Download Noise slides - Cal State LA

Noise Pollution
Noise is difficult to define!
In the Environmental Noise Survey
Guidance Document most recently
issued by the EPA8 the definition of noise is
given (guidance only) as
follows:
“Any sound, that has the potential to cause
disturbance,
discomfort or psychological stress to a
subject exposed to it, or
any sound, that could cause actual
physiological harm to a
subject exposed to it, or physical damage
to any structure
exposed to it, is known as noise.”
Three Facets of Sound:
Source
Transmission
Effect
3 Major Sets of Sources for Indoor Sources
and 5 for Outdoor Sources
Indoor: apartments & houses
office & factory
disco(?), entertainment
Outdoor: transportation
construction, industrial operations
humans-shouting, boombox
miscellaneous (pets, air
conditioners, sirens, garbage can
lids, lawn mowers,
Can You Hear?
AUDIBLE RANGE
The ear can hear sounds ranging from 20Hz to
20kHz. It is most sensitive to frequencies between
500Hz and 4000Hz, which corresponds almost
exactly to the speech band. Note that this threshold
increases significantly with lower frequencies
DBA Description
0
Absolute silence.
25
Very quiet room.
35
Rural night-time setting. No wind.
55
Day-time, busy roadway 0.5 km
away.
70
85
Busy restaurant.
Very busy pub. Voice has to be
raised to be heard.
100
120
Disco or rock concert.
Uncomfortably loud. Conversation
impossible.
140
Noise causing pain in ears.
The Power of Sound or
Intensity
Naturally, P1 and P0 must have
One fan has 50 dB, while adding a second with 56 dB only increases
noise level by 1 dB above higher one, or 57 dB.
Effects of Noise Pollution
Noise has many effects on humans, including
hearing loss, non-auditory physiological effects,
sleep disruption, annoyance, communication
interference, and other effects.
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 fetus, perhaps
contributing to premature birth
Makes it difficult to sleep, even after the noise stops
Intensifies the effects of factors like drugs, alcohol,
aging and carbon monoxide
Noise controls, hearing protection
Changes in machinery, equipment;
Enclosures of sources;
Damping with absorption;
soundproofing
Sound insulation, separation,
barriers