2 Effects of noise pollution
2.1 Hearing loss
Hearing threshold ----The intensity of a sound required to just barely hear it is called the hearing threshold .
loud conversation, children’s screams, barking dogs, roosters, air-conditioners, washing
machines, kitchቤተ መጻሕፍቲ ባይዱn appliances .
People are more annoyed by noise in the evening and at night than at any other time.
1 sources of noise pollution
1.3 Traffic noise Traffic noises are generated by a vehicle’s power
unit, such as a jet’s engine or a truck’s motor, and from the contact between the tires or wheels and the road or rails. The greatest amount of aircraft noise is produced upon landing and takeoff because more power is used at these times.
A shift in the hearing threshold that is less severe than an acoustic trauma, but severe enough to produce a stress that impairs hearing.
2 Effects of noise pollution
2.1 Hearing loss
Noise causes discomfort at levels of 100 to 120 dB or higher, and levels of 130 to 140 dB cause pain.
Hearing loss may occur from sustained exposure at levels lower than those that cause discomfort and pain, usually about 75 to 90 dB.
1 sources of noise pollution
1.3 Traffic noise Near the airport, noise levels between 85 and 95
dB were recorded with an increase of 20-25 dB during landing and takeoff. Near railway tracks, ambient noise level increases up to 10-20 dB during train movement.
Chapter 5 Noise pollution
1 sources of noise pollution
Noise can be either natural such as wind, thunder and movement of water or man made. If all symbols of civilization---from jet planes, vehicles, railway engines to factories generators, construction, machinery, television and radio sets and public address systems have something in common--- it is the noise.
1 sources of noise pollution
1.2 Domestic noise A residential community abounds with its own
sources of noise. Loud radio and television, amplified rock music,
2.1 Hearing loss (two types )
Acoustic trauma 听觉创伤, is the result of severe damage to the interior structure of the ear caused by a blast or explosion or some other sudden, intense noise.
1 sources of noise pollution
1.1 Industrial noise Stamping metal into auto fenders, punching
holes into metal plates, riveting plates together, and crushing different materials all produce impact noise; Grinding and drilling metal produce continuous noise. Rapid air motion caused by jets of air, blower, and fans and vibration of equipment also cause noise.
When there is a shift in the hearing threshold such that sounds have to be louder and louder to be heard, we say that there has been a hearing loss.
2 Effects of noise pollution