GB2251327A - Emergency evacuation - Google Patents

Abstract

An audio signal source 48 feeds loudspeakers 68, 70 of a stereo pair via amplitude modulators 60, 62 which are supplied with respective modulation signals 56, 58. Loudspeaker 68 is therefore fed with an audio signal the amplitude of which repeatedly cycles through the sequence: short rise-time/long fall-time, and loudspeaker 70 is simultaneously fed with an audio signal the amplitude of which repeatedly cycles through the sequence: long rise-time/short fall-time. The effect is of stereophonic sound repeatedly moving from loudspeaker 68 to loudspeaker 70, and this is used in an arrangement for guiding personnel during evacuation from buildings etc. The stereophonic effect can be enhanced by the so-called "wide stereo" effect, employing attenuators 82 and 84 and amplifiers 78 and 80 to add a portion of the signal in each channel in antiphase to the signal in the other. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO PERSONNEL SAFETY ARRANGEMENTS The present invention relates to personnel safety arrangements and it relates especially, though not exclusively, to such arrangements for assisting the evacuation of personnel from buildings or other enclosed areas, or areas with restricted egress and access points, under emergency conditions. Typical emergency conditions include (without limitation) structural damage due to fire or other causes, terrorist activities or a threat thereof, escapes of toxic fumes, mob violence, etc.

Previous systems for warning of emergency situations have used simple arrangements of bells or sirens to provide an audible warning of an alarm condition, although more recently voice alarms, using synthesised or tape recorded messages have been suggested as a more effective means for sounding an alarm. However, with all such systems occupants unfamiliar with the evacuation routes or procedures for the building or area have no means of determining the route to the nearest exit once the alarm has been sounded.

Hence, it is desirable to provide an alarm system which automatically guides evacuees towards exits and such systems are described, for example, in GB Patent No. 1458483 and US Patent No. 4347499. However, such systems still suffer from a distinct disadvantage in that it is possible, in indicating an exit route, to actually direct personnel towards the source of a prevailing emergency as the indicated exit route may no longer be a safe route in view of, for example, the occurrence of fire or dense smoke along the route in question.

GB 2225661A describes an emergency evacuation system in which a number of hazard detectors and audio emitters are distributed about a building or area, including the evacuation routes. A central control unit is provided which stores information about the distribution of the detectors and emitters within the area. The control unit responds to a hazard signal from any detector and causes an audio signal to 'travel' from one audio emitter to another along a route leading to safety relative to the position of the detected hazard. Persons evacuating the area are, therefore, guided to safety by the shortest available route remaining safe in the prevailing emergency. However, in the system described in GB 2225661A, the audio signal is caused to 'travel' along the safe exit routes by the sequential energisation of the audio emitters along each such safe route.The audio signal is of short duration so that the apparent travel from one emitter to the next is easily detected and followed The signal sounds from one emitter, then from the next emitter, and so on, until the exit is reached whereupon the signal cycles back to sound again from the first emitter along the safe exit route. For exit routes including long corridors the sound may be caused to cycle more frequently to ensure that unacceptable delays do not occur between successive energisations of any one sound emitter along the exit route. However, there is a limit to how frequently the exit route sound emitters can be cycled before the apparent travelling effect of the sound is diminished or even lost.

Hence, circumstances can easily arise at any location within the area where, during an emergency, the sound emitter remains de-energised for unacceptably long periods of time, such that systems of the type described in GB 2225661A cannot meet the safety regulations required of fire alarms.

The present invention seeks to provide an evacuation system which itilises a 'travelling' audible signal to guide occupants along safe exit routes but which also ensures that the sound level emitted from any sounder during an emergency situation does not fall below a predetermined level for longer than a predetermined period of time, irrespective of the length of the exit route along which the sound must be cycled, thereby enabling current safety regulations to be met.

Accordingly there is provided an emergency evacuation arrangement for indicating an exit route from a structure or region during an emergency situation, the arrangement comprising processing means for receiving electrical signals from one or more sensors for indicating the existence of an emergency situation within the structure or region and for generating alarm signals for energising sound emitters arranged along at least one exit route from the building or area, wherein the sound emitters are arranged as one or more stereophonic groups and the processing means is arranged to provide alarm signals in a manner such that the sound emitters of any stereophonic group are energised contemporaneously, the amplitudes of the alarm signals afforded to first and second sound emitters of a stereophonic group repeatedly and contemporaneously varying overall in opposite senses in such manner that the alarm signal afforded to said first sound emitter has each time a comparatively short rise time and a comparatively long fall time and the alarm signal affored to said second sound emitter has a comparatively long rise time and a comparatively short fall time for causing the array to portray a moving sound source along the at least one exit route whilst maintaining an absolute level of sound emission from the sound emitters arranged along the at least one exit route.

Stereophonic groups of sound emitters along the or each exit route may be energised by the processing means as sequential groups along the or each exit route.

The sound emitters of a stereophonic group are, preferably, arranged in a common housing.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a schematic representation of a structure or region incorporating an emergency evacuation arrangement in accordance with the present invention; Figure 2 shows a schematic block diagram of a first embodiment of the central processing unit of the arrangement illustrated in Figure 1; and Figure 3 shows a schematic block diagram of a second embodiment of the central processing unit of the arrangement illustrated in Figure 1.

Referring now to Figure 1 a structure 1 comprises a peripheral gallery 2 which communicates with four main external doors or exits, 3-6, and with various internal doors 7-10 which, in turn communicate with respective internal zones 11-14 of the structure 1.

The structure includes additional zones 15-18, and further internal doors 19-29 which permit communication between various of the zones but which do not directly communicate with the peripheral gallery 2.

The zones may be rooms, offices, laboratories or may indeed have any kind of function. Each of the zones 11-18 is provided with a respective sensor device 30-37 which, in each case, may be capable of sensing the existence of one or more alarm-worthy situations. Each sensor, for example, may have the ability to detect smoke, flame, heat and vibration or any of these or other possible indications of the existence of an emergency situation. The sensor devices generate electrical signals indicative of the existence of an emergency situation (and possibly also of the type of emergency if the devices are capable of responding to a number of stimuli) and these signals are fed into a processor in the form of a central processing unit 38, which may be arranged at any convenient location either within or remote from the structure 1.

The processing unit 38 receives and correlates all the signals from the sensor devices 30-37 and also is preferably arranged to carry out regular checks on the functionality of the sensor devices. The processing unit 38 is also capable of ascertaining in which zone each detector device is located.

This may, for example, be achieved by each sensor device generating an identity code which is transmitted to the unit 38 for correlation with a look-up table held within a non-volatile memory in the unit 38 or in any other convenient manner.

Alternatively, the alarm signals themselves may be appropriately coded for recognition by the processing unit 38 to determine location. By the above means, the processing unit 38 is rendered aware of the existence of, and possibly also the nature of, an alarm-worthy situation and of the zone of the structure 1 in which such a situation has occurred.

Each zone has an alarm indicator, shown as an acoustic generator or sound emitter 39-46, although warnings other than, or in addition to, audible warnings can be given if desired, and escape route direction markings along approved routes therein, which are indicated as pathways in Figure 1.

The processing unit 38 is programmed to monitor signals received from the sensor devices so as to readily identify the occurrence of an alarm-worthy situation within the structure 1. Upon receiving such a signal, the processing unit 38 generates alarm signals which are used to energise the sound emitters along the exit routes which are deemed to remain safe with regard to the type of alarm-worthy situation detected and the location of that situation. The decision as to which exit routes remain safe can be generated from information stored in an appropriate store within the processing unit 38.

The sound emitters 39-46 are arranged as stereophonic groups, each stereophonic group consisting, preferably, of two or three sound emitters. The sound emitters may be arranged so that the acoustic generators 39-46 each make up a stereophonic group by the provision of, for example, two appropriately directed sound emitters, such as loudspeakers, in the acoustic generator housing. Alternatively, two or more individual acoustic generators 39-46 may be arranged to constitute a stereophonic group. Such stereophonic grouping of the sound emitters will be readily evident from the description given below.

As stated previously, prior evacuation systems incorporating sound emitters dispersed along exit routes have energised the sound emitters sequentially to portray the sound source moving towards the safe exit. In the present invention the sound emitters of any stereophonic group are energised contemporaneously to provide the portrayal of the sound source moving towards the safe exit and hence, in contrast to known systems, ensuring that the absolute level of sound generated by the sound emitters along the exit route is above an absolute level The stereophonic groups of sound emitters may themselves be energised sequentially or in groups to portray the moving sound source.

The effect of 'stereo' sound is utilised to portray the moving sound source, thus enabling the absolute alarm sound level to be provided throughout the exit route during the desired evacuation period. The stereo effect can be achieved in several ways, such as by the apparatus shown in either of Figures 2 or 3, in which Figures like reference numerals have been used to designate like parts of the apparatus.

Referring to Figure 2, the processing unit 38 includes signal generators 48, 50 and 52 for generating, respectively, signals 54, 56, 58. It can be seen from Figure 2 that the (repeating) electrical signals 56 provided by the signal generator 50 consists of signals having a relatively short rise time followed by a relatively long decay time whilst those provided by signal generator 52 have a relatively long rise time followed by a relatively short delay time. In a particularly simple embodiment generators 50 and 52 may be constituted by mutually synchronised sawtooth signal generators generating ramps of positive and negative slope respectively.

Amplitude modulator circuits 60, 62 are coupled to receive the signals 54, 56, 58 provided by the signal generators 48, 50, 52. The modulator circuits 60, 62 cause the audio-frequency signal 54 to be amplitude-modulated by the signals 56 and 58 respectively, to provide alarm signals 64, 66 which are fed via amplifiers 78 and 80, respectively, to left and right loudspeakers 68, 70 of one of the sound emitters, such as 39, located within the structure 1 of Figure 1. The signals 64, 66 are also fed via attenuators 82 and 84 respectively to inverting inputs of the amplifiers 80 and 78 respectively so that each of the speakers 68 and 70 is also fed with a lower-amplitude antiphase version of the signal generated for the other.

The alarm signals 64, 66 are, in effect, synthesised wide-stereo signals and it can be seen from the envelopes of the signals that, for example, when the amplitude of alarm signal 64 is large, the amplitude of alarm signal 66 is small; and vice versa. Hence, when these signals, which occur simultaneously such as between times tl and t2 as shown in Figure 2, are fed to the left and right loudspeakers 68, 70, the left hand speaker 68 will emit initially sound at a relatively high acoustic level whilst the right hand speaker will emit initially an antiphase version of this sound at a lower level. As the sound level from left hand speaker 68 diminishes that from right hand speaker 70 initially also diminishes, then it reverses phase and increases.Towards the end of this increase the sound from speaker 68 reaches zero, reverses phase and increases somewhat once again. The combined effect, therefore, is the portrayal of a sound source moving from a location to the left of speaker 68 to a location to the right of speaker 70. The portrayal of a moving sound source similar to that provided by sequential energisation of the speakers, as with known systems, can therefore be obtained but the alarm signals can be arranged such that the left and right speakers emit sound above an absolute level at least throughout the period for which the emergency situation prevails and throughout the designated safe exit routes.The evacuation arrangement described does not suffer therefore from the sound 'dead zones' which can be manifest with known systems as the speakers, operating as stereophonic groups, can each be caused to emit sound continuously throughout the duration of the emergency situation without negating the portrayal of the moving sound source.

The processor 38 may also be provided with a summation unit 72 which is coupled to receive the alarm signals 64, 66 provided by the modulator circuits 60, 62, thereby to generate a third alarm signal 74, of the form shown in Figure 2, which can be used to energise a centre speaker 76 of the sound emitter 39, thereby to enhance the overall moving sound effect provided by the sound emitter 39. Centre speaker 76 (if present) produces sound signals having amplitude peaks situated midway between the main peaks of the signals produced by the speakers 68 and 70.

Figure 3 shows a further embodiment of processing unit 38. In this embodiment the processing unit 38 comprises a stereo voice sound generator for providing a source 90 of stereo sound signals, i.e. two signals for which at any instant in time, the phase and or amplitude of one signal normally differs from that of another of the signals. Such a source of signals may easily and conveniently be provided by moving a sound source of appropriate pitch and amplitude between two stereo microphones and recording the signals produced by the microphones on any suitable medium, such as magnetic or optical tape or disk or in a solid state memory. The left hand, L, and right hand, R, channel output signals from the source 90 are fed respectively to positive input ports of amplifiers 92, 94.The processing unit 38 also includes a first feedback circuit 96 coupled between the output of amplifier 92 and a negative input port of amplifier 94, and, additionally, a second feedback circuit 98 coupled between the output of amplifier 94 and a negative input port of amplifier 92. With this arrangement a fraction of the output signal from each amplifier, that is the signal used to feed the speaker of either the right or left hand stereo channel, is fed in antiphase to the other amplifier, and thus to the other speaker, thereby enhancing the width of the sound stage. Thus a wide stereo effect again occurs, in which the speakers 68, 70 portray a sound source moving between two locations having wider spacing than the actual physical spacing between the speakers 68, 70.Such a wide stereo sound image has been found to be particularly advantageous for use in emergency evacuation systems.

It will be evident that the amplifiers 92 and 94 of Figure 3, together with those of the feedback circuits 96, 98, should be selected so that the gain around the loop 92, 94, 96, 98 is less than unity.

The present invention may be used with a wide range of standard alarm tones and may equally be used with speech.

Furthermore, the tone or pitch of the alarm signal used to energise one sound emitter of a stereophonic group may differ from the tone or pitch of the alarm signal used to energise another sound emitter of the stereophonic group.

The present invention can provide, therefore, an emergency evacuation arrangement in which the effect of moving sound can be generated to provide audible cues for directing occupants safely from a building whilst enabling the sound to be generated continuously from any sound emitter throughout the prevalence of the emergency situation.

Although the present invention has been described with respect to specific embodiments it will be realised that modifications may be effected whilst remaining within the scope of the invention.

For example, it is not essential to make provision for the wide-stereo effect; components 78-84 in Figure 2 or components 96 and 98 in Figure 3 may be omitted if desired.

Claims (4)

1. An emergency evacuation arrangement for indicating an exit route from a structure or region during an emergency situation, the arrangement comprising processing means for receiving electrical signals from one or more sensors for indicating the existence of an emergency situation within the structure or region and for generating alarm signals for energising sound emitters arranged along at least one exit route from the building or area, wherein the sound emitters are arranged as one or more stereophonic groups and the processing means is arranged to provide alarm signals in a manner such that the sound emitters of any stereophonic group are energised contemporaneously, the amplitudes of the alarm signals afforded to first and second sound emitters of a stereophonic group repeatedly and contemporaneously varying overall in opposite senses in such manner that the alarm signal afforded to said first sound emitter has each time a comparatively short rise time and a comparatively long fall time and the alarm signal affored to said second sound emitter has a comparatively long rise time and a comparatively short fall time for causing the array to portray a moving sound source along the at least one exit route whilst maintaining an absolute level of sound emission from the sound emitters arranged along the at least one exit route.

2. An arrangement as claimed in Claim 1, wherein the processing means is arranged to provide as a component of the alarm signal afforded to said first sound emitter a phase-inverted portion of at least a component of the alarm signal afforded to said second sound emitter, and to provide as a component of the alarm signal afforded to said second sound emitter a phase-inverted portion of at least a component of the alarm signal afforded to said first sound emitter.

3. An arrangement as claimed in Claim 1 or Claim 2 wherein the processing means is arranged to provide an alarm signal to a third sound emitter of the stereophonic group, this alarm signal comprising an additive combination of portions of the alarm signals afforded to said first and second sound emitters.

4. An emergency evacuation arrangement substantially as described herein with reference to Figures 1 and 2 or to Figures 1 and 3 of the drawings.