Audio for Surveillance Systems Tutorial

Author: John Honovich, Published on Oct 05, 2011

One topic on which we regularly receive questions is the use of audio in surveillance systems, and what products and installation standards should be used.  In this update, we'll cover the basics of using audio with IP surveillance systems including:

  • How to Select a Microphone
  • How to Select a Speaker
  • The Pros and Cons of Built in Speakers
  • VMS Integration

[UPDATE: See our newer, in-depth Audio Surveillance Guide]

Audio Basics

Before connecting any audio source to a camera, first it is key to understand what types of inputs the camera can accept, and what these terms mean. Typically, audio inputs on cameras will accept either mic or line level signal. This, simply put, refers to the amount of voltage which the source device outputs. A microphone creates a very small amount of voltage when someone speaks into it, typically in the range of ten-thousandths of a volt. A line level signal, on the other hand, is approximately one volt. So, plugging a mic into a line level input will result in extremely faint audio, if any, and plugging a line level source into a mic input will result in loud, distorted audio. Some cameras may accept either, but require it to be manually switched to the proper level, either via dip switches or the web interface. Input and output levels can normally be found on the camera's spec sheet, as is shown on this spec sheet for the Panasonic WV-SF346 (page two, right column). Typically, line level sources are preferred, as microphones require more gain to amplify, and introduce more noise into the signal.

There are several types of outputs in the audio world, as well. For our purposes, we typically only need to know two: line level (covered above) and low-impedence (4- or 8-ohm). Most cameras will output line level only, which must then be connected to a powered speaker. That is, a speaker with a built-in amplifier, which must be powered separately. Some new products, such as the Axis P8221 I/O module also have low-impedence outputs, in Axis' case, a 4-ohm speaker output. This allows a speaker to be directly connected to the I/O module, with no external amplifier or power required, which makes cabling much simpler.

Selecting Microphones

When selecting a microphone, we must consider how the microphone will be used and where it will be mounted, which determines what pickup pattern is required. Microphones may be either directional or omnidirectional, depending on what is required. If mounting a microphone in the ceiling of an interview room, for example, we most likely would want to use an omnidirectional microphone. If mounting a microphone in a wallplate near an entry door, however, we could use a directional, hemispherical microphone, since it does not need to pick up audio in all directions.

Selecting Speakers

In selecting speakers, again, first consider what the speaker will be used for. Which will determine its size and power. If it's simply to talk to a visitor at the door, a few watts from a 3" or 4" speaker will be more than sufficent. If the speaker is to be used to alert subjects in a car dealership lot afterhours that they're under surveillance, a 15-30 watt horn is more appropriate, for better throw distance and volume. Manufacturers such as Bogen and Valcom are the largest distributors of powered speakers. Sony also recently released their own powered horn for use with surveillance systems, which accepts 24VAC power and line level input. This is useful since most powered systems require DC power supplies, while 24VAC is more likely to be used for surveillance.

Built-In Audio

Many manufacturers, such as Panasonic, ACTi, and Vivotek provide models with biult-in microphones. Cameras such as the Axis M1054 and Brickcom CB-100A cube cameras take it one step further, building a speaker into the camera. Built-in audio is, undoubtedly, the simplest way to add audio to the surveillance system, as no external connections are required. However, it lacks the same flexibility and choice of equipment of other cameras. Installing a camera with built-in audio may be a good choice for a secure vestibule, since it's a small, enclosed area. Relying on these microphones in an interview setting, however, may not provide the quality of audio needed or desired. Built-in audio is not really a common feature, with very few of the big names providing cameras with this functionality.

VMS Selection

Most of the major VMS players support bi-directional audio from IP cameras. However, this support may vary from manufacturer to manufacturer, and from model to model within a given manufacturer's line. Always verify the needed audio support is there before selecting cameras. Looking at Genetec's compatibility list, for example, we can see that some models don't support audio, some support audio in, and some support full bi-directional audio.

Some systems also allow a microphone or speaker attached to one camera to be associated with other cameras. This may be handy for an interview room equipped with multiple cameras, for example, allowing the full interview to be seen/heard on each of them. Associating a speaker with multiple cameras would allow an operator to alert intruders in a perimeter, for example, no matter which of the perimeter cameras he or she was viewing at the moment.

Normally, the VMS client supports this audio by adding a push-to-talk button associated with the camera. Pushing the button activates the speaker associated with the camera, and the operator is able to speak through a PC-connected microphone. Depending on setup, the microphone attached to the camera may be left open at all times, or triggered on event. Again, this varies based on the client software, and features may vary from manufacturer to manufacturer.

 

2 reports cite this report:

Axis Network Horn Tested on Apr 18, 2017
We bought and tested the Axis network horn C3003-E, examining setup and calibration, event audio, VMS integration, and sound pressure levels...
Surveillance Camera Specification Guide on Aug 19, 2013
Anyone reviewing RFPs knows there are countless common problems, with 'good' specs seemingly few and far between: RFPs copied from more than 10...
Comments : PRO Members only. Login. or Join.

Related Reports

Avigilon Discontinuing Rialto Analytics Line on Apr 27, 2017
Avigilon is informing dealers/partners that the legacy VideoIQ Rialto products have been discontinued, recommending the newer ACC ES Analytics...
Xandem Next Gen Intrusion Tested on Apr 26, 2017
Xandem's "full coverage motion tracking technology" is unlike any intrusion technology we have seen. We bought their new system and tested it...
Eagle Eye Exec On Mountain Of Servers - VSaaS Growth Analysis on Apr 25, 2017
Eagle Eye VP of Operations, Hans Kahler, posted a picture of himself sitting on top of a shipment of new servers, as a testament to the companies...
PureTech Video Analytics Examined on Apr 21, 2017
PureTech's analytics were chosen for a US border protection system (see related post), which the company claims no other analytics vendor was able...
Axis Network Horn Tested on Apr 18, 2017
We bought and tested the Axis network horn C3003-E, examining setup and calibration, event audio, VMS integration, and sound pressure levels...
Aqueti 100MP Mantis Camera Profile on Apr 14, 2017
One of the original gigapixel camera startups, Aqueti, which we first covered in 2012, is back. This time, they have partnered with NVIDIA,...
Hanwha Lowest Cost WiseNet X Camera (XND-6010) Tested on Apr 13, 2017
IPVM bought and tested the lowest-cost WiseNet X model, the indoor 2MP fixed focal XND-6010 dome, continuing our testing of Hanwha's new WiseNet X...
Bosch B-Series Intrusion Tested on Apr 10, 2017
Bosch is one of the biggest names in intrusion but their B-Series panels, targeted at smaller site installs and available through distribution, are...
Best and Worst - ISC West 2017 Show Report on Apr 10, 2017
IPVM went to Las Vegas, examining what vendors are showcasing and what is new. Attendance was up, according to the show, and was certainly well...
VMS Vs NVR Usage Statistics on Apr 07, 2017
What is used more often? VMS software or NVR appliances? 160 integrators told us what they most commonly use and why. [premium_content] Key...

Most Recent Industry Reports

Last Day - IP Networking Course May 2017 on Apr 27, 2017
Today is the last day to register for the May IP Networking Course. This is the only networking course designed specifically for video...
Hikvision EZVIZ Amazon Scam Revealed on Apr 26, 2017
Hikvision is violating US Federal Trade Commission guidelines and Amazon rules with a "Honest" Review Program scheme that provides gift cards to...
Anixter CEO Admits Price Deflation and Non-Exclusive Integrator Sales on Apr 26, 2017
Anixter's CEO has admitted to (1) price deflation impacting IP camera sales and (2) not always being 'exclusive' with security integrators. In...
Xandem Next Gen Intrusion Tested on Apr 26, 2017
Xandem's "full coverage motion tracking technology" is unlike any intrusion technology we have seen. We bought their new system and tested it...
Tri-Ed Favorability Results on Apr 25, 2017
Tri-Ed, owned by Anixter, far outranked Anixter, the lowest ranked company in our distributor favorability series. Still, Anixter's ownership did...
Eagle Eye Exec On Mountain Of Servers - VSaaS Growth Analysis on Apr 25, 2017
Eagle Eye VP of Operations, Hans Kahler, posted a picture of himself sitting on top of a shipment of new servers, as a testament to the companies...
Chinese 'Attacking Us From Every Direction', Says US FBI on Apr 25, 2017
"Chinese eating our lunch. Attacking us from every direction" said the US FBI's Deputy Director Andrew McCabe at the ASIS 2017 CSO Summit. .@FBI...
Axis Posts Strong Q1 2017 Financial Results on Apr 24, 2017
Axis posted strong numbers for Q1 2017, after having some challenges in 2016 (Q1 2016, Q3 2016). Inventory levels and overall spending show...
Axis Lowest Cost Outdoor IR Camera M2025-LE Tested on Apr 24, 2017
Axis has lagged offering low cost IR cameras while their Asian competitors have made IR standard even in their most entry level cameras. Recently,...
IPVM First Dean's List W2017 - Thomas Atkinson, Matt Hurly and Fredrik Lundqvist on Apr 24, 2017
IPVM is happy to congratulate and celebrate our first "Dean's List", the top students in our courses. For the Winter 2017 IP Networking course...

The world's leading video surveillance information source, IPVM provides the best reporting, testing and training for 10,000+ members globally. Dedicated to independent and objective information, we uniquely refuse any and all advertisements, sponsorship and consulting from manufacturers.

About | FAQ | Contact