고층 아파트의 도로교통소음 전파특성에 관한연구

Abstract

Quantitative evaluation for the sound source to predict the noise in the field point for the Road Traffic Noise was conducted. The traffic noise level and frequency characteristics as per types of cars for wave process until the noise reaches the field point was measured. Suggesting countermeasures against traffic noise, the result of modeling the noise level distribution of the apartment using RAYNOISE is as follows. 1. Frequency Characteristics as per type of Car (1) Frequency Characteristics while Driving Under freely flowing conditions of traffic, when you drive a bus on a public road, the traffic noise level showed a change of 6.2 dB(Z) from 83.1 dB(Z) to 89.3 dB(Z).The change of traffic noise level was 6.3 dB(Z) from 81.7 dB(Z) to 88 dB(Z) when a van was driven, and 10.8 dB(Z) from 79.5 dB(Z) to 90.3 dB(Z) when a one-ton truck was driven. Also, the change of traffic noise level was 18.6 dB(Z) from 81.3 dB(Z) to 99.9 dB(Z) when a motorcycle was running. All vehicles except for the motorcycle showed similar noise levels of 31.5, 500, 1 k and 2 kHz. The bus showed the highest noise level at 63 Hz and 125 Hz, and a van and an 11 ton truck showed the highest levels at 125 Hz. The one-ton truck was measured at 63 Hz for the highest noise level. The motorcycle was measured at 250 Hz with the highest noise level of 96.7 dB(Z) and at 500 Hz with 95.5 dB(Z), indicating the highest noise level among specific vehicles. (2) Characteristics of Frequency upon Departure The noise level when an urban bus stops to depart was 94.6 dB(Z), which is higher than that of stoppage and driving. When a bus stops, the normal cars have an influence on the noise level, and after departure, it brings out the highest noise at 250 Hz and 500 Hz, which is caused by noises from the engine and exhaust. The noise level when a normal car stops to depart was higher than that of stoppage and driving at 85.7 dB(Z). It is high at 63 Hz as it is being reduced from 250 Hz. While a normal car is stopping, higher noise is made at 31.5 Hz, which is considered to be caused by engine noise. 2. Characteristics of Noise Level Attenuation as per Frequency of Apartment Space The noise level outside of a window and in the center of a living room was measured to be lower on the 1st floor. Noise levels were similar on the 5th and 8th floors and lower on the 11th floor and on an 8th floor balcony. Comparing the difference of measured values on the balcony and in the center of the living room had a minus value for an applicable value of 62%, which means the balcony is the path where the sound is being passed. Because the center of the living room is a closed space, it is considered that the sound became higher by reflection and diffraction of sound in the living room. Change of frequency Attenuation as per space in the 1st, 5th and 8th floors showed the attenuated condition becoming greater as frequency rose by 1 kHz, and it became greater on the higher floors at 31.5 Hz and 63 Hz. On the 11th floor, 63 Hz appeared to have a higher attenuated condition, and it was attenuated similarly in general. 3. Modeling Using RAYNOISE for Noise Level and Characteristics of Frequency in Apartment Space Noise levels measured on the exterior wall of the apartment, on the balcony and in the center of a living room revealed to be higher in low frequency bandwidths in the lower floors. They decreased on the higher floors including the 7th and 8th floors, increased, then decreased again on the 9th floor. The noise level in the living room was 45.3 dB(Z), which appeared to be higher than that of the balcony(41.1 dB(Z)). It was also higher than the balcony in all frequency bandwidths. When actually measured, the noise level was rather high in the center of the living room. The balcony, which is a moving path of traffic noise, showed a low noise level. Traffic noise that went through the balcony might have come into the living room with a higher level of noise due to sound reflection and diffraction. We then compared noise levels in two cases while the window of the living room was open. The first case kept the window of balcony 2(bed room 2 directions) closed while the window of balcony 1(living room directions) remained open. The second case kept the window of balcony 1(living room directions) closed while the window of balcony 2(bed room 2 directions) remained open. The noise level in the center of the living room was 45.0 45.6 dB(Z) in the former case and 28.5 29.5 dB(Z) in the latter, thus showing the attenuated effect of 15.9 16.6 dB(Z). The attenuated effect appeared to be 16.9 17.9 dB(A) characteristics of A.