Notes to Table 3.2.3.7.:
3.2.4.20. Audibility of Alarm Systems (1) Except as permitted by Sentence 3.2.4.19.(5) and except as required by Clause 3.2.4.4.(2)(d), audible signal devices forming part of a fire alarm system shall be installed in a building so that, (a)  alarm signals are clearly audible throughout the floor area, and (b)  alert signals
are clearly audible in continuously staffed locations and, where there are no continuously staffed locations, throughout the floor area. (2) The sound pattern of an alarm signal
shall conform to the temporal pattern defined in Clause 4.2 of International Standard ISO 8201, “Acoustics — Audible Emergency Evacuation Signal”. (3) The sound patterns of alert signals
shall be significantly different from the temporal patterns of alarm signals. (4) In all normally occupied spaces, the fire alarm signal sound pressure level, (a) shall be not more than 100 dBA when measured at a distance of 3 m from the device, or (b) is permitted to be more than 100 dBA provided the sound pressure level measured 2 000 mm above floor level is not more than 100 dBA. (5) The sound pressure level in a sleeping room from a fire alarm audible signal device shall be not less than 75 dBA in a building
of residential occupancy when any intervening doors between the device and the sleeping room are closed. (6) Except as required by Sentence (5), the sound pressure level from a fire alarm audible signal device in a floor area shall be not less than 10 dBA above the ambient noise level, but with a minimum value not less than 65 dBA. (7) Fire alarm audible signal devices shall be supplemented by visual signal devices in any floor area in which, (a) the ambient noise level is more than 87 dBA, or (b) the occupants of the floor area, (i) use ear protective devices, (ii) are located within an audiometric booth, or (iii) are located within sound insulated enclosures. (8) Sentence (7) shall also apply in an assembly occupancy in which music and other sounds associated with performances could exceed 100 dBA. (9) Except as permitted by Sentence (13), an audible signal device located within a dwelling unit shall incorporate a means that enables the device to be silenced for a period of not more than 10 min, after which the device shall restore to normal operation. (10) Audible signal devices within a dwelling unit
or a suite of residential occupancy shall be connected to the fire alarm system, (a) in a manner such that a single open circuit at one device will not impair the operation of other audible signal devices on the same circuit that serve the other dwelling units or suites of residential occupancy, or (b) on separate signal circuits that are not connected to the devices in any other dwelling unit, public corridor or suites of residential occupancy. (11) In a building or part of it classified as a residential occupancy, (a) separate circuits shall be provided for audible signal devices on each floor area, and (b) audible signal devices within dwelling units or suites of residential occupancy shall be wired on separate signal circuits from those not within suites of residential occupancy or dwelling units. (12) Audible signal devices shall be installed in a service space referred to in Sentence 3.2.1.1.(9) and shall be connected to the fire alarm system. (13) Audible signal devices, within dwelling units
that are wired on separate signal circuits, need not include a means for silencing as required by Sentence (9) provided the fire alarm system includes a provision for the automatic signal silence within dwelling units, where, (a) the automatic signal silence cannot occur within the first 60 s of operation or within the zone of initiation, (b) a subsequent alarm elsewhere in the building will reactuate the silenced audible signal devices within dwelling units, (c) after a period of not more than 10 min, the silenced audible signal devices will be restored to continuous audible signal if the alarm is not acknowledged, and (d) the voice communication system referred to in Article 3.2.4.23. or 3.2.4.24. has a provision to override the automatic signal silence to allow the transmission of voice messages through silenced audible signal device circuits that serve the
dwelling units. (14) If a two stage fire alarm system has been installed with an automatic signal silence as described in Sentence (13), the system shall be designed so that any silenced audible signal devices serving dwelling units are reactuated whenever an alarm signal is required to be transmitted as part of the second stage.