While a picture is worth a thousand words, the spoken word can be worth much more in the physical security world. Video only tells half the story, regardless of how many megapixels are captured. Audio cues separate perception from reality.
Having audio as an integrated part of a video surveillance system can be an invaluable addition. A cry for help, the sound of breaking glass, a gunshot or an explosion in the vicinity of a camera — yet outside the camera’s field of view — could escape notice without audio.
Still, integrating audio into a video surveillance system is still not widespread. And frankly, excluding new compression methods, better quality microphones and improved analytics, not much has changed since I wrote a similar article for www.secrityinfowatch.com five years ago. Nevertheless the audio technology available today is more than enough to improve surveillance intelligence. It’s all about implementation and knowing when to add audio.
When to Add Audio
Outside of legal ramifications, audio uses in video surveillance are limitless. That’s not to say that audio capabilities should be suggested as part of every RFP, but if there’s an idea for how audio can improve a system, then there’s a solution.
First and foremost, audio detection complements video motion detection to react to events outside of the camera’s field of view or in a low-light situation when a highly light sensitive camera is not used. Video recording can be initiated when audio hits a certain decibel threshold, and it can be used to turn on lights or other systems.
Visitor management or intruder communication could also be an important auditory need for the customer. Instead of investing in an entire intercom system, the surveillance system could be used to meet the needs of communicating to visitors or warding off intruders.
Additionally, audio can be integrated into the surveillance system for remote monitoring of a restricted area or in a remote helpdesk capacity at, for instance, parking garages or bus stations.
IP-based access control systems provide another medium for leveraging audio. In a perfect visitor management system, all three — video, access and audio — combine for a true integrated solution with video and audio verification.
Then of course there are non-security uses of video surveillance with audio that can open doors to new business opportunities: telemedicine, distance learning, teaching tool packages, video conferencing, concert streaming and so on. Plenty of traditional security integrators have harnessed the power of video and audio to create completely separate and successful business units.
And as with any conversation today about surveillance technology, the focus often shifts to intelligence. Audio intelligence can tell a camera to record on the sound of a voice, broken glass or a gunshot. It can enact an alarm to sound or alert a business owner to a potential situation. It can even instruct a PTZ camera to focus on a specific area of a scene and track movement. But as with all promises of intelligent analytics, expectations must be properly set and the system must be tested before deployment.
Audio Tech Tips
The first thing to understand is that integrating audio is much easier and less costly with network video as opposed to analog CCTV. Video and audio can be sent over the same cable, which reduces cabling cost and installation effort while helping to better synchronize data. Also, in an analog system, if the distance between the microphone and recording station is too long, balanced audio equipment will be needed — further increasing system cost and installation complexity.
When an IP camera or video encoder has support for audio, it typically includes a built-in microphone but rarely a speaker. This is important if you require two-way communications (more on this later). If the device does not have a built-in microphone, then often it will have a line-in jack for an external one. The built-in microphone may be appropriate for some applications, but an external microphone may provide a better solution for applications that require higher quality sound or need to place the microphone at a specific location. There are three main types of microphones: dynamic, condenser and electret.