ANNEX 1
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 off：
.1 receiving sound signals from all directions in the audio band 70Hz-820 Hz;
.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 loudspeaker.
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.
* This may be accomplished by means of at least four microphones and separate reception channels.
