JP2017166995A - Evaluation method of noise performance of tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaluation method of noise performance of a tire capable of being accurately and quantitatively performed.SOLUTION: A method of evaluating the noise performance of a tire includes: a process S0 of collecting noise during tire travel; a first analysis process S1 of extracting first noise included in a first frequency band from the collected noise; a second analysis process S2 of calculating the frequency spectrum of the first noise by frequency analysis; a third analysis process S3 of calculating the total value of sound pressure levels in a second frequency band from the frequency spectrum of the first noise; and an evaluation process S4 of evaluating the noise on the basis of the magnitude of the total value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method capable of quantitatively evaluating the noise performance of a tire.

  Conventionally, the noise performance of a tire is often evaluated by sensory performance (see, for example, Patent Document 1 below). In particular, among tire noises, a roaring sound with a sense of variation, a low-pitched sound with a feeling of pressure, and the like tend to be evaluated by sensuality. However, since such sensory evaluation is based on the subjectivity of the evaluator, there is a problem that the result cannot be quantitatively evaluated.

JP 2007-309652 A

  The present invention has been devised in view of the above circumstances, and the tire noise performance that can be carried out accurately and quantitatively based on the evaluation of noise based on the frequency spectrum of noise obtained by frequency analysis. The main purpose is to provide an evaluation method.

  The present invention is a method for evaluating the noise performance of a tire, the step of collecting noise during tire running, and a first analysis for extracting first noise included in a first frequency band from the collected noise. And a second analysis step of calculating a frequency spectrum of the first noise by frequency analysis, and a third analysis step of calculating a total value of sound pressure levels in a second frequency band from the frequency spectrum of the first noise. And an evaluation step for evaluating the noise based on the magnitude of the total value.

  In the tire noise performance evaluation method of the present invention, it is preferable that the first frequency band includes a band of at least ± 5 Hz centered on any of 40 Hz, 80 Hz, or 250 Hz.

  In the tire noise performance evaluation method of the present invention, the first frequency band is preferably a band of ± 10 Hz centered on any of 40 Hz, 80 Hz, or 250 Hz.

  In the tire noise performance evaluation method of the present invention, it is desirable that the second frequency band is at least ± 2 Hz centered on 4 Hz.

  The present invention relates to a method for evaluating the noise performance of a tire, the step of collecting noise during tire traveling, and the first analysis step of extracting the first noise included in the first frequency band from the collected noise. A second analysis step of calculating a frequency spectrum of the first noise by frequency analysis, a third analysis step of calculating a total value of sound pressure levels in the second frequency band from the frequency spectrum of the first noise, And an evaluation step of evaluating noise based on the magnitude of the total value.

  In the tire noise performance evaluation method of the present invention, the first noise included in the first frequency band is extracted in the first analysis step. For this reason, by determining the first frequency band according to the type of noise to be evaluated, it is possible to extract the noise necessary for the evaluation, and thus to accurately evaluate the noise performance of the tire.

  The evaluation method of the present invention calculates a total value of sound pressure levels in the second frequency band from the frequency spectrum of the first noise, and evaluates the noise based on the magnitude of the total value. Such an evaluation method can accurately and quantitatively evaluate beat sounds, bass sounds, and the like that have been conventionally evaluated by sensuality.

It is a flowchart which shows one Embodiment of the evaluation method of the noise performance of the tire of this invention. FIG. 3 is a side view of a test vehicle for collecting noise during tire travel. (A) is a graph which shows the noise level of the 1st frequency band obtained at the 1st analysis process, (b) is a graph which expanded a part of graph of (a). (A) is a graph showing the frequency spectrum of the 1st noise of FIG.3 (b), (b) is the graph which expanded a part of graph of (a). (A) is a graph which shows the result of the evaluation method of this embodiment obtained by Test 1, and (b) is a graph which shows the correlation with the evaluation method of this embodiment, and sensory evaluation.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a flowchart showing an embodiment of a method for evaluating the noise performance of a tire according to the present invention. As shown in FIG. 1, the present embodiment includes a step S0 for collecting noise during tire traveling, a first analysis step S1, a second analysis step S2, and a third analysis step for analyzing the collected noise. S3 and evaluation process S4 which evaluates noise based on these analyzes are included. Hereinafter, each process will be described in detail.

<Step S0 for collecting noise during tire running>
In step S0 for collecting noise during tire running, for example, a test vehicle equipped with a test tire is run, and the noise at that time is collected. However, this process S0 is not limited to such an aspect.

  FIG. 2 shows a side view of the test vehicle 1 for collecting noise during tire travel. As shown in FIG. 2, the test vehicle 1 of the present embodiment is a passenger car, and test tires 2 are mounted on all the wheels. A microphone 3 for collecting noise is provided in the test vehicle 1.

  The microphone 3 is preferably provided near the driver's seat, for example. As a more desirable mode, the microphone 3 of the present embodiment is provided on the upper right side of the driver's seat. Such a position of the microphone 3 corresponds to a position in the vicinity of the right ear of the driver who is seated, and it is possible to collect a sound that approximates the noise felt by the driver during normal driving. However, the position of the microphone 3 is not limited to such a mode. The noise collected by the microphone 3 is stored as electronic data, for example.

  Examples of conditions for collecting noise include road surface conditions and travel speed conditions. Various types are adopted depending on the type of noise to be evaluated.

  As the road surface condition, the test road surface G of the present embodiment is, for example, a flat and non-gradient dry asphalt road surface. Further, as the traveling speed condition, in this embodiment, for example, noise is collected when the vehicle travels straight at a speed of 30 to 60 km / h.

  For example, it is desirable to collect the noise a plurality of times under the same conditions. In the present embodiment, the noise is collected at least three times. Thereby, the influence of the measurement error can be reduced.

<First analysis step S1>
The noise collected in the noise collection step S0 is a combination of various sounds with different frequencies. In this step S1, the first noise included in the first frequency band is extracted from the collected noise using a bandpass filter. A known bandpass filter is preferably used.

  The first frequency band is determined according to the type of noise to be evaluated. Generally, it is known that the frequency band of tire noise varies depending on the cause of occurrence. Of the tire noise, the center of the low frequency band that gives the passenger a feeling of pressure is about 40 Hz. The center of the frequency band of the tire beat sound is about 80 Hz. The center of the frequency band of the cavity resonance sound of the tire is about 250 Hz. In order to evaluate these noises, it is desirable that the center of the first frequency band is, for example, any one of 40 Hz, 80 Hz, and 250 Hz.

  In order to accurately evaluate the noise performance, the first frequency band can include, for example, a band of at least ± 5 Hz, more preferably ± 10 Hz, centered on any of the above frequencies. The first frequency band of the present embodiment is, for example, a ± 10 Hz band centered on 80 Hz, that is, 70 to 90 Hz. However, the first frequency band is not limited to such a range and can be appropriately changed as necessary.

  FIGS. 3A and 3B show graphs showing the noise level in the first frequency band obtained in the first analysis step. In the graphs of FIGS. 3A and 3B, the horizontal axis represents time t (s), and the vertical axis represents noise level NL (dB (A)). The graph of FIG. 3A represents the magnitude of the noise level in the entire range of the time (7 seconds) when the noise is collected. FIG. 3B shows an enlarged range A1 of t = 0 to 0.5 (s) in the graph of FIG.

<Second analysis step S2>
In the second analysis step S2, a frequency spectrum is calculated for the frequency of the temporal fluctuation of the noise level of the first noise. In step S2, the range of the first noise for calculating the frequency spectrum is determined. As the first noise, for example, as shown in FIG. 3A, the entire range of time when the noise is collected may be selected, or a part of them may be used. In the present embodiment, for example, as shown in FIG. 3B, data in the range of t = 0 to 0.5 (s) is used among all the data of the first noise.

  4 (a) and 4 (b) show graphs representing the frequency spectrum of the first noise in FIG. 3 (b). The graphs shown in FIGS. 4A and 4B are obtained by frequency analysis of the graph of FIG. In the present embodiment, for example, FFT processing is employed as frequency analysis. 4A and 4B, the horizontal axis represents the noise level frequency fn (Hz), and the vertical axis represents the noise power spectral density Pn (dB2 / Hz). FIG. 4A is a graph showing the entire frequency spectrum, and FIG. 4B is an enlarged view of the range A2 where the frequency fn is 0 to 10 (Hz) in the graph of FIG. 4A. It is.

The FFT processing can be performed using, for example, an FFT analyzer. In order to obtain high resolution, in the FFT processing of this embodiment, for example, the number of lines is 1600 or more, the overlap is 80% or more, and the window function is processed by hanning. However, it is not limited to such conditions, and each condition can be changed as needed.

<Third analysis step S3>
As a result of various experiments, the inventors have summed up the sound pressure levels in a specific frequency band in the frequency spectrum of the first noise, so that noises that have been evaluated by sensuality in the past, such as roaring sounds and bass sounds, can be obtained. It was found that it can be evaluated accurately and quantitatively. For this reason, in 3rd analysis process S3, the total value of the sound pressure level of the 2nd frequency band according to the objective is calculated from the frequency spectrum of 1st noise.

  Further, the inventors of the present invention have a sound pressure level in the band of 2 to 6 Hz that is easy for humans to hear in the frequency spectrum of the first noise. I found out that I can do it. For this reason, it is desirable that the second frequency band is, for example, a band of at least ± 2 Hz centered on 4 Hz. However, the second frequency band is not limited to such a range, and can be determined in various ranges according to the type of noise to be evaluated.

<Evaluation process S4>
In the evaluation step S4, noise is evaluated based on the total value of the sound pressure levels in the second frequency band obtained in the third analysis step S3. Such an evaluation method can accurately and quantitatively evaluate beat sounds, bass sounds, and the like that have been conventionally evaluated by sensuality.

Next, the effect of this invention is demonstrated based on an experimental result. The following test vehicles equipped with the following test tires were used, and three types of sample noise were collected. Each noise was collected by changing the internal pressure of the tire in the following three stages.
Tire size: 195 / 65R15
Test vehicle: 1600cc displacement, front-wheel drive vehicle
Test vehicle running speed: 45km / h
Tire internal pressure: 180 kPa, 230 kPa, 280 kPa
Road surface: flat and non-gradient dry asphalt road surface

For each noise sample, both the conventional sensory evaluation and the evaluation by the method of the present invention were performed in the following Tests 1 to 3, and the evaluation results were compared. In addition, each score of sensory evaluation in each test is an average value of scores by five evaluators.
Test 1: Evaluation of beat sound Test 2: Evaluation of bass Test 3: Evaluation of cavity resonance

<Test 1: Evaluation of roaring sound>
Sensory evaluation was performed on the roaring sound with a sense of variation included in each sample noise. The sensory evaluation is a score where the beat sound included in the noise (sample 3) when the tire internal pressure is 280 kPa is 6.0 points, and the larger the value, the greater the beat sound.

For each noise, the evaluation method of the present invention was performed under the following conditions, and the total value of the sound pressure levels in the second frequency band was calculated.
First frequency band: 70 to 90 Hz
Range of frequency analysis of the first noise: t = 0 to 0.5 s
Second frequency band: 2 to 6 Hz
The specific conditions for the FFT processing are as follows.
Microphone used: Bruel & Kjar 4162-A
Analyzer: Bruel & Kjar Type3560
Usage analysis software: Bruel & Kjar Type7780,7781
Number of FFT processing lines: 1600
FFT processing overlap: 80%
Window function of FFT processing: Hanning Test results are shown in Table 1.

  In general, it is known that the beat sound increases as the tire internal pressure increases. As a result of Test 1, as shown in FIG. 5 (a), the evaluation method of the present invention also obtained a result consistent with the above findings. Further, as shown in FIG. 5B, the correlation coefficient between the sensory evaluation and the evaluation method of the present invention is 0.93, and the evaluation method of the present invention is high in sensory evaluation. It was confirmed that the correlation and the evaluation of the beat sound can be quantitatively evaluated.

<Test 2: Bass evaluation>
Sensory evaluation was performed on the low-pitched sounds included in each sample noise. The sensory evaluation is a score in which the low tone included in the noise of the sample 3 is 6.0 points, and the larger the numerical value, the higher the bass.

For each noise, the tire noise performance evaluation method of the present invention was performed under the following conditions, and the total value of the sound pressure levels in the second frequency band was calculated. The conditions for the FFT processing are the same as in Test 1.
First frequency band: 30-50Hz
Range of frequency analysis of the first noise: t = 0 to 0.5 s
Second frequency band: 2 to 6 Hz
The test results are shown in Table 2.

  As a result of Test 2, the correlation coefficient between the sensory evaluation and the method of the present invention is 0.93 for the evaluation of bass, and the evaluation method of the present invention has a high correlation with the sensory evaluation. That is, it was confirmed that the evaluation method of the present invention can accurately and quantitatively evaluate bass.

<Test 3: Evaluation of cavity resonance sound>
Sensory evaluation was performed on the cavity resonance contained in each sample noise. The sensory evaluation is a score that sets the cavity resonance included in the noise of the sample 3 to 6.0, and the larger the value, the greater the cavity resonance.

For each noise, the tire noise performance evaluation method of the present invention was performed under the following conditions, and the total value of the sound pressure levels in the second frequency band was calculated. The conditions for the FFT processing are the same as in Test 1.
First frequency band: 240-260 Hz
Range of frequency analysis of the first noise: t = 0 to 0.5 s
Second frequency band: 2 to 6 Hz
The test results are shown in Table 3.

  As a result of Test 3, the correlation coefficient between the sensory evaluation and the evaluation method of the present invention is 0.94 for the evaluation of the cavity resonance sound, and the evaluation method of the present invention has a high correlation with the sensory evaluation. That is, it was confirmed that the evaluation method of the present invention can accurately and quantitatively evaluate the cavity resonance sound.

  As a result of tests 1 to 3, it has been confirmed that the noise performance evaluation method of the tire of the present invention can accurately and quantitatively evaluate various noises that have been conventionally evaluated by sensuality.

  As described above, the embodiment of the method for evaluating the noise performance of the tire according to the present invention has been described in detail. However, the present invention is not limited to the above-described specific embodiment, and can be implemented in various forms. Can be done.

S0 Process for collecting noise during tire running S1 First analysis process S2 Second analysis process S3 Third analysis process S4 Evaluation process

Claims (4)

A method for evaluating the noise performance of a tire,
A process of collecting noise during tire travel;
A first analysis step of extracting a first noise included in a first frequency band from the collected noise;
A second analysis step of calculating a frequency spectrum of the first noise by frequency analysis;
A third analysis step of calculating a total value of sound pressure levels in the second frequency band from the frequency spectrum of the first noise;
An evaluation step of evaluating the noise based on the magnitude of the total value.   The tire noise performance evaluation method according to claim 1, wherein the first frequency band includes a band of at least ± 5 Hz centered around 40 Hz, 80 Hz, or 250 Hz.   3. The method for evaluating a tire noise performance according to claim 1, wherein the first frequency band is a band of ± 10 Hz centering on any of 40 Hz, 80 Hz, or 250 Hz.   The tire frequency performance evaluation method according to any one of claims 1 to 3, wherein the second frequency band is a band of at least ± 2 Hz centered on 4 Hz.

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