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A simple definition of noise is: Any unwanted sound.
Noise is measured in decibels and the scale often employed dB(A)
is weighted to the range perceived by the human ear. The decibel
system is frequently misinterpreted as it is based on a logarithmic
scale. This means that a sound level of 100dB(A) contains twice the energy of a sound
level of 97dB(A).
A rise of 10 dB in sound level corresponds roughly to a doubling of
subjective loudness. Therefore a sound of 80 dB is twice as loud as a
sound of 70 dB which is twice as loud as a sound of 60 dB.
Correspondingly, the 80 dB sound is 4 times louder than the 60 dB sound.
Distance plays an important role in the perceived sound level. Sound
levels decrease by approximately 6 dB every time the distance from the
source is doubled.
A noise level of 35–40dB outside a dwelling is acceptable and a maximum
of 45dB should be adhered to in order to prevent disturbance to
residents
Sound levels inside a property will be approximately 10dB less than
those outside, even when a window is open.
Noise not only affects hearing. It affects other parts of the body and
body systems. It is
now known that noise:
Increases blood pressure
Has negative cardiovascular effects such as changing the way the heart
beats
Increases breathing rate
Disturbs digestion
Can cause an upset stomach or ulcer
Can negatively impact a developing foetus and possibly contribute to
premature birth
Makes it difficult to sleep, even after the noise stops
Intensifies the effects of factors such as drugs, alcohol, carbon
monoxide and ageing
In fact research now suggests that noise may be causing 2000-4000 deaths annually as a result of an increase in cardiovascular disease
Example Sound Levels
| Faint: |
|
0dB |
The threshold of human hearing (roughly the sound of a mosquito flying 3
m away) |
| 15dB |
Leaves rustling / Calm breathing |
| 30dB |
A quiet room / Whisper |
|
Moderate: |
| 50db |
Moderate rainfall |
| 55dB |
Normal conversation |
| Loud: |
| 60dB |
TV sound at home / Dishwasher |
| 70dB |
Car at 10 metres / Vacuum cleaner |
| 80dB |
Busy traffic at 10 metres / Alarm clock |
|
85dB |
Hearing damage (due to long-term exposure)
|
| 90dB |
Power tools / Lawnmower |
|
Very Loud: |
| 100dB |
Pneumatic road drill at 1m / Chain saw /
Jet ski |
|
120dB |
Hearing damage (due to short-term
exposure) |
| 120dB |
Amplified music at 2m / Loud car stereo |
| Painful: |
|
130dB |
Threshold of pain
|
| 130dB |
Jet taking off (100m away) |
| 140dB |
Rifle being fired at 1 metre |
| 150dB |
Jet engine at 30 m / Rock music peak
|
| 194dB |
Theoretical limit for a sound wave at 1
atmosphere environmental pressure |
In order to prevent disturbance
to nearby residents, entertainment venues should fit one of the products
below to control sound levels from bands / DJs etc.
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