Sirens Installation and Maintenance

GP6, GP10 and GP12 Sirens
INSTALLATION AND MAINTENANCE
1. Installation
a. Fix siren to a firm level base at a minimum height of 3m above the ground and free
of side or top obstructions.
b. For best all round sound propagation mount the unit at a height of 4.5 to 6m with
50m clear radius all round.
c. Figure 1 overleaf shows a polar plot of the sound output from the sirens in free
space.
Please note that the propagation of sound in air is affected by the following factors
which must be accounted for when calculating the coverage of the siren:
• Variations of the propagation speed in the air
• Attenuation of the sound during propagation
• Wind and turbulence of the atmosphere
• Obstacles placed in the vicinity of siren and listener.
• Ambient noise levels
d. The plot assumes ideal free-field conditions.
The following losses must be taken into account during commissioning:
• Sound attenuation loss over distance in free-field conditions without obstructions.
Distance in Metres 1 30 100 200 500 1000 2000
GP6 135 105 95 89 81 75 69
GP10 140 110 100 94 86 80 74
Audibility
dB(A)
GP12 145 115 105 99 91 85 79
• Attenuation in decibels per kilometre due to absorption of sound in air (10°C,
90%RH).
At 500 Hz frequency the attenuation is 1.6 dB(A)/kilometre
• Absorption due to fog in decibels per kilometre.
At 500 Hz frequency the attenuation is 1.0 dB(A)/kilometre
The two figures provided for sound absorption in clear air and fog are sound losses
in addition to the typical sound losses experienced over distance indicated in the
table above.