Federal Signal Corporation MOD1004, Инструкция по установке и обслуживанию

Страница: 10 / 17

3-1
SECTION III
INSTALLATION
DANGER
Electrocution or severe personal
injury can occur when making
electrical connections, drilling holes,
or lifting equipment. Therefore,
installation should be performed by
experienced electricians in
accordance with national and local
electrical codes
3-1. SIREN LOCATION.
The information in this section
provides guidelines to aid the user in
the selection of an installation site
that makes the best possible use of the
siren.
WARNING
The output level of a Modulator
Series Siren is capable of causing
permanent hearing damage. To
prevent excessive exposure, carefully
plan placement of siren and post
warnings.
If the siren is being installed as
part of a Civil Defense Warning
system, ALWAYS follow Federal
Emergency Management Agency
(FEMA) recommendations.
Careful consideration of the
factors affecting the propagation of
sound from the siren and the response
of the human ear to the sound will
optimize the ability of the siren to
effectively warn the community
outdoors.
The reduction of signal intensity,
as the distance from the siren
increases and the minimum desired
signal level at the fringe of the outdoor
area to be covered are important
considerations when choosing a siren
installation site. As the distance from
the siren increases, sound level losses
accumulate. These losses are a result
of weather conditions, the terrain,
obstructions in the sound path, the
pitch of the sound and the height of
the siren.
Optimum sound propagation
conditions exist when there are no
obstructions in the sound path, the
terrain is flat, and the air is calm.
Under these conditions, each time the
distance from the siren is doubled, the
sound level decreases by
approximately 10dB. For example, the
sound level at 100 feet (30.5m) from a
MOD6024 is 121dB. At 200 feet (61m),
the level drops to 111dB; at 400 feet
(122m) the sound level drops to
101dB; etc. This is referred to as the
“loss per distance doubled”.
A loss per distance doubled of
10dB is usually experienced because
buildings and other obstructions are
frequently present in the sound path.
In addition, the atmosphere is rarely
calm, the terrain may not be flat, and
humidity conditions may vary. As a
result, a typical loss per distance
doubled in residential areas may be
10dB, and as high as 12dB in areas
having tall buildings or other factors
detrimental to sound propagation.
Ideally in a free field, the loss would
be 6dB per distance doubled.
Experience indicates an
individual with normal hearing will
probably hear a warning signal whose
intensity is at least as high as the
ambient noise level.
Experience has also shown that
the ambient outdoor noise level in
industrial districts is typically 90dB.