4 Audible alarms and calls
Clasification Society 2023 - Version 9.38
Statutory Documents - IMO Publications and Documents - International Codes - Alarms and Indicators - Code on Alarms and Indicators, 1995 Resolution A.830(19) - 4 Audible alarms and calls

4 Audible alarms and calls

  4.1 Required alarms should be clearly audible and distinguishable in all parts of the spaces where they are called for. Where a distinct difference between the various audible alarms and calls cannot be determined satisfactorily, as in machinery spaces with high ambient noise levels, it is permitted, with the exception of the fire-extinguishing medium alarm, to install common audible alarm and call devices supplemented by visual alarms and indicators identifying the meaning of the audible alarm or call.

  4.2 The fire-extinguishing medium alarm should have a characteristic which can be easily distinguished from any other audible alarm or call installed in the space(s) concerned, and should not be combined with any other audible alarm or call.

  4.3 Audible alarms and calls should have characteristics in accordance with section 6.

  4.4 In large spaces, more than one audible alarm or call device should be installed, in order to avoid shock to persons close to the source of sound and to ensure a uniform sound level over all the space as far as practicable.

  4.5 Facilities for adjusting the frequency of audible alarms within the prescribed limits may be provided to optimize their performance in the ambient conditions. The adjustment devices should be sealed, to the satisfaction of the Administration, after setting has been completed.

  4.6 Arrangements should not be provided to adjust the sound pressure level of required audible alarms.

  4.7 Administrations may accept electronically generated sound signals provided all applicable requirements herein are complied with.

  4.8 Administrations may accept the use of a public address system for the general emergency alarm and the fire alarm provided that:

  • .1 all requirements for those alarms in chapters II and III of the 1974 SOLAS Convention, as amended, are met;

  • .2 all the relevant requirements for required alarms in this Code are met;

  • .3 the system automatically overrides any other input system when an emergency alarm is required and the system automatically overrides any volume controls provided to give the required output for the emergency mode when an emergency alarm is required;

  • .4 the system is arranged to prevent feedback or other interference; and

  • .5 the system is arranged to minimize the effect of a single failure, e.g. by the use of multiple amplifiers with segregated cable routes to public rooms, alleyways, stairways and control stations; use of more than one device for generating electronic sound signals; and use of electrical protection for individual loudspeakers against short circuits.

  4.9 The general emergency alarm, fire alarm (if not incorporated in the general emergency alarm system), fire-extinguishing medium alarm, and machinery alarm should be so arranged that the failure of the power supply or the signal-generating and amplifying equipment (if any) to one will not affect the performance of the others.

  4.10 The general emergency alarm should be audible in the spaces specified by SOLAS regulation III/50 with all doors and accesses closed.

  4.11 In general, audible alarm sound pressure levels at the sleeping positions in the cabins and one metre from the source should be at least 75 dB(A) and at least 10 dB(A) above ambient noise levels existing during normal equipment operation with the ship under way in moderate weather. The sound pressure level should be in the 1/3 - octave band about the fundamental frequency. In no case should audible alarm levels in a space exceed 120 dB(A).

  4.12 With the exception of bells, audible alarms should have a signal frequency between 200 Hz and 2,500 Hz.


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