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:

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

ACRE-Acquired Open Options Access Company Profile on Dec 17, 2018
Who is the company ACRE is acquiring? In this note, we examine Open Options line for best customer fit, key features, pricing, and main...
8MP / 4K Fixed Lens Camera Shootout - Dahua, Hikvision, TVT, Uniview on Dec 17, 2018
8MP / 4K fixed lens models are now common in lower cost lines, with nearly every Chinese brand and their OEMs now offering multiple options. To...
DVR Examiner - Video Recovery from Recorder Hard Drives on Dec 13, 2018
Bypassing passwords and long download times on-site, DVR Examiner collects and organizes video evidence directly from a hard drive extracted from...
FLIR Launches Body Cameras Unified With VMS (TruWitness) on Dec 11, 2018
While FLIR is best known for their thermal cameras, now they have expanded into body cameras, launching TruWITNESS, a public safety focused body...
Startup Sunflower Labs' Autonomous Drone Security System on Dec 11, 2018
Startup Sunflower Labs is claiming a unique design on a home security system, combining autonomous drones and 'Sunflower' sensors. Imagine an...
Infinova's Xinjiang Business Examined on Dec 07, 2018
As pressure mounts for companies to stop doing business in China’s Xinjiang region amid a severe human rights crisis, IPVM has found Infinova sold...
VMS Live Monitoring Shootout - Avigilon, Dahua, Exacq, Genetec, Hikvision, Milestone, Network Optix on Dec 05, 2018
Viewing live video is the first interaction and most common task most users have with a VMS. Who does it best and worst? Who offers the most...
Fullerton Returns, Joins OpenEye on Dec 04, 2018
Eric Fullerton became one of the most famous people in the industry as the Chief Sales and Marketing Officer of Milestone as Milestone became the...
Startup Qumulex Aims For Unified Platform, Adds Infinias Access Founder on Nov 29, 2018
The startup founded by former Exacq executives, Qumulex has hired Wayne Jared, founder of access control manufacturer Infinias and most recently a...
Vintra "AI-Powered" Video Analytics Startup Profile on Nov 27, 2018
Vintra is a Silicon Valley startup focused on AI-based video analytics. They had booths at IACP and ISC West demonstrating their hosted or...

Most Recent Industry Reports

Dahua USA Sales Team Cuts - 'Strategic Right Sizing' on Dec 18, 2018
Dahua USA finishes a tumultuous year in which it acquired the Flir SMB business, was subject to the US government ban, terminated and restructured...
This Brooklyn Storefont Sells Millions In Uniview And Hikvision on Dec 18, 2018
Looking at their Brooklyn headquarters for this "CCTV Manufacturer", it is not much: Inside, it is not better: However, this company is one...
ACRE-Acquired Open Options Access Company Profile on Dec 17, 2018
Who is the company ACRE is acquiring? In this note, we examine Open Options line for best customer fit, key features, pricing, and main...
Open Options Acquired By ACRE on Dec 17, 2018
ACRE is doing deals again. A year after they sold Mercury, they are buying another access control company - Open Options. In this note, we...
8MP / 4K Fixed Lens Camera Shootout - Dahua, Hikvision, TVT, Uniview on Dec 17, 2018
8MP / 4K fixed lens models are now common in lower cost lines, with nearly every Chinese brand and their OEMs now offering multiple options. To...
Network Cable Shootout - Belden, Commscope, Hikvision, Honeywell, NavePoint CCA, Windy City Wire on Dec 17, 2018
Every IP camera install needs UTP cabling. But how much of a difference is there between dirt cheap generic cables found online and the bigger,...
Hikvision Government Parent Holds Communist Party Congress on Dec 17, 2018
The Communist Party committee of Hikvision’s government parent, CETHIK, held a Party Congress earlier this month where senior executives, including...
Imperial Capital Security Investor Conference 2018 Review - ADT, Resideo, Alarm.com, Arlo, Eagle Eye, ACRE, More on Dec 14, 2018
Imperial Capital Security Investor Conference is an event matching industry executives with financiers that frequently leads to future funding...
Cisco Meraki New Cameras and AI Analytics on Dec 14, 2018
Meraki has released their second generation of video surveillance with 3 new cameras, AI-based video analytics, and 2 cloud-based storage...
Foolish Strategy: OEMing Facial Recognition on Dec 13, 2018
Almost as 'hot' as face recognition marketing right now is OEMing facial recognition. Last year, they were a who's who of company's with...

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