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.

고속도로 이용차량의 증가와 함께 차량의 대형화와 고속화로 인해 고속도로 교통 소음레벨이 높아지고 있으며 저소음 포장노면 및 방음시설 설치 요청도 급격하게 증가하고 있다. 따라서 고속도로 교통소음으로 인한 민원예방과 함께 효율적이고 경제적인 소음저감 대책을 수립하기 위해서는 정확한 소음 예측 기술 마련이 필요하다. 본 연구에서는 시험도로에 포설된 다양한 포장노면에 대해서 CPX(Close Proximity Test) 및 Pass-by 소음 계측 방법을 혼용한 소음 계측 데이터를 이용하였고 차종별 단독 주행 시험을 실시하여 차량 및 노면별 음향파워레벨 산정식이 마련된 데이터를 이용하였다. 아울러, 상기 산정식의 정확성을 검증하기 위하여 고속도로 12개 지점에 대한 총 38회의 소음 계측한 데이터를 이용하여 해당 지점에 대한 소음 예측 모델을 구성하여 측정값과 예측값을 비교 평가하였다. 최종적으로 3차원 GUI 기능을 지원하는 도로교통 소음 예측 프로그램 KRON(Korea Road Noise)을 개발하였다. 이와 더불어 각 포장형태별 및 차종별에 따른 소음특성을 분석하였다.

Prescribed according to the occupational safety and health low noise measurement method was changed to personal sampling in the method to measure an area noise. Such method had the limit which did not evaluated characteristic of sound of occurrence and the place of origin. This study was peformed to establish an engineering remedy of the work-place noise. The subject was a vibration control process of the place of business in Pusan. A simulation program applied for an engineering improvement of the work-place noise. The results were as follows: 1. An noise occurrence level of the work-place before improvement was 88~97dB(A), We applied an improvement method to be established and were expected to 80~l19dB(A), 2. The level of the noise-distribution to appear in the place of origin of the work-place before improvement was 90~93dB(A) but, We executed the simulation after applied an engineering remedy and predicted 80~85dB(A). A result of the simulation blue part was changed mostly into the dark blue color. The results suggest that simulation program establishes an engineering remedy and is useful to the case to apply.

Traditional methods for demolition of rocks may not adequate specially for urban areas and historical places. Accordingly, an use of soundless demolition chemical agent (SCDA) increases in those areas. In this study, required expansive pressure of SCDA for initiating cracks in maritime bedrock was study. It was found that shape of hole and distance between holes reduced required expansive pressure up to 59%.

This study is carried out to propose an empirical equation which can promptly predict the aircraft noise level at a specific point (a receptor) near Jeju international airport by using the information of the flight path data. For this purpose, Analyses of multiple linear regression with the slant distances (SD) calculated from the gate analyses of the flight path data, aircraft noise certification levels with unit of EPNL(effective perceived noise level) and noise levels measured at receptors are performed by SPSS package. From these regression analyses for approach and departure of aircraft, we can propose empirical equations which is statistically significant. The noise levels predicted by these empirical equations are highly correlated the measured data.

Traffic noise is a kind of noise caused by cars, trains and aircraft. Among them, noise produced by cars is the most important factor in cities. According to the National Institute of Environmental Research(NIER)'s survey, Road traffic noise levels in Busan are the highest of all the cities in Korea. So, appropriate measures for road traffic noise reduction is required. For this purpose, the construction of a noise map in Busan will play a vital role. However, road traffic noise formulas are constructed considering regional characteristics such as each country road's environment and vehicle quality. Therefore, prior to constructing a noise map in Busan, examination processes about each formula constituent status and estimation process are required preferentially. In this research, the basic first stage is to estimate Busan's road traffic noise. First, investigate characteristics of each road traffic noise estimate and using this, a noise map is constructed for road traffic noise in Busan. Then the adaptation of a road traffic noise formula is evaluated.