noise pollution Flashcards
why is a logarithmic scale used to measure noise pollution
the human ear is sensitive to a wide range of sound levels
what is the range frequency range of human hearing
20-20000 Hz
what are the effects of noise on non-living objects
1) acoustic fatigue= objects have a frequency where they eventually vibrate , eventually this could cause structural fractures
2) vibration damage= repetitive vibration can cause structural damage to buildings and bridges caused by the vibrations from the wheels of heavy vehicles
3) shock impacts= force of impact of a sudden loud no8ise can cause damage such as sonic booms
what are the effects of noise pollution on living organisms
1) hearing damage
2) stress-related health issues= can cause high blood pressure and heart disease
3) behavioural changes= irritability, aggression or lack of concentration
4) disturbance of breeding birds= birds which sing to establish territories or attract mates have difficulty in urban areas due to background noise, birds scared by sudden noises may leave nests allowing predators to take eggs
5) reduced feeding success= animals which use hearing to find food such as owls may not be able to do this as easily
outline methods military aircraft use to minimise noise nuisance
1) major urban areas are avoided
2) flight paths vary
3) low flying timetables can be published
4) flights may avoid sensitive ecological sites such as seabird cliff breeding colonies
5) possible to request a stop to low flying temporarily for agriculture
compare noise produced from military aircraft vs civil
1) civil air liners cruise at higher altitudes so little to no sound reaches floor
2) air ports are located closer to urban areas to reduce travel time increasing noise
3) noise nuisance at airport is affected by timing and number of flights each day
outline how airports can be designed and located to minimise noise pollution
1) location away from major population centres
2) taxi areas away from residential areas
3) engine test areas
4) acoustic insulation ie double glazing
5) noise absorption ie baffle mounds
overall control airport layout so noisy stuff is away from residential areas
outline how aircraft engines can be designed to reduce noise pollution
1) high bypass-ration engines= introduction of a second cowling and turbofan on front of the jet forcing bypass air around inner cowling smoothing flow of exhaust air reducing Noise
2) engine hush kits- fitted to low bypass ratio engines ( louder) to make them quieter
3) engine acoustic liners- used in inside the outer cowling and around the inner cowling to absorb noise
outline how aircraft bodies can be designed to reduce noise pollution
1) blended wing aircraft- engines located on top of the aircraft so body acts as a barrier reducing noise reaching the ground
2) lighter aircrafts- using composite materials decreases weight so less engine thrust is needed
outline how aircrafts can be operated to reduce noise pollution
1) take of angle- air crafts are nosier when taking off than ;landing as engines running at higher power
2) flight path planning- routes are planned to avoid densely populated areas when possible
3) night flight restrictions- airports near residential areas restrict number of night flights
how can noisier aircrafts be controlled
1) Charges for nosier aircrafts based on noise level
2) restricted flight times
3) control of supersonic flights
outline some sources and controls of railway noise
1) wheel vibration= track polishing, sound absorbing ballast
2) engine noise- sound absorbing suspension
3) braking squeal- use of composite material brakes
how is road traffic noise measured
1) LA10= noise exceeded for 10% in any set period
2) LA90= noise exceeded for 90% in any set period in quiet periods
3) TNI= traffic noise index= repraesentive measure of traffic noise using LA10 and LA90
