Assignemnt 3 Sound
Assignemnt 3 – Sound
Construction Technology 5 – 200471
Damir Kukic 17038124
Q1. List and explain three ways that noise can be reduced at the source.
Noise can be reduced at the source by placing noise in sound proof enclosure. A special enclosure does not need to be constructed for the noise source. Structure-borne noise can be eliminated by flexible connections to the services and placing machinery on resilient supports.
Q2. Explain how noise attenuation differs for a point source and a line source.
For a point source, noise intensity is reduced by the square of the distance. The noise level is attenuated 6 dB for each doubling of the distance. As noise fans out from a point source, it covers a larger area. If a sound wave is double the distance from a point source, it will cover 4 times the area. The sound intensity at 2d will be a quarter the intensity at d.
For a line source, the noise level is inversely proportional to the distance. The noise level decreases by 3 dB at twice the distance. Peak-hour traffic is regarded as a line source. The sounds of individual cars are aggregated to form a continuous ribbon of sound. As sound spreads out from a line source, the area that it covers only increases at the same rate as the distance. Hence, a sound wave at 2d will cover an area 2 times as large as the area at d.
Q3. How do wind direction and temperature affect sound transmission?
WIND
Sound transmission can either be improved or reduced by the wind. The effect of wind depends on the direction downwind sound is refracted back towards the ground and upwind sound is diffused up and away from the ground. You can hear more clearly downwind than upwind.
TEMPERATURE
The time of day also determines the distribution of the sound.
The velocity of sound depends on the air temperature. During the day, air, near ground level, heats up when it contacts sunlit surfaces. Sound travels faster at ground level than higher up. Day time
Construction Technology 5 – 200471
Damir Kukic 17038124
Q1. List and explain three ways that noise can be reduced at the source.
Noise can be reduced at the source by placing noise in sound proof enclosure. A special enclosure does not need to be constructed for the noise source. Structure-borne noise can be eliminated by flexible connections to the services and placing machinery on resilient supports.
Q2. Explain how noise attenuation differs for a point source and a line source.
For a point source, noise intensity is reduced by the square of the distance. The noise level is attenuated 6 dB for each doubling of the distance. As noise fans out from a point source, it covers a larger area. If a sound wave is double the distance from a point source, it will cover 4 times the area. The sound intensity at 2d will be a quarter the intensity at d.
For a line source, the noise level is inversely proportional to the distance. The noise level decreases by 3 dB at twice the distance. Peak-hour traffic is regarded as a line source. The sounds of individual cars are aggregated to form a continuous ribbon of sound. As sound spreads out from a line source, the area that it covers only increases at the same rate as the distance. Hence, a sound wave at 2d will cover an area 2 times as large as the area at d.
Q3. How do wind direction and temperature affect sound transmission?
WIND
Sound transmission can either be improved or reduced by the wind. The effect of wind depends on the direction downwind sound is refracted back towards the ground and upwind sound is diffused up and away from the ground. You can hear more clearly downwind than upwind.
TEMPERATURE
The time of day also determines the distribution of the sound.
The velocity of sound depends on the air temperature. During the day, air, near ground level, heats up when it contacts sunlit surfaces. Sound travels faster at ground level than higher up. Day time