Noise Measurement
Noise level is measured in decibels (dB). The louder the noise, the higher the decibels. Decibels can be adjusted to human hearing. Noise level is thus described in decibels A (dBA). The effects of noise vary with the noise to which a person is exposed. Prolonged exposure to loud noises (75 dBA over eight hours a day for years) can lead to hearing loss. The body can also respond to lower noise levels: sleep can be disturbed by an outdoor noise of 40 dBA.
Examples of Noise Sources and Human Responses by Noise Level
0 dBA
Example of noise:
no sound is perceptible.
Human reaction:
the threshold of hearing.
10 dBA
Example of noise:
breathing.
Human reaction:
the sound is barely audible.
20 dBA
Example of noise:
whispers heard a metre away; light wind in trees.
Human reaction:
a sense of deep calmness.
30 dBA
Example of noise:
a low-voice conversation.
Human reaction:
a sense of calmness.
40 dBA
Example of noise:
library, refrigerator, a quiet street at night.
Human reaction:
a peaceful area.
50 dBA
Example of noise:
moderate rain, washing machine.
Human reaction:
the beginning of disturbance.
60 dBA
Example of noise:
normal conversation.
70 dBA
Example of noise:
busy street, vacuum cleaner.
Human reaction:
disruptive when on the telephone.
80 dBA
Example of noise:
alarm clock, factory, noisy restaurant.
Human reaction:
difficult to have a conversation; a feeling of heavy noise.
90 dBA
Example of noise:
subway, lawnmower, alarm.
100 dBA
Example of noise:
drill, chainsaw, motorcycle.
110 dBA
Example of noise:
loud concert, club.
Human reaction:
bearable for a short period of time; maximum vocal effort to be heard.
120 dBA
Example of noise:
emergency vehicle siren, airplane takeoff heard from about 300 metres.
Human reaction:
beginning of pain.
130 dBA
Example of noise:
jackhammer, pneumatic tool.
Human reaction:
pain.
140 dBA
Example of noise:
airplane takeoff heard from about 50 metres.
Human reaction:
unbearable pain.
