If you’ve never considered having an audio component with your surveillance system that may be because analog CCTV systms require separate audio and video cables to be installed from end to end which becomes difficult and costly over long distances.  IP cameras make the implementation of audio a lot simpler because the audio and video information are sent over the same network cable eliminating the need for extra cabling.

More and more IP camera audio is becoming a common feature not only because it’s easier to process over a network cable but also because the importance of this additional surveillance medium is now being recognized.

Importance of IP Camera Audio

• Detect emergency situations and make sense of other events.
• Audio covers a 360° area – surveillance systems coverage is extended beyond the field of view.
• Audio detection can trigger email or, other alerts and automatically direct where a camera should record. 

Having audio integrated into your surveillance simply gives you more information about a situation.  Many times something is brought to our attention first by what we hear, not what we see.  Car alarms, gunshots, breaking glass, and screams will not be recognized by a surveillance camera without audio.  With 360° coverage, an event happening behind a camera can still be detected.

Audio Detection Alarm

In the same way that an IP camera can analyze video, they can intelligently analyze audio as well.  As noted above, audio can hear what the video cannot see.  Audio detection complements video motion detection very well because it reacts to events in areas that are too dark for the video motion detector to pick up on.

Audio detection alarms can be programmed so that when any sound (glass breaking, voices in a room, etc.) is detected, they can trigger an IP camera to:

• Send & record video and audio
• Send email or other alerts
• Active external devices – Alarms, floodlights
• Trigger a PTZ IP camera to automatically pan to a preset location to begin recording

Audio detection can be enabled all time, at specific times, or disabled.  It can also be configured to trigger an event if a sound level rises above, falls below, or passes a certain level of sound intensity.  Sony IP Cameras has a great video demonstration of this function here:

• Sony Advanced Audio Detection

Some of the applicable Sony IP cameras and video servers that have this feature can be found here:

• Sony SNC-CH140
• Sony SNC-RS46N
• Sony SNT-EX101

Three Audio Modes

If you’re considering audio for your appliction your intended use should be clear because it can affect which IP cameras you can select as there are three audio modes available:

1. Simplex:  Audio can be sent in one direction only.  Either from the camera only (most likely) or, from the user only.
2. Half-Duplex:  Audio can be sent and received in both directions (to/from camera and user), BUT only in one direction at a time.
3. Full-Duplex:  Audio is sent and received at the same time – similar to a telephone conversation.

For example, Axis offers a camera, the Axis 207MW that offers one-way audio with a built in mic while the Axis M1054 offers two-way audio support with a built-in mic and speaker.

Features such as noise cancellation and echo cancellation are also available that reduce background noise or eliminate feedback. 

Audio Compression & Audio Bit Rates

Audio compression and audio bit rates, just like video compression and video bit rates, are an important consideration when calculating total bandwidth and storage requirements.

Just like video, audio compression uses a codec to reduce the size for efficient transmission and storage.  Some audio codecs support CBR (constant bit rate) mode only or both CBR and VBR (variable bit rate) – these factors affect quality and file size.

Bit rate is an important audio setting because it determines the level of compression or, quality of the audio.  Generally speaking, the higher the compression level = the lower the bit rate = the lower the audio quality. 

Audio/Video Syncronization

Audio and video are two separate packet (data) streams that are sent over a network.  For audio and video to play back perfectly syncronized, the two packets must be time-stamped so that they match up. 

Best Practices For Audio Implementation

• Audio Equipment & Placement:  Select a location that will minimize interferring noise and one that’s as close to the source of the sound as possible.
• Amplify Audio Signal Early:  This minimizes noise in the signal chain.
• Acoustical Adjustments:  Adjust input gain and use features such as echo cancellation to improve audio quality.
• Codec & Bit Rate Selection:  Codec and Bit Rate choice affect audio quality.  High compression = low quality (but available bandwidth may be a deciding factor).
• Shielded Cable:  Shielded cable reduces disturbance and noise.  Avoid running cable near power cables or high-frequency switching signals.
• Legal Implications:  What are you allowed to record?  Some countries restrict the use of audio and video surveillance – be sure to check with your local authorities.

If you have any questions on how to enhance and extend your surveillance system with the use of audio, please call IP Camera Supply at 866-885-4853.