JP7133458B2 - Sound source identification method - Google Patents

Description

The present invention relates to a sound source localization method.

A microphone array in which a large number of microphones are arranged vertically and horizontally is known. As described in Patent Document 1, the sound pressure of noise generated from a rotating tire is measured with such a microphone array, and acoustic holography is used to identify the source of the noise. In addition to measuring the sound pressure of noise by rotating tires on a drum as described in Patent Document 1, a vehicle equipped with tires is run on a road surface to measure the sound pressure of external sounds in the vicinity of the tires. Measurements are also taken. Conventionally, when the vehicle is driven on the road surface and the sound pressure of the external sound is measured, the extension member is fixed to the vehicle body.

Japanese Patent No. 5089253

However, since the suspension is interposed between the body and tires, the positional relationship between the body and tires changes each time the vehicle accelerates, turns, or climbs over bumps on the road surface. There is a problem that the positional relationship between the noise source and the microphone array changes. There is also the problem that the microphone array measures the sound pressure generated when the tires run over bumps on the road surface. For these reasons, the conventional method cannot accurately identify the sound source of the noise in the vicinity of the tires when the vehicle is running on the road surface.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for precisely identifying a noise source in the vicinity of a tire when a vehicle is running on a road surface.

The sound source investigation method of the embodiment is a sound source investigation method in which noise generated from tires is measured outside a running vehicle, and the sound source of the noise is specified based on the measurement data. Noise is measured by a noise measuring device attached to the rotating part, and when the tires run over bumps on the road surface, a detector attached to any part of the vehicle detects that the tires are on the road surface. The data obtained when the projection is overcome is excluded, and the data after the exclusion is used to identify the sound source.

According to the above-described embodiment, the positional relationship between the noise measuring device and the tire does not change, and the data of the sound generated when the tire runs over the bumps on the road surface is excluded, so the noise source can be determined with high accuracy. identified.

A conceptual diagram of a sound source probing device. Front view of a microphone array. FIG. 4 is a diagram of a microphone array arranged in front of or behind a tire as seen from the front-rear direction of the tire; FIG. 4 is a diagram of a microphone array arranged in front of or behind a tire as seen from the axial direction of the tire; FIG. 4 is a view of the microphone array arranged near the ground contact portion on the side of the tire as seen from the axial direction of the tire; FIG. 2 is a diagram of a microphone array arranged on the side of a tire so as to cover the entire tire, as seen from the axial direction of the tire; The figure which looked at the tire from the front-back direction. The figure when the non-rotating part is attached to the wheel. A flow chart of a sound source probing method. Image diagram of acoustic holography processing.

Embodiments will be described based on the drawings. It should be noted that the embodiment described below is merely an example, and any suitable modifications within the scope of the present invention are included in the scope of the present invention.

<Regarding the Sound Source Probing Device of the Embodiment>
FIG. 1 shows an example of a sound source probing device 10 used for carrying out the sound source probing method of this embodiment. The sound source tracking device 10 has a microphone array 12 as a noise measuring device for measuring the sound pressure of noise. The sound source probing device 10 includes an acoustic holography device 16 to which the microphone array 12 is connected, a computer 18 to which the acoustic holography device 16 is connected, and an output device 20 such as a display for outputting the calculation results of the computer 18. have. Further, the sound source tracking device 10 has a load measuring device 22 for measuring the load applied to the tires. A load measuring device 22 is connected to the computer 18 .

As shown in FIG. 2, the microphone array 12 is composed of a large number of small microphones 13 arranged vertically and horizontally. These small microphones 13 form one measuring plane. These small microphones 13 simultaneously measure the sound pressure.

The microphone array 12 is arranged at a place where the noise generated from the ground contact portion G of the tire T can be measured. For example, it is arranged in front or behind the tire T as shown in FIGS. 3 and 4, or in a lateral position of the tire T as shown in FIGS. 3 to 5, a relatively small microphone array 12 may be arranged near the ground contact portion G of the tire T, and a relatively large microphone array 12 may be arranged on the tire T as shown in FIG. You may arrange|position so that the whole may be covered.

In order to measure the noise generated from the ground contact portion G of the tire T while measuring as little background noise as possible, the lower end 11 of the microphone array 12 is preferably positioned as low as possible. However, it is preferable that the lower end 11 of the microphone array 12 is located at a certain distance from the road surface S so that the lower end 11 of the microphone array 12 does not hit the road surface S when the tire T is flexed. Therefore, the height of the lower end portion 11 of the microphone array 12 is higher than the half position H of the height L of the ground contact side portion of the tire T and lower than the boundary B between the tire T and the rim R, as shown in FIG. is preferred. The ground contact side portion of the tire T is, in other words, the portion of the tire T below the rotating shaft.

Here, the height L of the contact side portion of the tire T is the regular internal pressure (i.e., the maximum value of the "maximum air pressure" in JATMA standards, the maximum value of "TIRELOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA standards, or "INFLATION" in ETRTO standards. PRESSURE") is the height from the ground contact portion G of the tire T to the tip of the beet toe of the tire T when the tire T is mounted on a stationary vehicle. Rim R is a regular rim (that is, "standard rim" in JATMA standards, "DesignRim" in TRA standards, or "MeasuringRim" in ETRTO standards), and boundary B between tire T and rim R is 4, the boundary between the tire T and the rim R when the tire T is viewed from the side.

Also, the linear distance from the ground contact portion G of the tire T to the lower end portion 11 of the microphone array 12 is determined, for example, by the frequency to be evaluated. As an example, the distance from the ground contact portion G of the tire T to the lower end portion 11 of the microphone array 12 is set to 100 mm or more and 150 mm or less in order to accurately identify a sound source with a frequency of about 1600 Hz.

The microphone array 12 is attached to a non-rotating portion that moves up and down together with the tire T. As shown in FIG. The non-rotating portion that moves up and down together with the tire T is, for example, any portion that does not rotate and is closer to the tire T than the suspension 35 (see FIG. 3) of the vehicle.

In FIG. 3, the microphone array 12 is attached to a lower arm 30 (also referred to as a suspension arm), which is a non-rotating portion that moves up and down together with the tire T. As shown in FIG. Fixtures 24 are used for attachment. The fixture 24 is a member that extends from the lower arm 30 to the vicinity of the ground contact portion G of the tire T, and has one end fixed to the lower arm 30 and the other end fixed to the microphone array 12 .

Other non-rotating parts that move up and down together with the tire T include the knuckle 31 and the damper fork 32 . Further, as shown in FIG. 7, a rotating member 27 that rotates integrally with the wheel 33 is attached to the vehicle outer side surface of the wheel 33, and a non-rotating member 29 is provided on the vehicle outer side portion of the rotating member 27 via a bearing. The non-rotating member 29 may be a non-rotating portion that moves up and down together with the tire T. The non-rotating member 29 is fixed to any part of the vehicle so as not to rotate integrally with the rotating member 27 . The microphone array 12 is attached via the fixture 24 to the non-rotating portion that moves up and down together with the tire T illustrated above.

If the posture of the microphone array 12 becomes unstable only with the fixture 24, an auxiliary member connects the microphone array 12 and any part of the vehicle to stabilize the posture of the microphone array 12. Also good.

The acoustic holography device 16 acquires sound pressure measurement data from the microphone array 12, performs acoustic holography processing, which will be described later, and calculates the sound pressure distribution at the contact portion G of the tire T. FIG. The computer 18 also controls the connected acoustic holography device 16 . Then, the sound pressure distribution at the ground contact portion G of the tire T obtained by the acoustic holography device 16 is output to the output device 20 .

A load cell, for example, is used as the load measuring device 22 . The load measuring device 22 is attached to a place where the load applied to the tire T can be measured, for example, the axle 34 . When the tire T runs over the bump on the road surface S, a load is applied to the tire T, so the load measuring device 22 can detect that the tire T has run over the bump on the road surface S.

<Regarding the sound source probing method of the embodiment>
FIG. 8 shows a rough flow of the sound source probing method of this embodiment. First, the vehicle starts running (S1), and the tires T start rolling on the road surface S accordingly. When the tire T rolls on the road surface S, noise is generated. Next, the sound pressure of noise is measured by the microphone array 12 (S2). Next, based on the sound pressure measurement data, the sound pressure distribution at the ground contact portion G of the tire T is calculated using acoustic holography (S3). Next, the sound source is specified based on the sound pressure distribution in the contact portion G of the tire T (S4).

In steps S1 and S2 described above, the microphone array 12 is attached to a non-rotating portion that moves up and down together with the tires T even if the vehicle accelerates, turns, or climbs over bumps on the road surface S while running. Therefore, the positional relationship between the microphone array 12 and the tire T does not change. Further, when the tire T gets over the protrusion, the load measuring device 22 detects it. Sound pressure measurement by the microphone array 12 and load measurement by the load measuring device 22 are performed simultaneously and in parallel, and both sound pressure measurement data and load measurement data are recorded as time-series data. The measurement data and the load measurement data are linked on the time axis.

In the next step S3, first, the measurement data when the tire T runs over the projection is excluded from the sound pressure measurement data. Specifically, if the measured data measured by the load measuring device 22 while the vehicle is running includes a measured value equal to or greater than a predetermined reference value, the It is determined that the tire T had run over the protrusion at this time. The "predetermined reference value" is set in advance. Then, from the entire measurement data of the sound pressure, the portion judged to be the measurement data when the tire T was running over the protrusion is excluded.

Next, acoustic holography processing is performed based on the measurement data of the sound pressure after excluding the measurement data when the tire T was running over the protrusion. Acoustic holography processing uses an already established NAH (Near Field Acoustic Holography) method or the like. _{Briefly explained} based _on the image _diagram of FIG. From the inverse characteristic H ⁻¹ of the transfer function H, the sound pressure distribution p(x, y, 0) on the sound source surface is calculated. In this embodiment, the sound pressure distribution on the surface including the ground contact portion G of the tire T is obtained from the sound pressure distribution measured by the microphone array 12 . This sound pressure distribution can be obtained for sounds of all frequencies, but may be obtained only for sounds of a particular frequency of interest.

In the next sound source identification step S4, the portion having the highest sound pressure in the sound pressure distribution on the surface including the contact portion G of the tire T is identified as the noise source of that frequency. Any grooves or sipes in the tread surface, for example, are identified as sources of noise. The sound source may be specified by a person looking at the sound pressure distribution, or by the computer 18 . A designer of the tire T can change the design of the tread pattern of the tire T based on the result of specifying the sound source.

<About the effect of the embodiment>
According to this embodiment, the microphone array 12 as a noise measuring device is attached to the non-rotating portion that moves up and down together with the tire T. As shown in FIG. Therefore, the positional relationship between the microphone array 12 and the tires T does not change even if the vehicle accelerates, turns, or rides over a protrusion on the actual road surface S.

Further, it is detected that the tire T has run over the bump on the road surface S, and the sound pressure measurement data at the time of detection is excluded from the entire sound pressure measurement data. Therefore, the sound source is specified in a form in which the data of the sound (that is, noise) generated when the tire T runs over the bump on the road surface S is excluded.

For these reasons, according to the present embodiment, the noise source can be specified with high accuracy.

<Regarding a modified example of the embodiment>
Another noise measuring device may be used instead of the microphone array 12 of the above embodiment.

For example, at the position of the microphone array 12 in the above embodiment, a plurality of independent microphones are arbitrarily arranged instead of the microphone array 12, and these microphones simultaneously measure the sound pressure, thereby measuring the sound pressure with the microphone array 12. You may acquire the measurement data similar to time. Examples of microphones used in this case include probe microphones, 1/2, 1/4, or 1/8 inch microphones (i.e., measuring portion 1/2, 1/4 or 1/8 inch diameter) or MEMS (Micro-Electrical-Mechanical Systems) microphones.

Also, instead of the microphone array 12, a sound intensity microphone may be provided at the position of the microphone array 12 of the above embodiment. If an acoustic intensity microphone is used, the sound source is identified by known intensity mapping.

When a plurality of microphones or sound intensity microphones are used as the noise measuring device as in these modified examples, the noise measuring device is attached to the non-rotating portion that moves up and down with the tire in the same manner as in the above embodiment.

Also, instead of the load measuring device 22 of the above-described embodiment, another detector that detects when the tire has run over a bump on the road surface may be used. Such detectors are mounted on any part of the vehicle as in the above embodiments.

For example, a displacement sensor as a detector may be attached to a non-rotating portion that moves up and down with the tire, and the displacement sensor may continuously measure the distance from the road surface to the displacement sensor while the vehicle is running. When the tire rides over bumps on the road surface, the tire flexes, which changes the measured value of the displacement sensor. As a result, it is detected that the tires have run over bumps on the road surface.

Further, on the premise that the sound source probing methods of the above embodiments and modified examples are implemented, the running state and running location of the vehicle can be further detected and associated with measurement data obtained by a noise measuring device such as the microphone array 12. It is also possible to identify the relationship between the running state of the vehicle, the running location, and the source of the noise.

For example, while the vehicle is running, at the same time as measuring noise with a noise measuring instrument, the running state (for example, vehicle speed, vehicle acceleration, tire longitudinal force, tire torque, tire lateral force, tire slip angle, The turning state of the tires, or the steering angle) is measured. Since the noise measurement data and the driving condition measurement data are linked on the time axis, the sound source in the specific driving condition can be specified based on the noise measurement data in the specific driving condition. The acceleration of the vehicle can also be grasped based on the speed of the vehicle, the longitudinal force of the tires, the torque of the tires, and the like. Further, the turning state of the tires can be grasped based on the speed of the vehicle, the lateral force of the tires, the slip angle of the tires, the steering angle, and the like.

In another example, while the vehicle is running, the running position is continuously detected by the GPS at the same time as the noise is measured by the noise measuring device. Then, based on the measurement data of the noise when traveling on a specific road, the sound source when traveling on that road is identified. If the road surface condition of the road on which the vehicle has traveled is known, it is possible to identify the relationship between the road surface condition and the noise source.

B... Boundary between tire and rim, G... Contact portion, H... Half height position of contact side portion of tire, R... Rim, S... Road surface, T... Tire, 10... Sound source detection device, 11... Microphone Lower end of array 12... Microphone array 13... Small microphone 16... Acoustic holography device 18... Computer 20... Output device 22... Load measuring device 24... Fixing tool 27... Rotating member 29... Non-rotating Member 30 Lower arm 31 Knuckle 32 Damper fork 33 Wheel 34 Axle 35 Suspension

Claims (4)

In a sound source probing method in which noise generated from tires is measured outside a running vehicle and the source of the noise is specified based on the measurement data,
The noise is measured by a noise measuring device attached to the non-rotating part that moves up and down with the tire,
A detector mounted on any part of the vehicle detects that the tire has ridden over a bump in the road surface,
A sound source detection method, characterized in that data when a tire runs over a bump on the road surface is excluded from noise measurement data, and the data after the exclusion is used to identify the sound source. 2. The sound source investigation method according to claim 1, wherein the load measuring device as said detector for measuring the load applied to the tire detects that the tire has run over a bump on the road surface. 2. The sound source probing method according to claim 1, wherein the displacement sensor as said detector for measuring the distance to the road surface detects that the tires have run over the bumps on the road surface. 4. The lower end of the noise measuring device according to any one of claims 1 to 3, wherein the lower end of the tire is higher than half the height of the ground contact side portion of the tire and lower than the boundary between the tire and the rim at the contact side portion of the tire. Sound source probing method.

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