Noise Pollution Flashcards
What is noise?
Sound which is unwanted
How is sound produced?
Vibrations passing through air, liquid or solid But not a vacuum
What is the effect of noise on objects?
If noise causes an object to vibrate at its natural resonate frequency this may result in stress cracks which is an indication of acoustic fatigue
What sort of infrastructure can be structurally damaged by repetitive vibration?
Roads
Bridges
Buildings
Aircraft
What are the physiological effects of noise on organisms?
Muscle constrictions
Increased heart rate and blood pressure
Constriction of blood vessels
Stress
Irritability
Head aches
Temporary or permanent damage to hearing
What can be over stimulated or die from loud noises?
Microscopic hair cells which line the organ of corti in the cochlea of the inner ear when dead hearing loss is permanent
What ways do animals use sound?
Navigation
Finding food
Attracting mates
Avoiding predators
How does noise pollution affect animals?
Makes it difficult for them to survive by interfering with sound
What marine organisms rely upon sound?
Whales
Dolphins
What do whales and dolphins rely on sound for?
Echolocation to feed, communicate, navigate and find mates sound interferes with this
What is an example of birds being affected by noise?
Bluebirds in noisy areas have fewer chicks
How are cows affected by noise pollution?
Cows equipped with bells tend to decrease head movements to avoid generation of the sound thereby reducing the amount of pasture plants removed
How can chronic noise stress affect male animals?
Male sex hormone and causes changes in reproductive organs and glands
Increased serum corticosteroids causing 80% decline in testosterone concentration
What is chronic noise stress?
Prolonged above 100db
What actions may be intensified by loud noises? (In animals)
Flight reactions- galloping, random movements, biting/ kicking
What is frequency? (Energy)
Number of waves per second
What is the unit for frequency?
Hertz (hz)
What is the hertz range for humans?
Can detect frequencies between 20 and 20,000 sensitive between 1000-4000
What is the abbreviation for decibel?
dB
What sound does the decibel scale measure?
All sound types
What is the decibel scale?
measure of the size of the fluctuations in the air pressure caused by sound waves
What doesn’t the decibel scale measure?
Sound volume
What type of scale is the decibel scale?
Logarithmic- 10db increase doubles intensity
Why is the decibel scale logarithmic?
Because of the wide range of human hearing response
What type of sound is the DBA scale used for?
Used for human hearing so only sound available to humans (20-20,000 hz)
What does NNI stand for?
Noise number index
What does the NNI measure?
Number of flights and the noise level of aircraft over 80db
How are the results from the NNI presented?
Range of 0-70 with aircraft noise being unreasonable in level of 50-60
How much of outside noise comes from transport?
66%
What is road vehicle noise a combination of?
Engine noise
Exhaust noise
vibration of the tyres on road surface
What is a baffle mound?
barriers made of earth, wood, metal or concrete or composites may reduce noise levels by 10-15dB
What is the problem with baffle mounds?
Houses above the height of the barrier wont be protected
What are some mechanisms to reduce traffic noise?
Traffic calming
Engine enclosure
Seal exhausts joints effectively
Fans turned off when not needed
Buffer zones or barriers
Traffic flow management
Build new roads below the level of the land surface
Use porous asphalt for road surfaces
Improve housing insulation
What is the principle with traffic calming?
Slows traffic reducing tyre noise
What is the principle with engine enclosure?
enclosure absorbs noise
What is the principle with seal exhausts joints effectively?
Reduce vibration
What is the principle with fans turned off when not needed?
Reducing number of of moving parts
What is the principle with buffer zones or barriers?
absorb noise
What is the principle with traffic flow management?
Ban lorries at times or places
Control flow by sequencing traffic lights
What is the principle with building new roads below the level of the land surface?
Embankments absorb and reflect noise
What is the principle with using porous asphalt for road surfaces?
Texture helps absorb noise
20% of its volume is pore space thus water infiltration is rapid, reducing noisy spray
What is the principle with improving house insulation? (noise pollution)
Double/ triple glazing + composite wall material absorbs sound
What is railway noise a combination of?
Engine noise
Vibration of wheels on track
How can railway noise be controlled?
Timing freight and passenger movement (ban between 12am-5am)
Ballasts
Why are ballast used on railways?
Aggregates under and between the tracks absorb noise
What is domestic noise a combination of?
Appliances (TV, dishwasher)
Garden equipment
Music
How can you control domestic noise?
Insulation e.g. double insulation to absorb or reflect noise
Considerate use
How can industrial noise be reduced?
Reduce weight and height of impacting masses
Reduce speed of spinning parts
Reducing pressure and flow velocities of circulation systems
Enclosing in acoustic insulation
Using dampening materials (viscous liquid to dissipate energy)
How can workers be protected from industrial noise?
Using ear protectors
Limiting exposure to the noise
How can airport noise be reduced?
Lighter (reduce engine power)
Aerodynamic shape
Engine smaller but more efficient
Better brakes
Limit weight carried in plane
Limit flight times
Reduce air ports bear high density urban areas
