Brian Karas: December 2011 Archives

Adding 1­‐way or 2­‐way audio to an iCVR or Rialto installation is a good way to increase the value and effectiveness of the security system. By installing speakers and microphones with the iCVR a remote operator can speak and/or listen to persons at a remote location. This capability can be used to better manage visitor access as a door intercom system, or can be used to communicate with and discourage unauthorized visitors from a monitored site.

The audio output of the is a 1VP‐P line­‐level (unamplified) signal. This is by far the most common audio output signal among IP cameras, and is compatible with a wide range of amplifiers or self-amplified speakers. For outdoor applications, typical amplifiers will be rated for 10­‐50Watts of output power. Power ratings and speaker type are dependent on the environment, other ambient noises in the area, and distance the audio signal needs to heard from.

The amplifier may be located near the speaker, near the camera/encoder, or in an indoor equipment room.  In many cases a self-amplified speaker is the most efficient approach. If several speakers are going to be connected to a single amplifier, it may be beneficial to research 25V or 70V audio systems, to minimize concerns of aggregate speaker impedance on the amplifier. If the amplifier or amplified speaker is going to be located more than 20' from the iCVR special care should be paid to route the audio signal wire from the iCVR to amplifier away from any sources of noise or electrical interference. Use of a properly shielded cable is also recommended.

For the audio input channel, the iCVR and Rialto devices expect a 1VP­‐P  line­‐level input. There are microphones available with direct line‐level outputs, or a microphone preamp can be used to provide the proper input signal level. Microphones will also typically offer a variety of different pickup patterns, and some also offer some background noise cancellation or other sound filtering features. Much like the audio output, selecting the proper microphone for a given scenario can be situation dependant. Factors such as background noise and distance between the microphone and the person or object the audio will be captured from will determine the best choice for the given jobsite. 

When the microphone is placed a long distance from the person speaking (such as on a rooftop or similar remote location) a more directional audio pickup pattern and higher gain microphone is generally used. Microphones placed at doorways or other confined areas will often use omnidirectional microphones. It is important that the installer test the proposed microphone in the installation environment, or a similar environment before proceeding with final specifications.  For customers using the audio-in features, it is recommended that "talkbox" style intercom stations are placed and clearly marked in the installation site.  Without advanced knowledge of microphones and sound system designs it is very difficult and time consuming to design a system that lets a remote operator listen-in on a large open outdoor environment.  

This technote is intended to describe basic audio components and connections. Many options for audio exist in the security industry, and Video IQ encourages the integrator to become familiar with the equipment before deploying in a production environment.

The iCVR Encoder and Rialto units utilize a single 3.5mm "stereo" connector for both the audio out and audio in connections. In order to access each signal individually you will need to connect a breakout cable to the iCVR. These cables are available online or from Video IQ. This cable connects to the Audio IO port on the Encoder or Rialto and provides a connection for the audio Input and Output signals.  The iCVR Encoder has a single Audio I/O connector, while the Rialto devices offer dual audio I/O's, meaning you can have 2 separate speakers and microphones, controlled independently.

The iCVR Dome Camera has the audio I/O on individual RCA jacks.  The color-coding matches the PC color code standards, green is audio out and pink is the microphone input.

Amplifier and speaker selection will often be dictated by to requirements of the environment. For door intercom type applications typical amplifier power ratings will be 5-10 Watts.  For outdoor loudspeaker cases you'll normally be in the 10-25 Watt range.  One of the most commonly used items for outdoor audio talk-down is the Valcom 1036-M self-amplified speaker.  This speaker has a built-in 15 Watt amplifier and is rated for marine environments, so it will stand up to most locations.  Be advised it uses a slightly funky -24VDC power supply, so be sure to buy the Valcom supply when you buy the speaker.  You can find them through several distributors, or online for around $100-$120 (not including power supply).  


If you are using a separate speaker/amp combo, it's important to be aware of a few common speaker ratings. The most important criteria to pay attention to for speaker selection are power ­handling, generally measured in watts; and impedance, measured in ohms. The power-­handling capabilities of a speaker relate to how much input power the speaker can handle. Higher power/wattage ratings do NOT equate to louder speakers, it is simply a measurement of the maximum power a speaker can handle without being damaged. The speakers power handling generally does not have to exactly match the amplifier, a 15W speaker could be used on a 25W amplifier, as long as the amp was not turned up to maximum output power.

Impedance, or load, must be matched to the amplifier, 8 ohms is the most common speaker impedance in these applications. Using a speaker with a higher impedance will cause the audio volume to drop and may stress the amplifier. Speaker impedances that are lower than what the amplifier can support will often cause the power ratings of the amplifier to be exceeded, which can result in distorted or clipped audio, amplifier overheating or amplifier damage. 

For audio-­input from a microphone, it is often easiest to use a microphone with an on-­board preamp, or a matched preamp, that supplies a line-­level output. Louroe and Crown both produce microphones that fit these requirements. Louroe offers several options in their "Verifact" line of microphones, while Crown models with the -LL part number designation are line-­level output mics. 

Finally, you will need to enable the Audio Out and/or Audio In features on each iCVR that is connected to a speaker or microphone. This is done through the "Camera Settings" option, by right-­clicking on the camera's icon in View. Once in the Camera Settings window, click the "Audio" icon to set the audio properties for the device. You can use the sliders to adjust the output volume and input sensitivity for the iCVR. You can also test the audio output level by clicking the "Start" button, which will play a predefined audio clip from the iCVR out through the speaker. Click "Stop" when you have adjust the amplifier gain and/or audio output volume slider accordingly. 


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This page is an archive of recent entries written by Brian Karas in December 2011.

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