Internet protocol based audio alert system

TECHNICAL FIELD

0001The present invention relates to audio alert, site security management systems and, in particular, to an internet protocol based audio alert system utilizing hardware and software that can operate on local area networks ("LAN"), wide area networks ("WAN") or over the "cloud" to provide alert messages or notifications across single or multiple sites for which security is sought.

BACKGROUND OF THE INVENTION

0002Internet protocol based audio alert systems having a client-server computer architecture are known. Such systems may store alert messages centrally and transmit them across a network for broadcasting. However, the message broadcast response time may be slow, and there may be interference or queuing with other messages shared across the network. This results in either a delayed alert message broadcast or possibly an unintelligible alert message broadcast due to corruption of the digital signal if it is unable to be accurately converted back to analogue for broadcast. This situation is compounded when there are multiple message broadcast points or nodes, such as speakers in a multipole speaker system, as the alert message broadcast is unlikely to be synchronised causing additional intelligibility problems. Other factors, such as the distance between message broadcast points in a multipole speaker system, the ambient temperature variance between multiple message broadcast points and the ambient noise at each message broadcast point can all have an adverse effect on the reliability of the system to successfully deliver the alert message to its intended recipient(s).

0003<patcit id="pcit0001" dnum="US2005231349A1"><text>US Patent Application Publication 2005/231349 A1</text></patcit> (BHAT) discloses an evacuation system, which provides enhanced operational control to an operator. In an embodiment, each voice point module capable of playing evacuation messages is implemented as an addressable unit, and an operator can cause different messages to be played on different voice point modules using a central station. Protocols such as H.323 may be supported on both voice point modules and the central station such that control data can be sent from the central station to the voice point modules. The control data can be used as a basis to provide features such as changing the volume level, storing messages locally in the voice point modules, or specifying specific stored message to be played.

0004<patcit id="pcit0002" dnum="WO2006034246A2A"><text>PCT Application Publication WO 2006/034246 A2 (REYES ET AL</text></patcit>) discloses a rapid alert initiation, management and archival system. The system comprises computer-enabled and network-linked apparatus, software, and methods enabling rapid dissemination from a central station or decentralized location of alerts of the occurrence of threatening or dangerous events. The system permits monitoring and controlling activity of occupants during the event, archiving event data, including audio, or/and video recordings until the situation returns to normal and an all clear signal is given. The system may include a wide range of sensor systems that are strategically placed throughout the site, complex or facility, including: network IP cameras; fire or smoke detectors; sonic detectors that can be selected for or tuned to unique event signatures; rapid pressure fluctuation sensors; thermal detectors (temperature); and the like.

SUMMARY OF THE INVENTION

0005It is an object of the present invention to provide an internet protocol based audio alert system which stores alert messages on programmable devices located across a site under security management and broadcasts them in response to a very short and simple input, either instantaneously or in a time delayed and synchronized manner. In this specification and claims, the words "across a site", "across the site" and "site" are intended to include in their meaning "along a perimeter of a site and/or within a site".

0006According to the invention, there is provided an internet protocol based audio alert system for managing security across a site, comprising a network of a central server computer and one or more client computer communicating across the internet with a plurality of programmable edge devices and which control the operation of audiovisual input means and audiovisual output means located across the site, the programmable edge devices being programmed with software to enable them to store alert messages and send the alert messages to the audiovisual output means where the alert messages are broadcast in response to triggers received by the audiovisual input means, the audiovisual output means comprising a loudspeaker connected to each programmable edge device. The system further includes means for monitoring the ambient temperature at each loudspeaker and automatically adjusting the broadcast of the alert messages from one or more of the loudspeakers to compensate for the variation in the speed of sound at different temperatures and so as to synchronize the broadcast of the alert messages by each loudspeaker, and wherein the ambient temperature at each loudspeaker is received by the edge device which controls the operation of its loudspeaker, and the edge device applies the ambient temperature at its loudspeaker and the distance of the loudspeaker to a nominated central reference point, to an algorithm stored on the edge device which calculates a time delay that is used to automatically adjust the broadcast timing and synchronization of the alert messages. The system further includes means for monitoring the ambient noise at each loudspeaker and automatically adjusting the volume of the alert messages from one or more of the loudspeakers to compensate for the ambient noise. The means for monitoring the ambient temperature at each loudspeaker comprises a temperature sensor located on or adjacent to the loudspeaker.

0007The audiovisual output means may also include a visual information screen or a siren.

0008Preferably, the audiovisual input means is selected from the group consisting of a microphone, a motion sensor and a camera.

0009The alert messages are preferably audio or audiovisual alert messages which are uploaded onto the client computer and then distributed via the central server computer to the edge devices where the alert messages are stored and are ready to be sent to the audiovisual output means in response to triggers. It is preferred that the system includes means for assessing the positional relationship of the loudspeakers to a nominated central reference point and automatically synchronizing the broadcast of the alert messages by each loudspeaker, thereby avoiding or minimising any out of phase audio interference across the loudspeakers.

0010It is also preferred that the positional relationship of the loudspeakers is input on the client computer and is stored on the central server computer.

0011It is also preferred that the edge device notifies the central server computer of the ambient temperature at its loudspeaker. The central server computer applies the ambient temperature at the same loudspeaker to an algorithm stored on the central server computer which calculates a volume adjustment that is used to automatically adjust the broadcast volume of the alert messages.

0012The means for monitoring the ambient noise at each loudspeaker preferably comprises a dedicated microphone mounted on the loudspeaker.

0013It is preferred that the ambient noise at each loudspeaker is received by the edge device which controls the operation of the loudspeaker, and the edge device applies the ambient noise at the loudspeaker to an algorithm stored on the edge device which calculates a volume adjustment so as to automatically adjust the volume of the alert messages.

0014Preferably, the system includes means for self testing each loudspeaker, comprising a contact microphone located inside or close to each loudspeaker, and means for initiating and detecting a test audio transmission from each loudspeaker to assess an operational status of the loudspeaker. The operational status to be assessed is preferably either a working status or a not working status.

0015It is preferred that the test audio transmission is a dual tone multi-frequency (DTMF) signal which is stored by the edge device which controls the operation of the loudspeaker to be self tested.

0016Preferably, initiation of the signal from the loudspeaker starts with a self test instruction being sent from the client computer to the central server computer which then randomly selects the edge device, and the selected edge device generates and sends the signal to the loudspeaker for broadcast. The edge device, using the contact microphone, monitors feedback when the signal is broadcast. If a not working status of the loudspeaker is assessed, an alarm is generated and logged on the central server computer to facilitate remedial action.

0017It is preferred that the system includes means for providing live surveillance across the site, comprising a video camera fitted to or close to each loudspeaker, and means for streaming a live video feed from the video camera to the client computer where it can be viewed on a user interface screen of the client computer.

0018The video camera is preferably a closed circuit television (CCTV) camera which is internet enabled.

0019Preferably, before the live video feed can be streamed from the video camera, a live surveillance instruction is sent from the client computer to the central server computer which then opens communication between the video camera and the client computer. It is preferred that the means for streaming and viewing a live video feed from the video camera provides the live video feed simultaneously with the broadcast of the alert messages by the loudspeaker.

0020It is also preferred that the means for streaming and viewing a live video feed from the video camera provides the live video feed simultaneously with the receiving of a live audio feed from the dedicated microphone mounted on the loudspeaker.

0021In this way, the system streams both a live audio feed from the dedicated microphone and a live video feed from the closed circuit television camera back to the user interface screen of the client computer.

0022Preferably, the system includes means for streaming a live audio feed from the dedicated microphone to the loudspeaker on which it is mounted or to a group of loudspeakers in the network.

0023The live audio feed is preferably streamed from the dedicated microphone, via the edge device which controls the operation of the loudspeaker, to the central server computer where it is synchronized and then streamed back to the edge device for the loudspeaker, whereupon the edge device sends the live audio feed to the loudspeaker for broadcasting.

0024Preferably, the system includes means for streaming a live audio announcement across the site, comprising a microphone connected to the client computer and activated via a user interface thereof, and means for signaling to the central server computer that the live audio announcement is to be streamed and then streaming the live audio announcement to the central server computer which synchronizes the streaming and sends the live audio announcement to one or more of the edge devices, and then sending the live audio announcement to the or each respective loudspeaker where it is broadcast.

0025Preferably, the system includes means for recording an alert message for broadcast, comprising a microphone connected to the client computer and activated via a user interface thereof, and means for recording the alert message and then sending that alert message via the central server computer to the edge devices where it is stored. The alert message is preferably time stamped at the end of its recording.

0026The alert message, as well as being broadcast in response to triggers received by the audiovisual input means, may be broadcast upon instructions received directly from the central server computer or indirectly from the client computer via the central server computer.

0027Preferably, the system includes a programming interface for allowing a third party computer system to communicate with the central server computer. The third party computer system is preferably able to send alert messages and action notifications directly to the central server computer or indirectly to the central server computer via the client computer, whereupon the central server computer sends the alert messages to the edge devices for sending to the audiovisual output means, such as a loudspeaker, a visual information screen and a siren. The action notifications are used for prompting an action to be taken, either by the audiovisual output means or by the client computer.

0028The third party computer system is also preferably able to receive notifications from the central server computer that an action has been completed, such as the broadcasting by the loudspeakers of an alert message.

0029There has been thus outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and put into practical effect, and in order that the present contribution to the art may be better appreciated.

0030There are additional features of the invention that will be described hereinafter. As such, those skilled in the art will appreciate that the conception, upon which the disclosure is based, may be readily utilized as the basis for designing other processes and systems for carrying out the objects of the present invention. It is important, therefore, that the broad outline of the invention described above be regarded as including such equivalent constructions in so far as they do not depart from the spirit and scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

0031The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the accompanying drawings, in which: <ul id="ul0001" list-style="none"><li><figref idref="f0001">Figure 1</figref> is a schematic diagram showing the components of an internet protocol based audio alert system according to a preferred embodiment of the invention,</li><li><figref idref="f0002">Figure 2</figref> is a schematic diagram showing in greater detail an edge configuration of the system shown in <figref idref="f0001">Figure 1</figref> and which includes a loudspeaker assembly, an edge device and an Ethernet switch,</li><li><figref idref="f0003">Figure 3</figref> is a schematic diagram showing the positions of three loudspeakers that may be utilized in an internet protocol based audio alert system according to a preferred embodiment of the invention, the positions being shown relative to a nominated central reference point,</li><li><figref idref="f0004">Figure 4</figref> is a flow chart showing the steps of a preferred process of the system for assessing the positional relationship of the loudspeakers to the nominated central reference point and automatically synchronizing the broadcast of the alert messages by each loudspeaker,</li><li><figref idref="f0005">Figure 5</figref> is a flow chart showing the steps of a preferred process of the system for monitoring the ambient temperature at each loudspeaker and automatically adjusting the broadcast of the alert messages from one or more of the loudspeakers to compensate for the variation in the speed of sound at different temperatures,</li><li><figref idref="f0006">Figure 6</figref> is a flow chart showing the steps of a preferred process of the system for monitoring the ambient noise at each loudspeaker and automatically adjusting the volume of the alert messages from one or more of the loudspeakers,</li><li><figref idref="f0007">Figure 7</figref> is a flow chart showing the steps of a preferred process of the system for self testing each loudspeaker,</li><li><figref idref="f0008">Figure 8</figref> is a flow chart showing the steps of a preferred process of the system for providing live surveillance across the site, with the option of simultaneously broadcasting an alert message from one or more of the loudspeakers,</li><li><figref idref="f0009">Figure 9</figref> is a flow chart showing the steps of a preferred process of the system for providing live surveillance across the site, with the option of simultaneously receiving a live audio feed from a microphone on a loudspeaker,</li><li><figref idref="f0010">Figure 10</figref> is a flow chart showing the steps of a preferred process of the system for streaming a live audio feed from a microphone back to the loudspeaker on which it is mounted or to a group of loudspeakers,</li><li><figref idref="f0011">Figure 11</figref> is a flow chart showing the steps of a preferred process of the system for streaming a live audio announcement to a loudspeaker or to a group of loudspeakers,</li><li><figref idref="f0012">Figure 12</figref> is a flow chart showing the steps of a preferred process of the system for recording an alert message, storing it and then broadcasting the alert message, and</li><li><figref idref="f0013">Figure 13</figref> is a flow chart showing the steps of a preferred process of the system for allowing a third party computer system to communicate with the central server computer of the system.</li></ul>

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

0032With reference to <figref idref="f0001">Figure 1</figref>, the internet protocol based audio alert system shown therein generally comprises a network of a central server computer 12, a central client computer 14 and a remote client computer 30 communicating across the internet (WAN) 16 with a plurality of programmable edge devices 18. The programmable edge devices 18 control the operation of audiovisual input means and audiovisual output means located across a site under security management by the system. The programmable edge devices 18 are programmed with software to enable them to store alert messages, which are preferably short alert messages, and send the alert messages to the audiovisual output means where the alert messages are broadcast in response to triggers received by the audiovisual input means. The audiovisual output means include a loudspeaker assembly 22 connected to each programmable edge device, but may also include a siren 20 or a visual information screen 24 at selected site locations. The audiovisual output means may also be an integrated emergency warning intercommunication system (EWIS) running off a private automatic branch exchange (PABX) 26. There is also the capability for the programmable edge devices 18 to send alert messages wirelessly, such as by Wi-Fi 32, to tablet computers 28, smart phones and other Wi-Fi activated devices. The central client computer 14 is, in this embodiment, a desktop computer, and the remote client computer 30 is, in this embodiment, a tablet computer, but the client computers may alternatively be a laptop computer or a smart phone. Although not shown in <figref idref="f0001">Figure 1</figref>, the audiovisual input means may be a microphone, a motion sensor or a camera.

0033Each of the four edge configurations shown in <figref idref="f0001">Figure 1</figref> include not only their respective edge device 18 and specific audiovisual output means 22, 24, 26, 28, but also their respective Ethernet switch. The edge configurations which include the speaker assembly 22 and the visual information screen 24 utilize respective Ethernet switches 34, 35 which are both connected to an edge control room Ethernet switch 36. The edge control room Ethernet switch 36 is directly connected to the edge configuration which includes the siren 20 and Wi-Fi 32. The central control room configuration shown in <figref idref="f0001">Figure 1</figref>, which includes the central server computer 12, the central client computer 14 and the remote client computer 30, also includes a central control room Ethernet switch 38 which is connected to an Ethernet switch 40 for the edge configuration which includes the EWIS/PABX system 26.

0034With reference to <figref idref="f0002">Figure 2</figref>, the edge configuration shown therein generally comprises a loudspeaker assembly 22, a programmable edge device 18 and an Ethernet switch 34. Also included in the edge configuration is an input/output interface 42 and an audio amplifier 44. The edge device 18 is ultimately connected to the central server computer 12 via internet components which include a LAN connection 46 to the Ethernet switch 34 and a small form-factor pluggable (SFP) transceiver which plugs into a SFP port 48 of the Ethernet switch 34. The programmable edge device 18, the Ethernet switch 34, the input/output interface 42 and an audio amplifier 44 are normally housed in a locked cabinet secured near the bottom of a pole on which the loudspeaker assembly 22 is mounted.

0035The edge device 18 is also connected to the loudspeaker assembly 22 in several different ways to accommodate various audiovisual input means and audiovisual output means mounted on the loudspeaker assembly 22.

0036For broadcast of an audio transmission, such as an alert message or a self test signal, from the loudspeaker 50 of the loudspeaker assembly 22, the edge device 18 is connected to the loudspeaker 50 via the audio amplifier 44.

0037The edge device 18 is also connected directly to a microphone 52, such as the dedicated microphone or the contact microphone, mounted on the loudspeaker assembly 22. The microphone 52 can be used for monitoring the ambient noise at the loudspeaker 50 for volume adjustment purposes, for receiving a live audio feed for live surveillance purposes or for streaming back to the loudspeaker 50 or to other loudspeakers, or for self testing the loudspeaker 50.

0038The edge device 18 is also connected to the input/output interface 42 which is ultimately connected to the loudspeaker assembly 22 in two ways. In one way, the input/output interface 42 is connected directly to a temperature sensor 54 mounted on the loudspeaker assembly 22. The temperature sensor 54 can be used for monitoring the ambient temperature at the loudspeaker 50 for message broadcast synchronization purposes. In another way, the input/output device 42 is connected to the loudspeaker 50 via the audio amplifier 44.

0039The edge device 18 is not connected to a CCTV camera 56 mounted on the loudspeaker assembly 22. Instead, the CCTV camera 56, when streaming a live video feed, is connected to a client computer 14, 30 for viewing the live video feed on the user interface screen of the client computer. The live video feed from the camera 56 is streamed to the client computer 14, 30 via internet components which include a LAN connection 58 to the Ethernet switch 34 and a SFP transceiver which plugs into a SFP port of the Ethernet switch 34. Before a live video feed can be streamed, the client computer 14, 30 needs to complete a "hand shake" (also referred to later as a live surveillance instruction) with the central server computer 12 by which the connection between the client computer 14, 30 and the camera 56 is initiated and authenticated. More will be said about a means for providing live surveillance across the site, which surveillance utilizes the video camera 56, later in the specification.

0040With reference to <figref idref="f0003">Figure 3</figref>, the positions of three loudspeakers 50, 62, 64 of a preferred internet protocol based audio alert system of this invention are shown relative to a nominated central reference point 66. The distance from the central reference point 66 to loudspeaker 50 is 343 metres, to loudspeaker 62 is 2 metres, and to loudspeaker 64 is 170 metres.

0041The system includes means for assessing the positional relationship of the loudspeakers 50, 62, 64 to the nominated central reference point 66 and automatically synchronizing the broadcast of the alert messages by each loudspeaker, thereby avoiding or minimising any out of phase audio interference across the loudspeakers. In this embodiment, the positional relationship of the loudspeakers is input on the client computer 14, 30 and is stored on the central server computer 12. <figref idref="f0004">Figure 4</figref> is a flow chart schematically showing the steps in the aforementioned process.

0042The system includes means for monitoring the ambient temperature at each loudspeaker 50, 62, 64 and automatically adjusting the broadcast of the alert messages from one or more of the loudspeakers to compensate for the variation in the speed of sound at different temperatures and so as to synchronize the broadcast of the alert messages by each loudspeaker. In this embodiment, the means for monitoring the ambient temperature at each loudspeaker is a temperature sensor 54 mounted on each loudspeaker. The ambient temperature at each loudspeaker 50, 62, 64 is received by the respective edge device 18 which controls the operation of its loudspeaker, and the edge device notifies the central server computer 12 of the ambient temperature. Each edge device 18 applies the ambient temperature at its loudspeaker and the distance of the loudspeaker to the nominated central reference point 66, to an algorithm stored on the edge device 18 which calculates a time delay that is used to automatically adjust the broadcast timing and synchronization of the alert messages. The central server computer 12 applies the ambient temperature at the same loudspeaker to an algorithm (which provides a matrix of temperature versus resistance) stored on the central server computer 12 which calculates a volume adjustment that is used to automatically adjust the broadcast volume of the alert messages. As a result, the broadcast timing and the broadcast volume of the alert messages from each of the loudspeakers is such as to provide a synchronized and intelligible alert message across the site. <figref idref="f0005">Figure 5</figref> is a flow chart schematically showing the steps in the aforementioned process.

0043The following description illustrates in even greater detail how the system can assess the positional relationship of the loudspeakers 50, 62, 64 to the nominated central reference point 66 and use the ambient temperature at each loudspeaker to calculate a time delay and to calculate a volume adjustment so as to automatically adjust the broadcast volume of the alert messages and synchronize the broadcast timing of the alert messages by each loudspeaker. Note that as air temperature increases, the speed of sound (normally 343.2 m/sec in dry air at 20°C) also increases, and so any pre-set time delay determined for average temperature will have to be decreased for a higher temperature or increased for a lower temperature.

0044An operator of a client computer 14, 30 uses the user interface thereof to select a desired alert message to be broadcast in a specified zone (defined by selected loudspeakers 50, 62, 64) of the site and at a specified time. The client computer 14, 30 sends the alert message and an instruction on where and when the alert message is to be broadcast to the central server computer 12 via the IP network. The central server computer 12 receives the alert message and the instruction and calculates a suitable initial time delay to add to the specified time for the purpose of allowing the alert message and the instruction to reach the edge devices which control the operation of the loudspeakers 50, 62, 64 in sufficient time for each of them to respond in a correct sequence. The central server computer 12 sends the alert message and the instruction across the IP network to all the edge devices, but only those edge devices which control the operation of the loudspeakers 50, 62, 64 react to the alert message and the instructions. Each of those edge devices react by queuing the alert message for broadcast and then adding a suitable further time delay to the initial time delay added to the specified time by the central server computer 12. The further time delay added by each edge device is calculated by an algorithm stored on the edge device which uses the preprogrammed distance of the edge device from the central reference point 66 and uses the ambient temperature at the loudspeaker controlled by the edge device to calculate the further time delay. The addition of these time delays ensures that the broadcast of the alert message from each loudspeaker 50, 62, 64 is synchronized and intelligible. In the positional relationship of the loudspeakers 50, 62, 64 to the nominated central reference point 66 shown in <figref idref="f0003">Figure 3</figref>, the time delay to broadcast the alert message from loudspeaker 50 is the specified time plus 1 second, from the loudspeaker 62 is the specified time plus 0 seconds, and from the loudspeaker 64 is the specified time plus 0.5 second.

0045The system includes means for monitoring the ambient noise at each loudspeaker 50, 62, 64 and automatically adjusting the volume of the alert messages from one or more of the loudspeakers to compensate for the ambient noise. In this embodiment, the means for monitoring the ambient noise at each loudspeaker is a dedicated microphone 52 mounted on each loudspeaker. The ambient noise at each loudspeaker 50, 62, 64 is received by the respective edge device 18 which controls the operation of the loudspeaker, and the edge device applies the ambient noise at the loudspeaker to an algorithm stored on the edge device 18 which calculates a volume adjustment so as to automatically adjust the volume of the alert messages. <figref idref="f0006">Figure 6</figref> is a flow chart schematically showing the steps in the aforementioned process.

0046The system includes means for self testing each loudspeaker 50, 62, 64 comprising a contact microphone 52 located inside or close to each loudspeaker, and means for initiating and detecting a test audio transmission from each loudspeaker to assess an operational status of the loudspeaker. The operational status to be assessed is either a working status (YES) or a not working status (NO). In this embodiment, the test audio transmission is a dual tone multi-frequency (DTMF) signal which is stored by the edge device 18 which controls the operation of the loudspeaker 50 to be self tested. Initiation of the signal from the loudspeaker 50 starts with a self test instruction being sent from the client computer 14, 30 to the central server computer 12 which then randomly selects an edge device, and the selected edge device 18 generates and sends the signal to the loudspeaker 50 for broadcast. The edge device 18, via the contact microphone 52, monitors feedback (eg. volume level) when the signal is broadcast. If a not working status of the loudspeaker 50 is assessed, an alarm is generated and logged on the central server computer 12 to facilitate remedial action. <figref idref="f0007">Figure 7</figref> is a flow chart schematically showing the steps in the aforementioned process.

0047The system includes means for providing live surveillance across the site, comprising a video camera 56 fitted to or close to each loudspeaker 50, 62, 64, and means for streaming a live video feed from the video camera 56 to the client computer 14, 30 where it can be viewed on a user interface screen of the client computer. In this embodiment, the video camera 56 is a closed circuit television camera (CCTV) which is internet enabled. Before the live video feed can be streamed from the video camera 56, a live surveillance instruction is sent from the client computer 14, 30 to the central server computer 12 which then opens communication between the video camera 56 and the client computer. If required, the means for streaming and viewing a live video feed from the video camera 56 provides the live video feed simultaneously with the broadcast of the alert messages by the loudspeaker 50. <figref idref="f0008">Figure 8</figref> is a flow chart schematically showing the steps in the aforementioned process.

0048Also, if required, the aforementioned means for streaming and viewing a live video feed from the video camera 56 provides the live video feed simultaneously with the receiving of a live audio feed from the dedicated microphone 52 mounted on the loudspeaker 50. <figref idref="f0009">Figure 9</figref> is a flow chart schematically showing the steps in the aforementioned process.

0049In this way, the system streams both a live audio feed from the dedicated microphone 52 and a live video feed from the closed circuit television camera 56 back to the user interface screen of the client computer 14, 30. Such live visual and audio monitoring allows the subsequent alert messages to be tailored or specifically responsive to the events unfolding on the user interface screen and speaker of the client computer 14, 30.

0050The system includes means for streaming a live audio feed from the dedicated microphone 52 to the loudspeaker 50 on which it is mounted or to a group of loudspeakers in the network. In this embodiment, the live audio feed is streamed from the dedicated microphone 52, via the edge device 18 which controls the operation of the loudspeaker 50, to the central server computer 12 where it is synchronized and then streamed back to the edge device 18 for the loudspeaker. The edge device sends the live audio feed to the loudspeaker where it is broadcast. <figref idref="f0010">Figure 10</figref> is a flow chart schematically showing the steps in the aforementioned process.

0051The system includes means for streaming a live audio announcement to one or more loudspeakers across the site, comprising a microphone 52 connected to the client computer 14, 30 and activated via a user interface thereof, and means for signaling to the central server computer 12 that the live audio announcement is to be streamed and then streaming the live audio announcement to the central server computer 12. The central server computer 12 synchronizes the streaming and sends the live audio announcement to one or more of the edge devices 18, and the live audio announcement is then sent to the or each respective loudspeaker 50, 62, 64 where it is broadcast. <figref idref="f0011">Figure 11</figref> is a flow chart schematically showing the steps in the aforementioned process.

0052The system includes means for recording an alert message for broadcast, comprising a microphone 52 connected to the client computer 14, 30 and activated via a user interface thereof, and means for recording the alert message and then sending that alert message via the central server computer 12 to the edge devices 18 where it is stored. In this embodiment, the alert message is time stamped at the end of its recording. The alert message, as well as being broadcast in response to triggers received by the audiovisual input means, such as the microphone 52, a motion sensor or a camera, may be broadcast upon instructions received directly from the central server computer 12 or indirectly from the client computer 14, 30 via the central server computer 12. <figref idref="f0012">Figure 12</figref> is a flow chart schematically showing the steps in the aforementioned process.

0053The system includes a programming interface for allowing a third party computer system to communicate with the central server computer 12. In this embodiment, the third party computer system is able to send alert messages and action notifications directly to the central server computer 12 or indirectly to the central server computer via the client computer 14, 30, whereupon the central server computer sends the alert message to the edge devices for sending to the loudspeakers and/or other audiovisual output means. The action notifications are used for prompting an action to be taken, either by the audiovisual output means or by the client computer. The third party computer system is also able to receive notifications from the central server computer 12 that an action has been completed, such as the loudspeakers broadcasting, via the edge devices 18, an alert message. <figref idref="f0013">Figure 13</figref> is a flow chart schematically showing the steps in the aforementioned process.

0054The system of the present invention requires less bandwidth than those internet protocol based audio alert systems which store long alert messages centrally and transmit them across a network for broadcasting. The shorter alert messages which are transmitted in the system of the present invention (because they take the electronic form of smaller data packets) minimize the risk of degradation and errors in the transmissions, are less vulnerable to attack by security threats, and increase the capacity to synchronize the broadcast of the messages, making the system more reliable than known server driven systems where alert messages are stored and transmitted from a central server computer.

0055The system of the present invention is multifunctional, as it can send audio and audiovisual alert messages, and can respond in these ways to different trigger inputs, such as intruder detection and temperature increase, without the involvement of a central server computer.

0056Synchronous broadcast of each alert message from the loudspeakers is an important feature of the present invention. The location of all the loudspeakers in the network is known by a global positioning system (GPS) and the temperature at each loudspeaker is also monitored. With this information, the timing and volume of the broadcast of the alert message from each speaker can be adjusted based on the speed of sound at the relevant temperature, thereby ensuring that the alert messages are synchronized to maximize broadcast deliverability and intelligibility, and to minimize alert message interference.

0057Live surveillance using a video camera fitted to a loudspeaker simultaneously with an audio transmission from the loudspeaker is another important feature of the present invention. This is achieved using known video transmission software which cooperates with an audio data stream over the same internet protocol network.

0058Another important feature of the present invention is that its client-server computer architecture is built on the Microsoft Windows™. NET operating system which confers reliability and seamless integration with many existing networks and infrastructure.

0059It will be readily apparent to persons skilled in the art that various modifications may be made in details of design and construction of the embodiments of the internet protocol based audio alert system, and in the steps of using the system described above, without departing from the scope or ambit of the present invention.