Audio for Surveillance Systems Tutorial

By: 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:

IP Camera Specification / RFP Guide 2017 on Aug 14, 2017
RFPs are hard. Do them 'right' and it takes a lot of knowledge and time. Do them 'wrong' and you can be (a) unwittingly locked into a specific...
Axis Network Horn Tested (C3003-E) 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...
Comments : PRO Members only. Login. or Join.

Related Reports

Sighthound Transforms Into Enterprise AI Provider on Jun 14, 2019
Sighthound is now rapidly expanding its R&D team, building an enterprise AI service. This may come as a surprise given their origins 6 years...
Embattled $400 Million China Funded Philippines Surveillance System Proceeds on Jun 13, 2019
An embattled 12,000 camera surveillance system project that will cost ~$400 million will proceed.  The project contract was awarded, had its...
Carnegie Mellon AI Startup Zensors Profile on Jun 11, 2019
Zensors is a startup formed by Carnegie Mellon graduates from a Carnegie Mellon research project, offering customized models per camera that they...
Avigilon 32MP and 12MP H4 Multisensor Cameras Tested on Jun 11, 2019
Avigilon has released their H4 Multi-Sensor line of cameras claiming "broad scene coverage and high image detail" We bought and tested the...
Directory of 30+ VSaaS / Cloud Video Surveillance Providers on Jun 07, 2019
This directory provides a list of VSaaS / cloud video surveillance providers to help you see and research what options are available. 2019 State...
OpenALPR Doubles Prices on Jun 06, 2019
There is no 'race to the bottom' in cloud / AI video surveillance. In May, Verkada increased their prices. Now, OpenALPR is doing the same with a...
"New" Arecont Fixes Failures "Without A Fight" on Jun 05, 2019
The "old" Arecont was infamous not only for its camera failures but for making their "partners" fight to get them fixed. IPVM drew the ire of...
Startup Rhombus Systems Says Twice the Features, Half the Price of Verkada on Jun 04, 2019
Closed cloud systems may be the fastest growing segment of video surveillance with Meraki and Verkada. Now another California company is joining...
China / US Trade War Impact Splits Industry on Jun 04, 2019
As the trade war continues to heat up, 170+ integrators told us "What impact will the US / PRC China conflict have on the industry?" Respondents...
Smart CODEC Usage Statistics 2019 on Jun 03, 2019
Smart codecs are now nearly a standard feature in IP cameras, but our statistics show integrator adoption has not increased at the same rate. In...

Most Recent Industry Reports

Sighthound Transforms Into Enterprise AI Provider on Jun 14, 2019
Sighthound is now rapidly expanding its R&D team, building an enterprise AI service. This may come as a surprise given their origins 6 years...
ADT Eliminating Acquired Brands, Unifying Under 'Commercial' Brand on Jun 14, 2019
ADT is eliminating the brands of the many integrators it has acquired over the past few years, including Red Hawk, Aronson Security Group (ASG),...
NSA Director Keynoting Dahua and Hikvision Sponsored Cybersecurity Conference on Jun 13, 2019
The technical director for the NSA’s Cybersecurity Threat Operations Center will be keynoting a physical security cybersecurity conference that is...
Farpointe Data Conekt Mobile Access Reader Tested on Jun 13, 2019
California based Farpointe Data has been a significant OEM supplier of conventional access readers for years to companies including DMP, RS2, DSX,...
Embattled $400 Million China Funded Philippines Surveillance System Proceeds on Jun 13, 2019
An embattled 12,000 camera surveillance system project that will cost ~$400 million will proceed.  The project contract was awarded, had its...
False Verkada 'Unrivaled' Low Light Performance Claim Removed on Jun 12, 2019
Verkada falsely claimed that it delivered 'UNRIVALED LOW LIGHT PERFORMANCE' until IPVM questioned. In fact, Verkada's low light performance is...
Manufacturer Favorability Guide 2019 on Jun 12, 2019
The 259 page PDF guide may be downloaded inside by all IPVM members. It includes our manufacturer favorability rankings and individual...
Camera Course Summer 2019 - Register Now on Jun 12, 2019
Register for the Summer 2019 Camera Course.  This is the only independent surveillance camera course, based on in-depth product and technology...
Favorite Wireless Manufacturers 2019 on Jun 12, 2019
Many wireless options exist for video surveillance but how are integrator's overall favorites? 170 integrators answered the question: What is...
Carnegie Mellon AI Startup Zensors Profile on Jun 11, 2019
Zensors is a startup formed by Carnegie Mellon graduates from a Carnegie Mellon research project, offering customized models per camera that they...

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