Noise Pollution Flashcards
Noise
sound that is unwanted because it causes disturbance or damage
Sources of noise pollution
Aircraft, Road traffic, Railway, Industrial, Domestic
Effects of noise pollution on non-living objects
Acoustic fatigue, vibration damage, Shock impacts
Acoustic fatigue
Stress cracking of a material caused by repetitive vibrations induced by sound.
Effects of noise pollution on humans
Hearing damage/loss, stress, ulcers, high blood pressure, heart disease, irritability, aggression, accidents due to lack of concentration, communication problems
Effects of noise pollution on other organisms
Livestock panic, injuries, breeding failure, disturbance of birds, reduced feeding success, hearing damage and behavioural change
Controls of air traffic noise through airport design
Locate away for major population centres, Taxi areas away for residential areas, Engine test areas away from residentials areas, acoustic insulation and triple glazing for nearby buildings, restriction on house building close to the airport, acoustic barriers and baffle mounds, multiple runways for slower and quieter landings
Reverse thrusters
A method used on most aircraft to slow down after landing.
Cowling
A cowling is the removable covering of a vehicle’s engine. On airplanes, cowlings are used to reduce drag and to cool the engine
Controls of air traffic noise through aircraft design
High bypass-ratio engine, chevron nozzles, engine hush kits, engine acoustic liners, blended wing design, improved aerodynamics, liter materials
High bypass-ratio engine
Have a second cowling (second layer around the engine). Air is passed around the engine as well as through it. Bypass air smooths the flow of exhaust air and reduces noise, the higher the ratio of bypass air to engine exhaust air, the quieter the engine
Chevron nozzles
A serrated edge on the cowling that mixes exiting bypass and engine exhaust air with the surrounding air more smoothly and reduces noise
Engine hush kits
Can be retrofitted to older low bypass ratio engines to increase mixing of exiting exhaust air to reduce noise
Engine acoustic liners
liners inside the outer engine cowling to absorb noise
Blended wing design
A plane where there is no clear dividing line between the wings and the main body of the craft. The engine is located on top of and within the main body of the aircraft reducing noise. The design also reduces drag and therefore noise.
Improved airplane aerodynamics -
The addition of fairings (smooth coverings) in particular around landing gear reduces turbulence. Welded construction gives a smoother aerodynamic structure that rivets.
Aerodynamics
The study of airflow over surfaces to allow the design of surfaces that reduce wind resistance, turbulence, friction and noise generation.
Lighter airplane materials
The use of alternative lighter materials eg aluminium replacing steel and the use of composite high strength materials such carbon fibre reduce mass and the power required from the engine.
Controls of air traffic noise through pilot behaviour
Steep take-off angle, flight paths over less populated areas, changing flight paths, constant angle of descent, night flight restrictions
Constant descent angle
A method of approaching an airport where the aircraft descends at a constant angle, usually 3° reducing periods of high thrust
Steep take-off angle
this is noisier as the engines are running at higher power however the aircraft climbs rapidly to an altitude where it cannot be heard on the ground
Controls of noisier aircraft
Noise limits at some airports, higher charges for noisier aircraft, control of supersonic flights, Quota count systems
Supersonic flights
Aircraft that fly faster than the speed of sound, currently no civil aircraft in this category although some are in development, supersonic speeds are banned over most countries due to the supersonic boom (shock impact)
Quota count system
Points system for airports, aircraft noise at landing and takeoff is measured and allocated points. The total point score of an airport must not exceed their allocation. The system encourages the airport to accept many quieter takeoffs and landings rather than noisy ones
