NAV 44/7
ANNEX 3
DRAFT RECOMMENDATION ON
PERFORMANCE STANDARDS FOR SOUND RECEPTION SYSTEMS
1 INTRODUCTION
1.1 Sound reception systems are
acoustical electronic navigational aids to enable the officer
on the watch to hear outside sound signals inside a totally
enclosed bridge in order to perform the look-out function as
required in the International Regulations for Preventing
Collisions at Sea, 1972.
1.2 Sound reception systems should,
in addition to the general requirements contained in
resolution A.694(17), comply with the following minimum
requirements.
2 FUNCTIONAL REQUIREMENTS
2.1 Sound reception systems should be
capable of:
.1 receiving sound signals
from all directions in the audio band 70Hz - 700Hz;
.2 reproducing incoming sound
signals acoustically inside the bridge;
.3 indicating the approximate
direction of incoming sound signals to determine at least
whether the sound signal being detected is forward or
abaft of the beam and from which side of the ship it is
being detected;* and
.4 suppressing unwanted
background noise and allowing reception of meaningful
sounds.
3 METHOD OF PRESENTATION
3,1 Incoming sound signals should be
reproduced inside the bridge by means of at least one louds
peaker.
3.2 The volume should be adjusted by
means of one volume control only. The volume control should
be capable of being set so that the sound pressure level of
an incoming signal only is at least 10 dB(A) above the bridge
noise level.
3.3 There should be a display which
gives a visual indication for at least 3 s of the incoming
signals and their approximate direction.
* This may be accomplished by
means of at least four microphones and separate reception
channels.
4 INSTALLATION
4.1 The microphones should be
installed in such a way that they are as far from noise
sources in the ship as is reasonably practicatible and wind
induced noise and mechanical vibrations are reasonably
reduced
4.2 The display should be installed
so that it is visible at least from the work station for
navigation and traffic surveillance/manoeuvring.
4.3 The loudspeaker(s) should be
installed so that incoming sound signals are audible at all
positions inside the bridge.
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