The object of this paper is to estimation of noise reduction effect of road noise by operating condition due to tire noise regulation. A prepare the countermeasure of the noise reduction according to collect tire/road noise data under various influencing factors by using the tire test method. To accomplish the object : A automotive is used as a test platform to test tire/road noise by changing different types of tires and using the On-Board Sound Intensity test system. The influence of inflation pressure, road, load, speed and pattern type on tire/road noise is compared and analyzed. At the same time, the mechanism of tire/road noise is analyzed, which provides an experimental basis for tire noise reduction.

PURPOSES : Exposed aggregate concrete pavements have been adopted in several countries because of their advantages of pavement texture characteristics, which can produce low tire-pavement noise and higher load-carrying capacities. The magnitude of tire-pavement noise greatly depends on the wavelength of pavement texture. The wavelength of exposed aggregate concrete pavement can be controlled with maximum sizing and by controlling the amount of coarse aggregates in the concrete mixture. In this study, the maximum size and the amount of coarse aggregate in the exposed aggregate concrete pavement are investigated to produce equal levels of wavelength in the asphalt pavement. METHODS: A simple method to measure the average wavelength of pavement texture is introduced. Subsequently, the average wavelength of typical asphalt pavement is investigated. A set of mixture designs of exposed aggregate concrete with three maximum-sized coarse aggregates, and three amounts of coarse aggregate are used. The average wavelengths are measured to find the mixture design needed to produce equal levels of wavelength as typical asphalt pavement. RESULTS : With a cement content of 420 kg/m3 and fine aggregate modulus of 30%, the number of exposed aggregates was 48, and the shortest texture depth provided a wavelength of 4.2 mm. According to the number of exposed aggregates, the exposed aggregate concrete pavement could be rendered low-noise, because its wavelength was similar to that of asphalt pavement ranging from 3.9 to 4.4 mm. CONCLUSIONS : Selection of appropriate maximum sizes and the amount of coarse aggregates for exposed aggregate concrete pavement can produce a wavelength texture closely resembling that of asphalt pavement. Therefore, the noise level of exposed aggregate concrete pavement can be reduced with an appropriate maximum size and the amount of coarse aggregates are employed.

The bending exercises of radial tire is one of the most important structural properties of the sidewall relating to ride and road noise of automobiles. The frequency band analysis is more useful for analyzing tire road noise due to property change of tread and sidewall. In this paper, the vertical stiffness and lateral stiffness of tire which have a various tread and sidewall is measured and the road noise is measured about same road condition. Furthermore, we investigated the effect on the structure of the tire tread and sidewall for the sound pressure level.

Among many potential problems associated with automobiles, the problem regarded as most sensitive and important to the customers is the automobile’s quietness. In particular, because the trend toward the high-performance automobiles is increasing, the quietness should be considered reflecting the increasing demand of the customers for the comfort of automobile ride. Road noise is the low-frequency range in the region of 20Hz to 350Hz, generated when the tires are making contacts with the rough road surface while the automobile is running, in which the noises are resonating within the passenger compartment or with the automobile suspension. In this research, among the factors related to the road noise, the influencing factors associated with the suspension and the tire design were investigated. In particular, among the tire design factors, the structure and the rubber material were investigated as the influencing factors, and for the investigative purpose, experimental tires were manufactured and road noise evaluations were conducted thorough actual feeling tests. Then the test results and correlations were analyzed using the 6-Sigma statistical method. Results from this study shows that, among the tire design factors, the apex is the most influencing factor, in which the height of the apex is the key. The influential factors were found out to be apex height, belt angle, and tread hardness, in that order, and when the suspension is of a same kind, the tendency of the road noise was found to be similar.

PURPOSES : The purpose of this study is to eliminate the noise of the vehicle after measuring the friction noise obtained from the NCPX (Noble Close ProXimity) method. The pure friction noise between the tire and road pavement could be determined from filtering the compositeness of sound and the influence of the vehicle noise. METHODS: The noise magnitude could be determined by analyzing the sound pressure level (SPL) and sound power level (PWL) along with the noise frequency of a FFT (Fast Fourier Transform) analysis as well as CPB (Constant Percentage Bandwidth) analysis. RESULTS: When the test for measuring the friction noise originated somewhere between tire and road pavement is performed with NCPX method, it must be fulfilled by attaching the surface microphone near the tire. In this condition, the surface microphone can measure the friction noise occurred at between tire and pavement, the chassis noise from the engine and power transfer units, the fluctuating aerodynamic noise, and the turbulence noise directly affected to the surface microphone. By using the NCPX method, the noise occurred at the vehicle must be eliminated for measuring the friction noise between tire and pavement from the traffic noise. CONCLUSIONS: The vehicle's testing engine noise depends on the vehicle and road types. The effect of vehicle's engine noise is less than the friction noise occurred at between tire and pavement at less than 1% effect.

Among many potential problems associated with passenger cars, the problem regarded as most sensitive and important to the customers is the passenger car’s quietness. In particular, because the trend toward the high-performance passenger cars is increasing, the quietness should be considered reflecting the increasing demand of the customers for the comfort of passenger car ride. Road noises are of low-frequency in the region of 20Hz to 350Hz, generated when the tires are making contacts with the rough road surface while the passenger car is running, in which the noises are resonating within the passenger compartment or with the passenger car suspension. In this research, among the factors related to the road noises, the influencing factors associated with the suspension and the tire design were investigated. In particular, among the tire design factors, the structure and the rubber material were investigated as the influencing factors, and for the investigative purpose, experimental tires were manufactured and road noise evaluations were conducted thorough actual feeling tests. Then the test results and correlations were analyzed using the 6-Sigma statistical method.

Tire manufactures have dealt with noise problem by varying the pitch of the tread. The various formulas for the variations are generally determined differently, however. Often these variations are based on a combination of trial and error, intuition, and economics. Some manufactures have models and analogs to test tread patterns and their variations. These efforts, however practical, do not determine the best variation beforehand or guarantee the best results. For this reason it was felt that a general mathematical approach for determining the best variation was needed. Moreover, the method should be completely general, easy to use, and sufficiently accurate. This paper discusses a mathematical method called Mechanical Frequency Modulation(MFM) which meets the above requirements. Thus, MFM pertains to computing an irregular time sequence of events so that the resulting excitation spectrum is shaped to a preferred form. The first part of this paper treats the theoretical basis for computing an optimum variation ; the second part discusses experimental results and simulation program which corroborate the theory.

본 연구에서는 도로 소음 측정시 다양한 형태로 존재하는 환경소음의 영향을 최소화하고 시간과 장소의 구애 없이 공용 중인 도로 상에서도 측정 및 평가를 가능토록 하기 위해 타이어/포장 소음 측정용 Trailer 장비를 제작 개발하였다. 기존 문헌조사를 바탕으로 도로소음의 특성을 파악하고 국외의 다양한 CPX Trailer 관련 연구사례를 살펴보았으며, 장비의 설계 및 제작 원리를 정립하였다. 이를 바탕으로 HEART CPX Trailer 관련 연구사례를 살펴보았으며, 반무향실 제작에 관한 적합성, 장비의 측정 정밀도 및 현장 적용성 등의 검증을 위해 다양한 시험을 수행하였다. HEART CPX Trailer 장비의 반무향실 제작에 대한 적합성 시험에서는 각 주파수 대역별에 따른 적합성 및 신뢰도를 확인할 수 있었으며, 도로 소음특성 평가용 장비로서 적합하다고 판단된다. 반복측정 시험에서는 각 속도별 및 마이크론폰의 위치별로 우수한 측정 정밀도를 확인할 수 있었다. 공용 중인 상태에서 수행한 도로소음 측정 결과는 2003년 중앙대학교에서 교통 개방 전에 동일구간에 대해 수행하였던 CPB 측정 결과와 유사한 경향을 보였다. 이는 견인차량의 기계소음을 비롯한 공용 중인 도로 주변의 환경소음으로부터 영향을 거의 받지 않기 때문이라 판단되며, 본 장비를 활용한다면 공용 중에도 객관적인 소음 측정이 가능함을 확인할 수 있었다.