jotron MPA 1600, Руководство пользователя и инструкция по установке

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23
User and Installation Manual
Compact MPA
5.2.3 LOUDSPEAKER SELECTION AND SOUND PRESSURE LEVEL
The calculation of sound pressure level (SPL) is also dependant of distance from the loudspeaker:
The calculation is according to the formula:
SPL =A+(10·LOG
10
(B))-(20·LOG
10
(C))
WHERE:
SPL: Sound Pressure Level figure at a specific point [dBA]
A: Loudspeaker specific data - SPL figure at 1W / 1m (according to loudspeaker data sheet) dBA]
B: Loudspeaker specific data – Output power ((tapping according to loudspeaker data sheet) [W]
C: Distance from the loudspeaker to the measurement point [m]
FOR EXAMPLE:
The mounted loudspeaker is a DNH HP15T, (108 dBA at 1W/1m. The distance to the loudspeaker is 10m and the tapping of
the loudspeaker is 4W,
The SPL in that point is calculated with A=108 B=4 and C = 10,
THUS:
SPL =108
dBA
+ 10·LOG
10
(B) - 20·LOG
10
(C) = 94
dBA
„
Please note that under no circumstances are sound pressure levels in accessable spaces
allowed to exceed 120
dBA
.
5.2.4 NUMBER OF LOUDSPEAKERS
To determine the required number, type and tapping of loudspeakers in a Compact MPA system it is necessary to make an
installation SPL requirement chart over the site/vessel. Within this chart noise figures must be known or estimated. This,
along with the environmental requirements will form the basis for the loudspeaker selection.
When this is prepared, an SPL calculation can be performed to find the requirement for loudspeaker density. The SPL formula
in section 5.2.3 can be used to establish the number and type of loudspeakers. This will also include information about
tapping and output power.
It is also vital to take duplication into consideration. Whenever the Compact MPA system handles General Alarm or the vessel
is intended for passenger transportation the system shall be fully duplicated (A & B system) using separately located central
equipment with physically separated cables and loudspeaker segregation. All spaces shall be covered from both duplication
loops.
5.2.5 CABLE ARRANGEMENT
In a Compact MPA system that handles General Alarm (PA/GA) or if the vessel is intended for passenger transportation each
loudspeaker distribution cable shall be organised as a closed loop starting and ending at the central equipment point. This
increases redundancy regarding in the event of cable problems.
5.2.6 ZONES
In most installations there is a requirement for dividing the system into different paging zones. The Compact MPA has 6 zones
available for paging separation. Each zone is individually controlled from the MPA 1601 control unit.
The zone selection is important for loudspeaker distribution and the cabling plan preparation.