JP2022089633A - Tire sound radiation evaluation method - Google Patents

Abstract

To evaluate a contribution of oscillation on a tire surface to sound radiation generating from tires in a rolling motion.SOLUTION: An evaluation method of sound radiation from tires includes the steps of: obtaining a relationship between a sound at a sound source location and tire surface oscillation thereat from a signal of the sound at the sound source location when acoustically oscillating a tire surface standing still by the sound from the sound source, and a signal obtained by measuring the tire surface oscillation generating due to the acoustic oscillation at an oscillation measurement location; causing the tire to roll, and measuring the tire surface oscillation in a rolling motion at the oscillation measurement location, and measuring sound radiation from the tire in the rolling motion at the sound source location; obtaining a calculatory signal at a sound source location of the sound arising from the tire surface oscillation in the rolling motion from a signal of the tire surface oscillation in the rolling motion, and the relationship; and obtaining a ratio of the signal of the sound radiation from the tire in the rolling motion measured at the sound source position, and the calculatory signal at the sound source position of the sound arising from the tire surface oscillation in the rolling motion measured at the sound source position.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for evaluating tire radiation sound.

For example, as described in Patent Document 1, a radiated sound is generated from a tire rolling on a road surface. Radiated noise is noise inside and outside the vehicle, so it is required to reduce it. Causes of radiation noise include vibration of the tire surface (particularly the sidewall), resonance in the groove of the tire tread, contact and friction between the tire and the road surface, and the like.

Japanese Unexamined Patent Publication No. 2010-0368550

In order to take effective measures against radiated sound, it is necessary to clarify how much each of the above-mentioned causes contributes to radiated sound. However, the method has not been established until now.

Therefore, it is an object of the present invention to provide a method for evaluating the contribution of vibration on the tire surface to the radiated sound generated from a rolling tire.

（Ｑ（ｆ）^＊はＱ（ｆ）の複素共役）
を求める工程と、前記所定位置でタイヤを転動させ、転動中のタイヤ表面振動を前記振動測定位置において測定したときの振動のフーリエスペクトルｒ（ｆ）と、転動中のタイヤからの放射音を前記音源位置で測定したときの音圧のフーリエスペクトルｑ（ｆ）とを求め、２つのフーリエスペクトルｒ（ｆ）、ｑ（ｆ）のクロスパワースペクトル

（ｑ（ｆ）^＊はｑ（ｆ）の複素共役）
を求める工程と、前記伝達関数Ｈ_ＱＲ（ｆ）と前記クロスパワースペクトルＣ_ｑｒ（ｆ）とから、転動中のタイヤ表面振動に起因する音の前記音源位置での計算上のオートパワースペクトル

を求める工程と、前記音源位置で測定された転動中のタイヤからの放射音の音圧のオートパワースペクトル

と、転動中のタイヤ表面振動に起因する音の前記音源位置での計算上の前記オートパワースペクトルＣ_ＱＱ（ｆ）との周波数ｉのときの比

を求める工程とを含む。 The method for evaluating the tire radiation sound of the embodiment is the Fourier spectrum Q (f) of the sound pressure at the sound source position when the tire surface stationary at a predetermined position is acoustically vibrated by the sound from the sound source position, and the sound. From the Fourier spectrum R (f) of the vibration when the tire surface vibration generated by the vibration is measured at the vibration measurement position, the transfer function between the tire surface vibration and the sound source position.

(Q (f) ^* is the complex conjugate of Q (f))
The Fourier spectrum r (f) of the vibration when the tire is rolled at the predetermined position and the vibration on the tire surface during rolling is measured at the vibration measurement position, and the radiation from the rolling tire. The Fourier spectrum q (f) of the sound pressure when the sound is measured at the sound source position is obtained, and the cross power spectrum of the two Fourier spectra r (f) and q (f) is obtained.

(Q (f) ^* is the complex conjugate of q (f))
From the transfer function H _QR (f) and the cross power spectrum C _qr (f), the calculated auto power spectrum at the sound source position of the sound caused by the vibration of the tire surface during rolling.

And the auto power spectrum of the sound pressure of the radiated sound from the rolling tire measured at the sound source position.

The ratio of the sound caused by the vibration of the tire surface during rolling to the calculated auto power spectrum C _QQ (f) at the sound source position at the frequency i.

Includes the process of finding.

According to the above evaluation method, it is possible to evaluate the contribution of the vibration of the tire surface to the radiated sound generated from the rolling tire.

The figure which shows the arrangement of a measuring instrument and the like. The flowchart of the evaluation method of an embodiment.

The embodiment will be described with reference to the drawings. It should be noted that the embodiments described below are merely examples, and those appropriately modified without departing from the spirit of the present invention shall be included in the scope of the present invention.
1. 1. Arrangement of measuring instruments and the like The arrangement of pneumatic tires (hereinafter referred to as “tires”) and equipment in the present embodiment will be described. As shown in FIG. 1, a sound source position P and a vibration measurement position V are provided at positions in the axial direction of the tire T. A speaker 10 for generating sound is arranged at the sound source position P, and a laser Doppler vibrating meter 11 for measuring the vibration speed is arranged at the vibration measuring position V. Further, at the sound source position P, a microphone 12 for measuring sound pressure is also arranged adjacent to the speaker 10. The laser Doppler vibrometer 11 and the microphone 12 are connected to the analyzer 13. Further, the speaker 10 is connected to the control device 14, and the generation of sound is started and stopped by the control of the control device 14.

These tires and equipment are arranged in an anechoic chamber, a semi-anechoic chamber, or outdoors without a shield. Therefore, the method of this embodiment is performed in an anechoic chamber, a semi-anechoic chamber, or outdoors without a shield.

The sound generating portion of the speaker 10 and the detecting portion of the laser Doppler vibrometer 11 face the direction of the tire T. Therefore, the speaker 10 generates a sound toward the tire T, and the laser Doppler vibrometer 11 measures the vibration speed of the surface of the tire T (hereinafter referred to as “tire surface”). Note that FIG. 1 shows a state in which the sound generating part of the speaker 10 and the detecting part of the laser Doppler vibrometer 11 are facing the direction of the sidewall SW, and these generating parts and the detecting part are of the tire T. It may be facing the direction of another part.

The sound source position P is closer to the tire T than the vibration measurement position V. As a result, there is no obstacle between the speaker 10 and the tire T, and the sound generated from the speaker 10 reaches the tire T without being affected by the obstacle. Further, since the sound generated from the speaker 10 does not directly enter the detection unit of the laser Doppler vibrometer 11, the detection unit of the laser Doppler vibrometer 11 is less likely to shake and accurate measurement is possible.

The sound source position P is defined by, for example, the so-called JASO point (position at a height of 25 mm at a point 1 m away from the center of contact with the tire) in the bench test and the international standard (ECE R117-02) related to the noise regulation of a single tire. It is the position of the microphone when measuring the outside noise.

The tire T is attached to a general testing machine. The testing machine has a rotating road surface R, and the tire T is in contact with the ground on the rotating road surface R. The rotating road surface R starts and stops rotating under the control of the control device 14. When the rotating road surface R rotates, the tire T rolls. However, the tire T rolls in a fixed position even during rolling and does not move back and forth. The rotating road surface R is appropriately selected from a resin road surface, an asphalt road surface, a concrete road surface, and the like, and the surface roughness thereof is also appropriately set.

The tire T is rim-assembled on a predetermined rim, a predetermined internal pressure is applied, and a predetermined load is applied. The conditions of internal pressure and load are not limited.

In the first measurement described later, the rotating road surface R does not rotate, and the tire T is held in a stationary state. When a sound is generated from the speaker 10 in that state, the sound reaches the tire T in a stationary state and the tire surface vibrates. That is, the speaker 10 acoustically vibrates the tire surface. The laser Doppler vibrometer 11 measures the vibration speed. Further, the microphone 12 measures the sound pressure of the sound generated from the speaker 10. The measurement data of the laser Doppler vibrometer 11 and the microphone 12 are sent to the analysis device 13.

Further, in the second measurement described later, the rotating road surface R rotates and the tire T rolls. When the tire T rolls, the tire surface vibrates. In addition to the vibration of the tire surface, resonance in the groove of the tread and contact and friction between the tire T and the rotating road surface R also cause radiation noise from the tire T. The microphone 12 measures the sound pressure of the radiated sound from the tire T, and the laser Doppler vibrating meter 11 measures the vibration speed of the tire surface. The measurement data of the microphone 12 and the laser Doppler vibrometer 11 are sent to the analysis device 13.

The tire T is in the same predetermined position (position on the rotating road surface R) during the first measurement and the second measurement. Further, the positions of the laser Doppler vibrometer 11 and the microphone 12 are also the same between the first measurement and the second measurement.

Further, the analysis device 13 has a processing device and a storage device, and the processing device reads and executes the program stored in the storage device to perform the calculation of the present embodiment.

2. 2. Evaluation Method of Tire Radiation Sound As shown in FIG. 2, the method of the present embodiment includes steps S1 to S6.

In step S1, the stationary tire T is acoustically vibrated by the sound from the speaker 10 at the sound source position P, the sound is measured at the sound source position P, and the tire surface vibration is measured at the vibration measurement position V. It is a process.

Step S2 is a second measurement step of rolling the tire T to measure the radiated sound from the tire T at the sound source position P and measuring the tire surface vibration at the vibration measurement position V.

Step S3 is a step of obtaining the relationship between the sound pressure at the sound source position P and the tire surface vibration as a transmission function from the Fourier spectrum of the sound pressure obtained in the first measurement and the Fourier spectrum of the tire surface vibration.

Step S4 is a step of obtaining a cross power spectrum based on the Fourier spectrum of the sound pressure obtained in the second measurement and the Fourier spectrum of the tire surface vibration.

Step S5 is a step of obtaining an auto power spectrum at the sound source position P of the sound pressure caused by the tire surface vibration at the time of the second measurement based on the transfer function obtained in step S3 and the cross power spectrum obtained in step S4. Is.

The step S6 is rolling with respect to the radiated sound generated from the rolling tire T based on the auto power spectrum of the sound pressure of the radiated sound measured at the time of the second measurement and the auto power spectrum obtained in the step S5. This is a process for obtaining the contribution rate of sound caused by the vibration of the tire surface.

Hereinafter, steps S1 to S6 will be specifically described.

(1) Step S1
In the first measurement step S1, the control device 14 generates a sound from the speaker 10 toward the stationary tire T. The tire surface vibrates due to the sound from the speaker 10. While the sound is generated from the speaker 10 and the tire surface is vibrating, the microphone 12 measures the sound pressure of the sound generated from the speaker 10, and in parallel with this, the laser Doppler vibrometer 11 vibrates the tire surface. To measure. Each measurement data is sent to the analysis device 13.

(2) Step S2
In the second measurement step S2, the control device 14 rotates the rotating road surface R to roll the tire T. When the tire T rolls, a radiating sound is generated from the tire T, and the tire surface vibrates. While the tire T is rolling, the microphone 12 measures the sound pressure of the radiated sound from the tire T, and in parallel with this, the laser Doppler vibrometer 11 measures the vibration velocity of the tire surface. Each measurement data is sent to the analysis device 13.

(3) Step S3
In step S3 for obtaining the transfer function, first, the analyzer 13 measured the Fourier spectrum R (f) of the vibration velocity of the tire surface measured by the laser Doppler vibrometer 11 at the time of the first measurement and the microphone 12 at the time of the first measurement. The Fourier spectrum Q (f) of the sound pressure is obtained. Note that f is a frequency. Next, the analysis device 13 obtains the transfer function H _QR (f) as follows.

ここで、Ｑ（ｆ）^＊はＱ（ｆ）の複素共役である。また、Ｃ_ＱＱ（ｆ）はマイクロホン１２で測定した音圧のオートパワースペクトルで、Ｃ_ＱＲ（ｆ）は前記振動速度の前記音圧に対するクロスパワースペクトルである。ただしここでのオートパワースペクトルやクロスパワースペクトルは第１測定時のものである。

Here, Q (f) ^* is the complex conjugate of Q (f). Further, C _QQ (f) is an auto power spectrum of the sound pressure measured by the microphone 12, and C _QR (f) is a cross power spectrum of the vibration velocity with respect to the sound pressure. However, the auto power spectrum and the cross power spectrum here are those at the time of the first measurement.

As can be seen from the equation (I), the transmission function H _QR (f) obtained in this way is the relationship between the sound pressure measured at the sound source position P and the vibration velocity of the tire surface measured at the vibration measurement position V. Represents.

As can be seen from the equation (I), the transmission function H _QR (f) contains information on the phase relationship between the vibration velocity of the tire surface measured by the laser Doppler vibrometer 11 and the sound pressure measured by the microphone 12. It has been.

(4) Step S4
In the next step S4, the analyzer 13 has a Fourier spectrum r (f) of the vibration velocity of the tire surface measured at the time of the second measurement and a Fourier spectrum q (f) of the sound pressure measured by the microphone 12 at the time of the second measurement. Ask for. Next, the analysis device 13 obtains the cross power spectra C _qr (f) of these Fourier spectra r (f) and q (f) as follows.

ここで、ｑ（ｆ）^＊はｑ（ｆ）の複素共役である。

Here, q (f) ^* is the complex conjugate of q (f).

(5) Step S5
In the next step S5, the analyzer 13 obtains the transfer function H _QR (f) obtained in the step S3 and the cross power spectrum C _qr (f) obtained in the step S4 at the time of the second measurement (rolling of the tire T). The auto power spectrum C _QQ (f) at the sound source position P of the sound pressure caused by the vibration of the tire surface during (moving) is obtained. Specifically, the analysis device 13 obtains the auto power spectrum C _QQ (f) by the following equation.

なお、この工程Ｓ５で求まるオートパワースペクトルＣ_ＱＱ（ｆ）は、タイヤＴの転動中のタイヤ表面の振動に起因する音圧のオートパワースペクトルなので、式（Ｉ）に記載のオートパワースペクトルＣ_ＱＱ（ｆ）（すなわち、静止中のタイヤＴを音響加振したときの音のオートパワースペクトル）と大きさが異なる。しかし、式（Ｉ）と式（III）のオートパワースペクトルＣ_ＱＱ（ｆ）は、タイヤ表面の振動と関係する、音源位置Ｐでの音圧のオートパワースペクトルであるという点で同じである。

Since the auto power spectrum C _QQ (f) obtained in this step S5 is the auto power spectrum of the sound pressure caused by the vibration of the tire surface during the rolling of the tire T, the auto power spectrum C described in the formula (I). The magnitude is different from _QQ (f) (that is, the auto power spectrum of the sound when the stationary tire T is acoustically vibrated). However, the autopower spectra _CQQ (f) of the equations (I) and (III) are the same in that they are autopower spectra of the sound pressure at the sound source position P, which is related to the vibration of the tire surface.

Further, as described above, the transmission function _HQR (f) includes information on the phase relationship between the vibration velocity of the tire surface measured by the laser Doppler vibrometer 11 at the time of the first measurement and the sound pressure measured by the microphone 12. Therefore, the auto power spectrum C _QQ (f) obtained by Eq. (III) reflects the phase relationship.

(5) Step S6
In the next step S6, first, the analyzer 13 first measures the autopower spectrum C _qq (f) of the sound pressure of the sound radiated from the tire T measured at the sound source position P at the time of the second measurement (during the rolling of the tire T). ). This auto power spectrum C _qq (f) is obtained as follows using the Fourier spectrum q (f) of the sound pressure measured at the sound source position P at the time of the second measurement and its complex conjugate q (f) ^* . ..

このオートパワースペクトルＣ_ｑｑ（ｆ）は、タイヤ表面の振動に起因する音と、それ以外のことに起因する音とが合わさった音圧のオートパワースペクトルである。

This auto power spectrum C _qq (f) is an auto power spectrum of sound pressure in which a sound caused by vibration of the tire surface and a sound caused by other factors are combined.

Next, the analyzer 13 has an auto power spectrum C _QQ (f) obtained in step S5 for a specific frequency i (that is, an auto power spectrum C _QQ for calculating the sound pressure generated from the vibration of the tire surface during rolling. The ratio of the sound pressure actually measured during the rolling of the tire T to the above-mentioned auto power spectrum C _qq (f) in (f)) is obtained. That is, the analysis device 13 obtains the following σi for a specific frequency i.

ここで、上記の通りＣ_ＱＱ（ｆ）には測定データの位相関係が反映されているので、σｉにもその位相関係が反映されている。

Here, since the phase relationship of the measurement data is reflected in C _QQ (f) as described above, the phase relationship is also reflected in σi.

The analysis device 13 obtains such σi for one or more frequencies i. The σi thus obtained represents the contribution ratio of the sound of the frequency i caused by the vibration of the tire surface to the radiated sound of the frequency i generated from the tire T during rolling.

3. 3. Effect of the Embodiment As described above, in the steps S1 and S3, the Fourier spectrum Q (f) of the sound pressure at the sound source position P when the stationary tire surface is acoustically vibrated by the sound from the sound source position P. , The sound pressure at the sound source position P and the tire measured at the vibration measurement position V based on the Fourier spectrum R (f) obtained by measuring the tire surface vibration generated by the acoustic vibration at the vibration measurement position V. The transfer function H _QR (f) can be obtained as the relationship with the surface vibration.

Further, separately from the step S1, a step S2 is carried out in which the vibration of the tire surface during rolling is measured at the vibration measurement position V and the radiated sound from the rolling tire T is measured at the sound source position P. Using the results, in step S4, the Fourier spectrum r (f) of the tire surface vibration measured at the vibration measurement position V during the tire rolling and the Fourier spectrum q of the sound pressure measured at the sound source position P ( The cross power spectrum C _qr (f) with f) can be obtained.

Further, from the transfer function H _QR (f) obtained in step S3 and the cross power spectrum C _qr (f) obtained in step S4 in step S5, the sound source position of the sound caused by the vibration of the tire surface during rolling. The autopower spectrum C _QQ (f) of the calculated sound pressure at P can be obtained.

Then, in step S6, the auto power spectrum C _qq (f) of the sound pressure of the radiated sound from the rolling tire T measured at the sound source position P and the sound source of the sound caused by the tire surface vibration during rolling. The ratio σi with the calculated _CQQ (f) at the position P can be obtained. The ratio σi is the contribution ratio of the sound caused by the tire surface vibration to the radiated sound generated from the tire T during rolling.

In this way, the contribution of vibration on the tire surface to the radiated sound generated from the rolling tire T can be evaluated. If such an evaluation can be made, effective measures can be taken against the radiated sound generated from the rolling tire T.

Further, since the phase of the measurement data is reflected in the equations (I) to (V) until the ratio σi is obtained, the contribution of the vibration of the tire surface to the radiated sound generated from the tire T during rolling. Can be evaluated accurately.

4. Modification example A plurality of modification examples with respect to the above embodiment will be described. One of a plurality of modified examples may be applied to the above embodiment, or any two or more of the plurality of modified examples may be applied in combination. In addition to the following modification examples, various changes are possible.

(1) Change example 1
The step S1 of the first measurement may be replaced with a simulation using a computer. That is, a simulation may be performed in which the tire model is vibrated by the sound from the sound source and the acceleration of the vibration is acquired. Using the result, the transfer function can be obtained in the same manner as in step S3.

(2) Change example 2
The means for measuring the vibration of the tire surface is not limited to the above-mentioned laser Doppler vibrometer 11. As a means for measuring the vibration of the tire surface, a contact type or non-contact type displacement meter, a speedometer, an accelerometer or the like can be used. For example, the vibration of the tire surface may be measured by fixing the accelerometer to the tire surface.

(3) Change example 3
The above-mentioned first measurement and second measurement may be performed with the tire T attached to the vehicle body.

(4) Change example 4
As the measurement of the sound generated from the speaker 10 at the time of the first measurement and the measurement of the radiated sound generated from the tire T at the time of the second measurement, the particle velocity may be measured instead of the sound pressure measurement.

(5) Change example 5
At the time of the first measurement, instead of generating sound from the speaker 10 and measuring the sound pressure of the sound with the microphone 12, a particle velocity meter having a known volume may be arranged in front of the speaker 10 to measure the volume velocity.

R ... rotating road surface, T ... tire, SW ... sidewall, P ... sound source position, V ... vibration measurement position, 10 ... speaker, 11 ... laser Doppler vibrometer, 12 ... microphone, 13 ... analysis device, 14 ... control device

Claims (2)

Vibration measurement of the Fourier spectrum Q (f) of the sound pressure at the sound source position when the tire surface stationary at a predetermined position is acoustically vibrated by the sound from the sound source position and the tire surface vibration generated by the acoustic vibration. From the Fourier spectrum R (f) of the vibration measured at the position, the transfer function between the tire surface vibration and the sound source position.

(Q (f) ^* is the complex conjugate of Q (f))
And the process of finding
The Fourier spectrum r (f) of the vibration when the tire is rolled at the predetermined position and the vibration on the tire surface during rolling is measured at the vibration measurement position, and the radiated sound from the rolling tire are measured at the sound source position. The Fourier spectrum q (f) of the sound pressure measured in 1) is obtained, and the cross power spectrum of the two Fourier spectra r (f) and q (f) is obtained.

(Q (f) ^* is the complex conjugate of q (f))
And the process of finding
From the transfer function H _QR (f) and the cross power spectrum C _qr (f), the auto power spectrum of the calculated sound pressure at the sound source position of the sound caused by the vibration of the tire surface during rolling.

And the process of finding
Autopower spectrum of sound pressure of radiated sound from rolling tires measured at the sound source position

The ratio of the sound caused by the vibration of the tire surface during rolling to the calculated auto power spectrum C _QQ (f) at the sound source position at the frequency i.

And the process of finding
How to evaluate the radiated sound from the tire, including. The evaluation method according to claim 1, wherein the tire surface is acoustically vibrated by the sound from the speaker arranged at the sound source position, and the tire surface vibration is measured by the device arranged at the vibration measuring position.

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