Australia adopts new warning signals

Around the world, there is a move toward a International Standard for Acoustics-Audible Emergency Evacuation Signal, also known as a "Temporal-Three, T-3 or Temporal Tone". The temporal tone is being adopted around the world as the standard evacuation tone pattern and allows for better recognition by all Australians and people from other countries.

Below is an article from a Standards Australia archive written by Peter Parsons about the changes expected to come into place from 2003.

Australia will adopt the ISO alert and evacuation signals for emergencies in buildings. Committee FP-002 Fire detection, warning, control and intercom systems has agreed to the use of ISO signals for fire detection and warning systems in new buildings. This will align Australia with a growing number of countries adopting the international signals. The change makes the existing tones, specified in AS 2220, redundant for new buildings.

ISO 7731 specifies requirements for auditory danger signals to alert building wardens to an emergency, such as a fire or bomb threat. Correctly designed signals can reliably call attention to a hazard or dangerous situation without causing fright. ISO 7731 specifies the temporal pattern and frequency range for the tones, but requires consideration of the installed environment to ensure that the signal is clearly audible and can be unambiguously discriminated from the ambient noise. This is especially useful in areas of high ambient noise, such as shopping centres and factories, but is equally useful for applications in quieter areas, such as health care buildings. This overcomes a known shortcoming in the existing Australian tones which, in some situations, were not as discernible.

ISO 8201 specifies the international signal which unequivocally means "evacuate the building immediately". In searching for an appropriate signal, it was considered that the levels of background noise and frequency patterns were so variable, particularly in industry, that no signalling device would be able to penetrate all background noises and frequency patterns. For this reason, ISO 8201 selects a unique three-pulse, "on/off" temporal sound pattern and the required sound pressure level in the signal reception areas. The ISO signals are quite different from the existing Australian signals which are slower, continuous ramped tones. For the audible evacuation signal to be recognisable, it is not necessary to specify the spectral content of the signal. The spectral content should be selected to satisfy the specific site requirements.

An additional advantage of using a standardized temporal pattern as the distinguishing characteristic is that the temporal pattern can also be applied to visual and tactile signals to aid people with disabilities. These visual and tactile signals can also be applied in areas where background noise is so intense that no audible signal is capable of penetrating the ambient noise.

The adoption of the ISO signals reduces Australia?s technical barriers to trade by allowing the use of equipment that currently complies with the ISO Standards.

In deciding to adopt the ISO signals, the Committee considered systems installed in existing buildings and the training effort that has already been made. The ISO signals will not be retrospective for existing buildings, so there is no additional cost to building owners. New building occupants will be trained using the new signals. To assist in the training effort and public recognition of the signals, FP-002 has established a new work item to amend the Standard for smoke alarms [AS 3786]to also require the use of the ISO evacuate signal.

The ISO signals are to be introduced by amending the general requirements for control and indicating equipment [AS 4428.0], revising the installation Standard for fire detection and alarm systems [AS 1670.1] and revising the Standards for emergency warning and intercom systems [AS 2220]. The amendment is expected to be effective from the beginning of 2003.

Mr Peter Parsons is Chairman of Standards Australia?s Committee FP-002 Fire detection, warning, control and intercom systems. He is also the Chairman of the ISO Committee responsible for fire detection and alarm system Standards, ISO TC21/SC3.

ISO warning tones for buildings

The temporal pattern consists of a 0.5 second "on" tone, followed by 0.5 second "off" phase, sounded for three successive "on" periods, then an "off" phase lasting for 1.5 seconds. This pattern is then repeated (see figure).

Single or multiple frequency tones are permitted. This includes two-step tones and tones that ramp from one pitch to another. The temporal pattern is the key parameter.

The temporal pattern can be supplemented by inserting a voice message in the pause period between the blocks of three tone bursts. Longer messages can be inserted during pauses in the tone pattern.

By Peter Parsons

Source: SAI Global

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