reference microphone 18, for example a 1 / 2, 1 / 4 or 1 / 8 inch microphone.

[0030] The reference signal device 11 is, for example, a rotary encoder provided on a rotation shaft S of a tire T as shown in Fig. 2. When the tire T and its rotation shaft S rotate, a pulse signal corresponding to the rotation angle of the rotation shaft S is generated from this rotary encoder and sent to the computer 14. For example, a pulse signal is generated once every time the tire T and its rotation shaft S rotates one revolution, i.e., 360°.

[0031] This pulse signal is used as a reference signal for starting and ending measurement of sound pressure by the mobile microphone 17. For this purpose, the relationship between the start of measurement by the mobile microphone 17 and the pulse signal, and the relationship between the end of measurement by the mobile microphone 17 and the pulse signal are set in advance. For example, a pulse signal a predetermined number of times (e.g., the first) after the mobile microphone 17 moves to a new actual measurement point is set as a reference signal for starting measurement, and another pulse signal a predetermined number of times (e.g., the second or third) after the mobile microphone 17 moves to a new actual measurement point is set as a reference signal for ending measurement.

[0032] Because such a relationship is set, the mobile microphone 17 performs measurements at each actual measurement point from when a reference signal (pulse signal) for starting measurement is generated until a reference signal (pulse signal) for ending measurement is generated. Therefore, sound pressure can be measured for the same number of rotations of the tire T at all actual measurement points, and the measurement conditions by the mobile microphone 17 at each actual measurement point can be matched.

[0033] The acoustic measurement device 13 collects measurement data by the mobile microphone 17 and measurement data by the reference microphone 18, and sends the data to the computer 14. In the acoustic measurement device 13, the measurement data by the mobile microphone 17 at each actual measurement point is linked to the measurement data measured by the reference microphone 18 simultaneously with the measurement at each actual measurement point by the mobile microphone 17. The linked data is then sent to the computer 14.

[0034] The computer 14 has a processing unit and a memory device, and functions as a device having a sound pressure data acquisition unit 31, a device control unit 32, a volume velocity distribution creation unit 33, an output data generation unit 34, and an acoustic analysis unit 40 by the processing unit reading and executing a program stored in the memory device.

[0035] The device control unit 32 controls the movement control device 19 and the drum control device 12 .

[0036] The sound pressure data acquisition unit 31 acquires, from the acoustic measurement device 13, measurement data at each actual measurement point by the mobile microphone 17 and measurement data by the reference microphone 18 linked thereto.

[0037] The acoustic analysis unit 40 performs acoustic analysis using a model to reproduce the above-mentioned acoustic test in which noise is measured by the microphones 17, 18 while rotating the drum D and tire T. The acoustic analysis unit 40 analyzes sound transmission from a model sound source point set in the model to a model measurement point set in the model by a numerical analysis method using a model divided into elements and having nodes, specifically, finite element analysis or boundary element analysis.

[0038] As shown in FIG. 3, the acoustic analysis section 40 includes a ground contact analysis section 41, an acoustic analysis model acquisition section 42, a sound source setting section 43, a measurement point setting section 44, and a frequency response function calculation section 45.

[0039] The ground contact analysis unit 41 uses the above-mentioned finite element models of the tire T and the drum D to obtain the shape of the ground contact surface and the deformed shape of the tire T when the tire T is pressed against the drum D.

[0040] The acoustic analysis model acquisition unit 42 acquires a model for acoustic analysis (for example, a finite element model when performing finite element analysis) in which the tire T, the drum D, and the acoustic space around the tire T are modeled with a finite number of elements.

[0041] The sound source setting unit 43 sets a plurality of model sound source points for acoustic analysis at positions corresponding to the vicinity of the ground contact portion G of the tire T described above.

[0042] The measurement point setting unit 44 sets a plurality of model measurement points for the acoustic analysis at positions corresponding to the actual measurement points of the moving microphone 17 in the above-mentioned acoustic test.

[0043] The frequency response function calculation unit 45 uses the model acquired by the acoustic analysis model acquisition unit 42 to analyze the transmission of sound from the model sound source point set by the sound source setting unit 43 to the model measurement point set by the measurement point setting unit 44, and calculates a frequency response function.

[0044] The volume velocity distribution creation unit 33 creates a distribution of sound generated at the model sound source point when a test identical to the acoustic test is performed on the model, based on the measurement data on the measurement surface 20 acquired by the sound pressure data acquisition unit 31 and the frequency response function calculated by the frequency response function calculation unit 45 of the acoustic analysis unit 40. In this embodiment, the volume velocity distribution creation unit 33 creates a distribution of volume velocity as a distribution for sound.

[0045] The output data generation unit 34 generates display data to be displayed on the output device 16 based on the shape of the contact surface of the tire T on the model obtained by the contact analysis unit 41, the position of the model sound source point set by the sound source setting unit 43, and the sound distribution at the model sound source point created by the volume velocity distribution creation unit 33.

[0046] The input device 15 is a keyboard or the like that allows a person to input data to the computer 14. The output device 16 is a display or the like that outputs the results of calculations in the computer 14, such as display data generated by the output data generating unit 34.

[0047] 2. Sound source detection method and display method of sound source detection results The flow of the sound source identification method of this embodiment is shown in Fig. 5. First, an acoustic test is performed in which a tire T is rolled to measure noise (S1 in Fig. 5).

[0048] In the acoustic test, first, the tire T is placed so that it touches the drum D as shown in Fig. 1. Next, the drum D starts to rotate in a predetermined direction, and the tire T that is in contact with the drum D starts to rotate in the opposite direction to the drum D. When the tire T starts to rotate, noise begins to be generated. Also, a pulse signal is generated as a reference signal according to the rotation angle of the tire T and the rotating shaft S.

[0049] Next, the sound pressure is measured by the microphones 17 and 18. The measurement of the sound pressure will be described with reference to FIG.

[0050] First, the mobile microphone 17 moves to the first actual measurement point (S1-1 in FIG. 6) and waits at that actual measurement point (S1-2 in FIG. 6). Then, when a reference signal to start measurement is issued while waiting (YES in S1-3 in FIG. 6), the mobile microphone 17 starts measuring the sound pressure (S1-4 in FIG. 6). Next, when a reference signal to end measurement is issued while measuring the sound pressure (YES in S1-5 in FIG. 6), the mobile microphone 17 ends measuring the sound pressure (S1-6 in FIG. 6). As a result, the mobile microphone 17 performs measurement from when the reference signal to start measurement is issued until when the reference signal to end measurement is issued.

[0051] After that, if measurements at all the actual measurement points have not been completed (NO in S1-7 in FIG. 6), the moving microphone 17 moves to the next actual measurement point (S1-1 in FIG. 6), and steps S1-2 to S1-6 are performed again. If measurements at all the actual measurement points have been completed (YES in S1-7 in FIG. 6), the sound pressure measurement ends.

[0052] On the other hand, it is sufficient that the measurement of sound pressure by the reference microphone 18 is performed at least in synchronization with the measurement of sound pressure by the mobile microphone 17. Therefore, the reference microphone 18 may continue to measure sound pressure from the start of measurement at the first actual measurement point by the mobile microphone 17 to the end of measurement at the last actual measurement point. Also, the reference microphone 18 may start and end measurement every time the mobile microphone 17 starts and ends measurement based on the reference signal.

[0053] In this way, measurements by the mobile microphone 17 and the reference microphone 18 are performed in synchronization, so that the measurement data at each actual measurement point by the mobile microphone 17 is linked to the corresponding measurement data by the reference microphone 18.

[0054] In the acoustic test described above, a first measurement is performed in which tire T is rotated counterclockwise as shown by arrow Rt in FIG. 1 and the sound pressure of noise generated from the contact portion G of tire T is measured with movable microphone 17 from the leading side of tire T, and a second measurement is performed in which tire T is rotated clockwise and the sound pressure of noise generated from the contact portion G of tire T is measured with movable microphone 17 from the trailing side of tire T.

[0055] After the first and second measurements are completed in this manner, acoustic analysis is then performed (S2 in FIG. 5). The acoustic analysis will be described with reference to FIG.

[0056] First, the ground contact analysis unit 41 acquires a finite element model of the tire T (hereinafter referred to as the "tire FE model") and a finite element model of the drum D (hereinafter referred to as the "drum FE model") (S2-1 in FIG. 7). These finite element models are created from a three-dimensional CAD model of the tire T used in the acoustic test and a three-dimensional CAD model of the drum D used in the acoustic test. These finite element models may be stored in advance in a storage device of the computer 14, may be acquired by input from the input device 15, or may be acquired via a network (not shown). In the finite element model, the physical property values ​​of the actual tire T and drum D and conditions required for the finite element analysis are set.

[0057] Next, the ground contact analysis unit 41 performs a ground contact analysis (S2-2 in FIG. 7). Specifically, the ground contact analysis unit 41 brings the tire FE model into contact with the drum FE model, applies the same load as in the acoustic test to the tire FE model, and performs calculations to deform the tire FE model. Then, the shape of the tire FE model after deformation, as well as the shape and contact area of ​​the contact surface between the tire FE model and the drum FE model are acquired.

[0058] Next, the acoustic analysis model acquisition unit 42 acquires a model for acoustic analysis of the tire T (hereinafter referred to as the "tire model for acoustic analysis") and a model for acoustic analysis of the drum D (hereinafter referred to as the "drum model for acoustic analysis") (S2-3 in FIG. 7).

[0059] The tire model for acoustic analysis is a three-dimensional model of the tire T used in the acoustic test, and is a model of the same deformed shape as the tire FE model after deformation obtained by the contact analysis. The tire model for acoustic analysis has a plurality of main grooves 22 extending in the tire circumferential direction, and lands 23 defined by the main grooves 22. Note that the tire model for acoustic analysis may have not only the main grooves 22, but also slits 26 and sipes 27 extending in the tire axial direction (see Figs. 8 and 9).

[0060] The drum model for acoustic analysis is a 3D model of the drum D used in the acoustic test. The drum model for acoustic analysis is a type of road surface model that models the road surface with which the tire T comes into contact.

[0061] The tire model for acoustic analysis is placed in a position pressed against the drum model for acoustic analysis. The shape and area of ​​the contact surface between the tire model for acoustic analysis and the drum model for acoustic analysis are the same as those obtained in the contact analysis.

[0062] Moreover, the acoustic analysis model acquisition unit 42 acquires an acoustic space model that models an acoustic space around the tire in which neither an acoustic analysis tire model nor an acoustic analysis drum model exists (S2-4 in FIG. 7).

[0063] The tire model for acoustic analysis, the drum model for acoustic analysis, and the acoustic space model are models divided into elements and have nodes, and are models that allow for numerical analysis such as finite element analysis and boundary element analysis. These models are created from a three-dimensional CAD model. These models may be stored in advance in a storage device of the computer 14, or may be acquired by input from the input device 15, or may be acquired via a network (not shown) or the like.

[0064] In addition, the mesh sizes of the tire model for acoustic analysis, the drum model for acoustic analysis, and the acoustic space model are preferably sizes that can reproduce the deformed shape of the tire T and the contact shape between the tire T and the drum D, and are smaller than the upper limit of the frequency to be measured, for example, smaller than 1 / 10 of the wavelength of the upper limit of the frequency to be measured.

[0065] Necessary boundary conditions are set for the acoustic analysis tire model and the acoustic analysis drum model. For example, the acoustic analysis tire model and the acoustic analysis drum model are set as perfect reflectors that do not absorb sound and reflect 100%. In addition, the acoustic analysis tire model and the acoustic analysis drum model are set as rigid body models that do not deform.

[0066] When the acoustic analysis is performed by finite element analysis, the tire FE model and drum FE model used in the ground contact analysis may be used as they are as the tire model for acoustic analysis and the drum model for acoustic analysis.

[0067] Next, the sound source setting unit 43 sets a plurality of model sound source points in the vicinity of the contact surface between the tire model for acoustic analysis and the drum model for acoustic analysis (S2-5 in FIG. 7).

[0068] Specifically, in the acoustic analysis, a plurality of model sound source points are set on one side of the contact patch in the tire circumferential direction by the sound source setting unit 43. In this embodiment, the setting of a plurality of model sound source points by the sound source setting unit 43 is performed via an operation from the input device 15.

[0069] 8 and 9, model sound source points set through operations on the input device 15 are indicated by black dots. Although not shown, the tire model for acoustic analysis t, the drum model for acoustic analysis d, and the acoustic space in Figs. 8 and 9 are divided into elements and nodes are set.

[0070] The model sound source point is the volume velocity (m 3 / sec) of the input point. The frequency of the fluctuations of the volume velocity of the first model source point can be varied.

[0071] One or more model sound source points are set for each land 23, and one or more model sound source points are set for each main groove 22. In addition, model sound source points are set for all of the lands 23 and all of the main grooves 22.

[0072] The model sound source point set for the land 23 is set to a node in the vicinity of the ground contact end (the tire circumferential end of the ground contact surface) of the land 23 among the nodes of the acoustic space model, for example, set to the node closest to the ground contact end of the land 23. It is preferable that all of the model sound source points set for the multiple lands 23 have the same distance from the tire circumferential end of the ground contact surface in the tire circumferential direction CD. It is also preferable that all of the multiple model sound source points set for the multiple lands 23 have the same height (distance in the direction perpendicular to the tread surface) from the outer circumferential surface (tread surface) of the acoustic analysis tire model t.

[0073] 8 and 9, the model sound source point set for the main groove 22 is set at the open end of the main groove 22 at the position of the ground contact end of the tire model t for acoustic analysis among the nodes of the acoustic space model. Here, the open end of the main groove 22 refers to the open end of one hollow tube 24 (see FIG. 9) formed by the outer circumferential surface of the drum model d for acoustic analysis and the main groove 22 of the tire model t for acoustic analysis. It is preferable that the model sound source point is set at the center of the open end.

[0074] Next, the measurement point setting unit 44 sets model measurement points for sound pressure in acoustic analysis (S2-6 in FIG. 7). The model measurement points are set at the same positions as all measurement positions by the movable microphone 17 during acoustic testing. Although not shown, the measurement points are set at the top of FIG. 8. Setting of the model measurement points in the model by the measurement point setting unit 44 is performed via operation from the input device 15.

[0075] Next, the frequency response function calculation unit 45 executes an acoustic analysis using a known method (S2-7 in FIG. 7).

[0076] In the acoustic analysis, first, a frequency response function of sound from a plurality of model sound source points set by the sound source setting unit 43 to a model measurement point is obtained.

[0077] Specifically, the volume velocity (m 3 / sec) is input, and sound pressure (Pa) is calculated at a plurality of model measurement points set by the measurement point setting unit 44. The frequency of the sound pressure fluctuation at the model measurement points obtained by calculation is the same as the frequency of the volume velocity fluctuation at the model sound source point.

[0078] Let q1, q2, qn(m 3 / sec) and the sound pressures at m model measurement points are p1, p2, pm (Pa), the following relationship can be obtained by acoustic analysis:

[0079]

number

[0080]

number

[0081] The frequency response function H is calculated for each frequency of the volume velocity fluctuation at the model sound source point. Therefore, the frequency response function H is calculated for each predetermined frequency from the lower limit to the upper limit of the frequency to be evaluated. Then, when the frequency response function H is calculated, the acoustic analysis ends.

[0082] Next, the volume velocity distribution creation unit 33 calculates a first distribution, which is the distribution of sound at the model sound source point, and a first intensity, which is the intensity of the sound, based on the measurement data on the measurement surface 20 acquired by the sound pressure data acquisition unit 31 during the first measurement and the frequency response function H calculated by the frequency response function calculation unit 45 of the acoustic analysis unit 40 (S3 in FIG. 5).

[0083] Specifically, in the first measurement, the sound pressure measurement at each actual measurement point is performed over a predetermined time, so the measurement data acquired at each actual measurement point is time-series data. This time-series data is Fourier transformed to acquire data on sound pressures P1, P2, ... Pm (Pa) for each frequency. Next, the sound pressures P1, P2, ... Pm (Pa) and the inverse function H of the frequency response function H calculated by the frequency response function calculation unit 45 are calculated for each frequency. -1 Based on this, the volume velocities Q1, Q2, ... Qn (m 3 / sec) is calculated.

[0084]

number

[0085]

number

[0086] The calculation using Equation 3 may be performed for each frequency at a predetermined interval between the lower limit and the upper limit of the frequency to be evaluated. Also, the calculation using Equation 3 may be performed only for a specific frequency of interest.

[0087] In the first measurement, the sound generated when the tire T is rolling is measured from the leading side. Therefore, based on the measurement data obtained in the first measurement, the volume velocities Q1, Q2, ... Qn at each model sound source point calculated using Equation 3 can be regarded as the volume velocities of sound on the leading side generated at positions equivalent to the model sound source points in the tire T during the acoustic test.

[0088] In this way, the volume velocity of the sound on the stepping side generated at the positions of multiple model sound source points is obtained for each frequency, and a distribution (first distribution) of the volume velocity (intensity) of the generated sound of each wavelength is obtained for each model sound source point.

[0089] Then, the volume velocity distribution creation unit 33 selects a predetermined peak from the obtained first distribution, and calculates the total value of the volume velocities of the wavelengths included in the half-width of the selected peak as the first intensity. The volume velocity distribution creation unit 33 calculates the first intensity for each model sound source point. Note that the peak selected by the volume velocity distribution creation unit 33 when calculating the first intensity may be, for example, a peak with the largest peak value in the first distribution, or a peak present in the frequency band to be evaluated.

[0090] From the above, the volume velocity distribution creating unit 33 obtains a first distribution which is a distribution of the sound on the leading side at each model sound source point, and a first intensity which is the intensity of the sound on the leading side at each model sound source point.

[0091] In addition, the volume velocity distribution creation unit 33 also calculates a second distribution, which is the distribution of sound at the model sound source point, and a second intensity, which is the intensity of sound, for the measurement data acquired in the second measurement, based on the frequency response function H calculated by the frequency response function calculation unit 45 of the acoustic analysis unit 40, using the same procedure as for the first measurement described above (S4 in FIG. 5).

[0092] That is, the measurement data of the second measurement is Fourier transformed to obtain data of sound pressures P1, P2, ... Pm (Pa) for each frequency. Next, the sound pressures P1, P2, ... Pm (Pa) and the inverse function H of the frequency response function H are calculated for each frequency. -1 Based on this, the volume velocities Q1, Q2, ... Qn (m3 / sec) is calculated.

[0093] In the second measurement, the sound generated when the tire T is rolling is measured from the trailing edge. Therefore, based on the measurement data obtained in the second measurement, the volume velocities Q1, Q2, ... Qn at each model sound source point calculated using Equation 3 can be regarded as the volume velocities of the sound on the trailing edge generated at positions equivalent to the model sound source points in the tire T during the acoustic test.

[0094] In this way, the volume velocity on the kick-out side at the positions of multiple model sound source points is obtained for each frequency, and a distribution (second distribution) of the volume velocity (intensity) of the generated sound of each wavelength is obtained for each model sound source point.

[0095] Then, the volume velocity distribution creation unit 33 selects a predetermined peak from the obtained second distribution, and calculates the sum of the volume velocities of the wavelengths included in the half-width of the selected peak as the second intensity. The volume velocity distribution creation unit 33 calculates the second intensity for each model sound source point. Note that the peak selected by the volume velocity distribution creation unit 33 when calculating the second intensity may be, for example, a peak with the largest peak value in the second distribution, or a peak present in the frequency band to be evaluated.

[0096] The output data generation unit 34 generates display data for displaying on the output device 16 a display such as that shown in FIG. 10 based on the shape of the contact surface of the tire T determined by the contact analysis unit 41, the position of the model sound source point set by the sound source setting unit 43, and the first intensity and second intensity calculated by the volume velocity distribution creation unit 33 (S5 in FIG. 5).

[0097] Specifically, as shown in FIG. 10, the output data generation unit 34 generates data that displays the contact surface of the tire T determined by the contact analysis unit 41 and indicates the position of the model sound source point according to either the first intensity or the second intensity (e.g., the first intensity) calculated by the volume velocity distribution creation unit 33.

[0098] In addition, the output data generation unit 34 generates data in which an indication is added according to the other of the first intensity and the second intensity (e.g., the second intensity) calculated by the volume velocity distribution creation unit 33 at a point-symmetric position of the model sound source point with the center (center of gravity) C of the contact surface as the point symmetry center.

[0099] In Fig. 10, the black circles indicate the first intensity and show the sound intensity on the leading side at each model sound source point. The white circles indicate the second intensity and show the sound intensity on the trailing side at each model sound source point. For both black and white circles, the larger the circle, the greater the intensity (volume velocity), meaning that a louder noise is being generated.

[0100] In this embodiment, the intensity is represented by the size of the circle placed at the position of the model sound source point, but the intensity at each position may be displayed by adding an indication corresponding to the sound intensity at the position of each model sound source point using various methods, such as the color of the circle (color contour or grayscale).

[0101] 3. Effects of the embodiment In this embodiment, the contact surface of the tire model is displayed, and the display according to the intensity of the noise on the leading side and the noise on the trailing side generated at the position of each model sound source point is displayed on both sides of the contact surface of the tire model in the tire circumferential direction. Therefore, the sound source positions of the noise generated on the leading side and the trailing side and the sound intensity at the sound source positions can be displayed in an easy-to-understand manner, and the design of the tread pattern can be easily changed to reduce the noise generated from the tire.

[0102] In this embodiment, the intensity of noise from either the leading-in side or the trailing-off side is displayed at the position of the model sound source point, and the intensity of the other noise is displayed at a position symmetrical to the model sound source point with the center of the contact patch as the center of point symmetry, so there is no need to set model sound source points on both sides of the contact patch in the circumferential direction of the tire.

[0103] In this embodiment, the first intensity on the leading side and the second intensity on the trailing side displayed at the model sound source point are the intensities at the half-width of a predetermined peak selected from the sound intensity distribution at each model sound source point, so that the noise intensity can be displayed with high accuracy.

[0104] 4. Example of changes Modifications of the above-described embodiment will be described. Any one of the multiple modification examples described below may be applied to the above-described embodiment, or any two or more of the modification examples described below may be applied in combination. In addition to the following modification examples, various modifications are possible.

[0105] (1) Change Example 1 In the above embodiment, when the output data generating unit 34 generates a display as shown in Fig. 10, the positions of the model sound source points set by the sound source setting unit 43 can be automatically determined from the ground surface image. In this modification, the model sound source points can be specified, for example, by a procedure as shown in Fig. 11.

[0106] That is, first, the model sound source point and the ground surface set during acoustic analysis are displayed on the same image (hereinafter, this image is referred to as an analysis image) (S101 in FIG. 11). At that time, it is preferable to display the ground surface in white, the sound source point identified by acoustic analysis in red, and the parts other than the ground surface and the sound source point (for example, the background part) in black, and adjust the display color of each part so that the contrast between the ground surface, the sound source point identified by acoustic analysis, and the other parts is increased.

[0107] Then, the coordinates of pixels corresponding to the sound source points identified by acoustic analysis from the analysis image are listed (S102 in FIG. 11). For example, if the sound source points identified by acoustic analysis are displayed in red, the red coordinates are extracted from the analysis image, and the extracted coordinates are rearranged in the order of one coordinate (for example, X coordinate) and listed.

[0108] Next, a pixel that is to be the starting point of the neighboring point search is specified. In this modification, the first pixel in the created list, that is, the pixel with the smallest X coordinate among the red pixels, is specified as the starting point of the neighboring point search (S103 in FIG. 11).

[0109] Next, a neighborhood search is performed with the pixel specified in step S103 as the starting point (S104 in FIG. 11). The neighborhood search is a method of repeatedly specifying a pixel that is within a predetermined range of the previously specified pixel and is closest to the previously specified pixel as the next pixel, thereby extracting a set of the specified multiple pixels. Note that "closest" means that the distance is the shortest.

[0110] Specifically, first, among the pixels in the list other than the starting point, a pixel that is within a predetermined range from the starting point and is closest to the starting point is searched for, and the found pixel is specified as the second pixel. Next, among the pixels in the list that are not yet specified, a pixel that is within a predetermined range from the second pixel and is closest to the second pixel is searched for, and the found pixel is specified as the third pixel. In this manner, the pixel closest to the previously specified pixel (a pixel that has not been specified up to that point and is within a predetermined range from the previously specified pixel) is repeatedly specified as the next pixel. Note that, if there are multiple "pixels closest to the previously specified pixel," only one of them may be specified as the next pixel, or all of them may be specified as the next pixel at the same time.

[0111] In this way, only pixels within the predetermined range are specified as the next pixel, and only pixels that form a single group in the analysis image are extracted. Then, when the next pixel closest to the previously specified pixel is no longer within the predetermined range and the next pixel can no longer be specified, the neighboring point search ends. Here, the "predetermined range" in this modified example refers to the range adjacent to the previously specified pixel up, down, left, right, and diagonally.

[0112] Next, all pixels identified by the neighboring point search in step S104 are grouped together (S105 in FIG. 11). The group created at this time is called group 1. The first group is made up of pixel data constituting the sound source point with the smallest X coordinate in the analysis image.

[0113] Next, data of all pixels included in the first group created in step S105 is removed from the list (first list) created in step S102 (S106 in FIG. 11). The list after the removal is designated as a second list.

[0114] Next, it is confirmed whether there is any pixel data left in the list (second list), that is, whether there is any data in the list (S107 in FIG. 11). If data of pixels that were not included in the first group remain in the second list ("Yes" in S107 in FIG. 11), the process returns to step S103 again, and the start point of the next neighboring point search is identified. At this time, the pixel with the smallest X coordinate in the second list from which the first group has been removed is identified as the start point of the next neighboring point search. Then, the neighboring point search is performed in step S104, a second group, which is the second group, is created in step S105, and data of all pixels included in the second group is removed from the second list in step S106.

[0115] In this manner, the following steps are repeated until there is no more data in the list: identifying the pixel with the smallest X coordinate in the nth list (the list obtained by removing all pixels from the first list to the (n-1)th group) as the starting point (S103 in FIG. 11); executing a neighborhood search from the starting point (S104 in FIG. 11); classifying the pixels obtained by the neighborhood search into the nth group (S105 in FIG. 11); and removing data of all pixels included in the nth group from the nth list (S106 in FIG. 11). Then, when there is no more pixel data in the list in step S107 ("No" in S107 in FIG. 11), the image processing ends.

[0116] By such image processing, a plurality of groups, which are collections of sound source points appearing in the analysis image, are created.

[0117] Then, for each group created by the above image processing, the barycentric coordinates of all pixels included in the group are obtained. The barycentric coordinates are calculated from the coordinates of all pixels included in the group. The sound source setting unit 43 sets the obtained barycentric coordinates of each group as a model sound source point (S108 in FIG. 11).

[0118] Then, similarly to the embodiment described above, the output data generation unit 34 generates display data for displaying on the output device 16 the display as illustrated in FIG. 10 based on the shape of the contact surface of the tire T determined by the contact analysis unit 41, the position of the model sound source point set by the sound source setting unit 43, and the first intensity and second intensity calculated by the volume velocity distribution creation unit 33.

[0119] In this modification, the positions of a plurality of model sound source points can be identified on the ground surface image, and the corresponding sound source strength results can be automatically displayed, making it possible to easily generate display data.

[0120] (2) Change Example 2 In this modification, instead of the mobile microphone 17, a microphone array 111 is used, in which a microphone is fixed at each of a number of measurement positions.

[0121] 12 shows a sound source tracking device 110 used to implement the sound source tracking method of this modified example. The sound source tracking device 110 of this modified example differs from the sound source tracking device 10 of the above embodiment in that, instead of the mobile microphone 17 and the reference microphone 18, multiple measurement microphones 112 and one reference microphone 114 are provided as devices for measuring sound pressure. The multiple measurement microphones 112 and the reference microphone 114 are connected to the sound pressure data acquisition unit 31.

[0122] As shown in FIG. 13, microphone array 111 is composed of a plurality of measurement microphones 112 (indicated by solid single circles in FIG. 13) and one reference microphone 114 (indicated by solid double circles in FIG. 13). In microphone array 111, microphones 112, 114 are arranged in a lattice pattern (preferably a lattice pattern forming a square as shown in FIG. 13) and are periodically lined up vertically and horizontally. The positions of each microphone 112, 114 are measurement positions where sound pressure is measured. It is preferable that there are two or more measurement positions in the vertical direction and four or more measurement positions in the horizontal direction. The distance L between adjacent measurement positions in the vertical and horizontal directions is, for example, 25 mm to 35 mm.

[0123] As the measurement microphone 112 and the reference microphone 114, for example, a probe microphone with a measuring tip diameter of 0.8 mm to 1.2 mm, a 1 / 2, 1 / 4 or 1 / 8 inch microphone, or a MEMS (Micro-Electrical-Mechanical Systems) microphone can be used.

[0124] The surface surrounded by the outermost measurement microphones 112 of the microphone array 111 is a sound pressure measurement surface 130. This measurement surface 130 is disposed perpendicular to the traveling direction of noise generated from the ground contact portion G of the tire T, for example.

[0125] 14, microphone array 111 is disposed close to a contact portion G of tire T with drum D. The measurement position of sound pressure by microphone array 111 (i.e., the position of the measurement portion at the tip of each of microphones 112, 114 constituting microphone array 111) is preferably a position 25 mm to 200 mm away from contact portion G of tire T in the tangential direction of tire T at contact portion G (left and right direction in FIG. 14).

[0126] The microphone array 111 is disposed at a location in front of or behind the tire T. A more preferable location for disposing the microphone array 111 is a location under the tire T at the front or rear of the tire T as shown in Fig. 13 (in other words, a location at the front or rear of the tire T and between the tread surface T1 of the tire T and the outer circumferential surface D1 of the drum D). The microphone array 111 is preferably disposed so that its measurement surface 130 is perpendicular to the front-to-rear direction of the tire T.

[0127] In such a microphone array 111, all of the measurement microphones 112 and the reference microphone 114 measure the sound pressure simultaneously. Therefore, the measurement of the sound pressure in the acoustic test can be completed in a short time. The measured sound pressure data is input to the sound pressure data acquisition unit 31.

[0128] When the sound pressure data measured by the microphone array 111 is input into the sound pressure data acquisition unit 31, as in the above embodiment, the volume velocity distribution creation unit 33 creates a distribution of sound generated at the model sound source point when a test identical to the acoustic test is performed on the model, based on the measurement data at the measurement surface 130 acquired by the sound pressure data acquisition unit 31 and the frequency response function calculated by the frequency response function calculation unit 45 of the acoustic analysis unit 40.

[0129] (3) Change Example 3 In the above embodiment, the movable microphone 17 is provided only on one side of the tire T in the tangential direction at the contact portion G of the tire T, but the movable microphone 17 or the microphone array 111 as in Modification Example 2 may be provided on both sides of the tire T in the tangential direction at the contact portion G of the tire T. By providing the movable microphones 17 on both sides of the tangential direction of the tire T, it is possible to measure the sound pressure of noise generated from the contact portion G of the tire T from the leading side and trailing side of the tire T by rotating the tire T in one direction, either clockwise or counterclockwise. [Explanation of symbols]

[0130] D...drum, d...drum model for acoustic analysis, D1...outer surface, G...ground contact portion, S...rotating shaft, T...tire, t...tire model for acoustic analysis, T1...tread surface, 10...sound source exploration device, 11...reference signal device, 12...drum control device, 13...sound measurement device, 14...computer, 15...input device, 16...output device, 17...movable microphone, 18...reference microphone, 19...movable control device, 20...measurement surface, 22...main groove, 23...land portion, 24...pipe, 31...sound pressure data acquisition unit, 32...device control unit, 33...volume velocity distribution creation unit, 34...output data generation unit, 40...acoustic analysis unit, 41...ground contact analysis unit, 42...acoustic analysis model acquisition unit, 43...sound source setting unit, 44...measurement point setting unit, 45...frequency response function calculation unit

Claims

1. A first step of setting a plurality of measurement points at which sounds generated when an actual tire is rotated are measured with a microphone; A second step of acquiring a road surface model, a tire model in contact with the road surface model, and an acoustic space model around the tire; a third step of setting a plurality of model sound source points on one side in a tire circumferential direction of the contact surface of the tire model; a fourth step of setting a plurality of model measurement points at positions corresponding to the plurality of actual measurement points; A fifth step of performing an acoustic analysis using the road surface model, the tire model, and the acoustic space model to obtain a frequency response function of a sound from the model sound source point to the model measurement point; a sixth step of measuring a sound generated when an actual tire is rolled from the leading side by the microphones arranged at a plurality of the measurement points, and determining a sound intensity distribution on the leading side and a sound intensity on the leading side at the model sound source point based on the measured sound and the frequency response function; a seventh step of measuring the sound generated when an actual tire is rolled from the trailing edge by the microphones arranged at the plurality of measurement points, and determining the sound intensity distribution on the trailing edge at the model sound source point and the sound intensity on the trailing edge based on the measured sound and the frequency response function; an eighth step of displaying the ground contact surface, and attaching a display corresponding to the intensity of the sound of either the leading side or the trailing side to one side of the ground contact surface in the tire circumferential direction, and attaching a display corresponding to the intensity of the sound of the other side to the other side of the ground contact surface in the tire circumferential direction; A method for displaying sound source localization results, including:

2. In the eighth step, 2. The method for displaying sound source exploration results according to claim 1, further comprising the steps of: marking the model sound source point with a display according to the sound intensity of either the leading side or the trailing side; and marking a display with a display according to the sound intensity of the other side at a point-symmetric position of the model sound source point with the center of the contact surface as the center of point symmetry.

3. determining the intensity of the sound on the leading side from the intensity at half width of a peak selected from the intensity distribution of the sound on the leading side; 2. The method for displaying sound source exploration results according to claim 1, further comprising the step of: determining the intensity of the sound on the trailing edge side from an intensity at half width of a peak selected from the sound intensity distribution on the trailing edge side.

4. Displaying a plurality of the model sound source points and the ground plane on the same image; Listing the coordinates of pixels on the image corresponding to the model sound source points; a step of performing a neighborhood point search using one pixel in the created list as a starting point, a step of grouping a plurality of pixels identified by the neighborhood point search into one group, and a step of removing pixel data included in one of the groups from the list are repeated until all pixel data is removed from the list, thereby creating a plurality of groups, each of which is a set of pixels corresponding to a plurality of the model sound source points; determining the center of gravity coordinates of the model sound source point based on the coordinates of pixels included in the group; 2. The method for displaying sound source exploration results according to claim 1, wherein an indication according to the sound intensity of one of the leading side and the trailing side determined in the seventh step is added to the position of the determined center of gravity coordinate, and an indication according to the sound intensity of the other side is added to a point-symmetric position of the center of gravity coordinate with the center of the contact surface as a point symmetric center.

Images