This type of device is used not only in security or recording systems. Audio microphones are necessary when recording any special events on a video camera, so that after some time you can remember any event not only as a silent movie.
However, to ensure optimal sound quality and match the recorded image, it is recommended to select a microphone type that is most compatible with video equipment.
There are many varieties of this type of gadget in the electrical equipment market. For example, they are divided according to the method of placement relative to the video camera into:
Most popular video cameras are equipped with the former. However, they, as a rule, do not provide pure sound, since they are multi-sided, which means they equally record both the information that the camera tracks in its focus and extraneous noise behind the angle of its lens. For example, the video will show a conversation between two people, but in the audio, their speech will be drowned out by extraneous noise around them, including the singing of birds or the rumble of cars on the road.
The second, external devices for recording audio information, as a rule, are located outside the video camera. They can connect to it via a wire with a connector, and also transmit audio data to it via a separate communication channel. Microphones of this type, as a rule, record sound with better quality, firstly, because they do not skimp on them like built-in analogues, and secondly, due to the fact that they can be installed very close to the controlled object.
By design, such devices are also divided into types, for example, they are:
Devices for recording sound on a buttonhole are miniature in size, so they are often used for covert video recording. However, they are quite universal and can function with most recording devices, including video recorders.
Guns are the second type of such audio gadgets, which have the feature of directional capture of audio waves. They are used for particularly high-quality sound reproduction. Therefore, they have special screens in their design that act as noise filters.
The microphones also have the following markings:
Active, that is, having its own amplifier in its design, which allows you to receive a higher quality and more powerful sound signal for subsequent recording and playback.
Outdoor audio gadgets, as a rule, are equipped with noise filters, otherwise, due to the abundance of noise in the audio recorded, it is difficult to understand anything. They are also designed to withstand sudden fluctuations in noise, and even a sound shock, for example, from a sharp car horn, cannot disable them.
An analog microphone is a sound-sensitive membrane that can respond to sound vibrations in the surrounding space, converting them into a sound signal using an electromagnetic system.
The sensitivity of the device, which determines the area of effective capture of audio information. This parameter determines whether, at a certain distance from the recording object, his intelligible speech will be recorded or whether it will be drowned out by the noise of silence and interference located in the real, working radius of the device.
We recommend devices that have a built-in low-frequency noise filter to neutralize background technical noise, for example, from air conditioners, fans, refrigerator compressors, or passing cars.
The microphone is placed in a protective casing, which can significantly reduce the amount of interference in the recording. In this case, it will serve as an acoustic screen, reducing non-target noise coming from the back and sides of the device. This means that if the sound source is ideally located in front of the device, the sound recording will be cleaner.
The microphone sensitivity adjustment function allows you to use such a device in different conditions and environments, each time setting it up optimally.
It is recommended to use only external type devices in security systems. Because for this purpose, the video camera is located at a certain distance from the object of observation in order to ensure the maximum coverage angle of the recorded space, while the microphone must be located somewhere in the center of this area because it effectively captures sound only within a small radius around itself.
When using the built-in sound pickup directly on the camera, which in confined spaces is often mounted on a flat wall surface, which amplifies all background noise, it will not be possible to obtain high-quality sound recording.
A significant improvement in sound could be achieved by using several sound recording devices, but in video surveillance systems, even two-channel audio recording is extremely rarely supported; for example, video recorders record only single-channel audio.
As a result, we can conclude that the best option is an external microphone located in close proximity to the source of the recorded sound. This must be an active device that has the functions of pre-amplification and filtering of the signal from interference and distortion.
In order to choose the best option for equipment for a video surveillance system, you need to pay attention to its technical characteristics, application specifics, features, price and manufacturer’s brand.
Description:
Microphone model called Shorokh-7 Due to its small size, it is ideal even for covert surveillance systems.
The model of the device is no less high quality - MVK-MO22, also having miniature dimensions.
Often there is no need for complete independence and a long distance between the microphone and the camera, and the best option is a simple lavalier microphone, e.g. Audio-Technica ATR-3350 providing the best quality for its price.
Specifications:
Advantages and disadvantages:
Price:
The highest quality and most expensive microphone models are equipped with a special audio amplifier, which often has an auto-control function for audio preamplification.
Such equipment requires special power, which in some models is generally autonomous and does not come via a cable from the recording device, but from its own removable power source in the form of an electric battery. The amplifier significantly increases the effective distance of sound capture by the microphone and its further transmission via cable to the recording device.
An external microphone is connected to the video camera using a special cable with a plug at the end, which provides not only for the transmission of audio data from the device to the video equipment, but also from it to the video equipment, which ensures the operation of its filling, in the form of noise suppression filters and an amplifier.
Microphones "Rustle" are the most recognizable sound recording devices on the video surveillance market. Excellent characteristics and a fairly low price of the entire line allow you to choose a model for absolutely any purpose and task.
Let's look at the popular "Rustle" models and how to connect a microphone to a DVR and video camera.
The product line currently includes 8 models, which differ according to the following main criteria:
On video: Test of the popular microphone Shorokh-8
Connecting to a DVR
To connect a microphone, it is most convenient and reliable to use a KVK cable. On the microphone side, the yellow cable (sound) is connected to the central core (+), the blue cable is twisted with the braid (-) and the KVK power core (-), the red one is connected to the plus of the KVK cable power core. On the DVR side, under a special RCA connector, the central core of the KVK cable is screwed or soldered (depending on the connector), the braid is clamped in the holder. (The crimped connector is connected to the Audio in socket) All that remains is to connect the power wires of the KVK cable to a 12 volt power source and you can wiretap premises.
Connecting Rustle to an IP camera
Since the NVR recorder rarely contains an audio input, a microphone is connected to the camera (if such a function is supported). The connection diagram to the camera is no different, but depending on the camera connector, a special Jack 3.5 adapter may be required
All microphones in the line except Shorokh -1 can be installed anywhere: on the ceiling, in the baseboard, etc. thanks to the AGC and SWCH adjustments. Rustle -1 has no adjustment, and the useful radius of sound capture is up to 5 meters, so it is better to install this model directly in the sound zone.
Microphone rustling hidden in the ceiling But for analog CCTV systems there are a number of nuances. Starting from the transmission range of the audio signal, ending with the compatibility of audio output standards on the camera and on the DVR.
Considering that DVRs do not have two-channel inputs for recording sound, it is necessary to install lavalier microphones as close as possible to the object of observation.
If this is technically impossible, active shotgun microphones equipped with preamplifiers are used to reduce interference and distortion.
Rustle – 7– a microphone with a built-in amplifier, used for video surveillance systems, both for self-installation and when connected to a video camera.
Has an integrated automatic gain change function. This allows you to maintain a constant level of quality sound.
The maximum sensitivity of the device allows you to record audible, modulated sound from a distance of 7 m. The device has compact dimensions and an noise-resistant aluminum body, which allows for hidden installation or connection to dome cameras.
MVK-MO22– designed specifically for use in conjunction with analog and digital video cameras with a microphone input. Compatible with external cameras from the MVK Effio model range, manufactured by Byte Erg.
The small size allows you to install the microphone in the camera's thermal housing. An electret capsule is used as an active receiving element. The microphone connection diagram is two-wire, which allows you to transmit an audio stream over a distance of up to 1 km without amplifiers.
However, shielded and grounded cable should be used to prevent noise.
ATR-3350 by Audio-Technica. Refers to the lavalier type of microphones. The model can be completely independent not only from video cameras, but also from power supplies. The presented model can be powered by a button-type battery.
A three-wire circuit is used to connect to receiving devices via a Tulip-type RCA connector.
The first wire is connected in parallel to the same power source as the camera. The second wire is connected to the “leg” - the outer part of the RCA connector and in parallel to the negative terminal of the power supplied to the camera.
The third wire, transmitting the audio signal, is connected to the central terminal of the RCA connector. 
In practice, combined coaxial cables with a smaller cross-section are used than those used to transmit images from analog CCTV cameras. The cable size depends on the distance over which the audio signal needs to be transmitted.
With a minimum distance of up to 300 m, it is possible to use a thin combined cable of the ShVEV 3x0.12 brand; it is easy to install due to its flexibility, and its small diameter allows it to be laid in already installed mounting boxes.
For distances from 300 to 1000 m, the use of wires of at least 0.5 is required, for example KVK 2V 2x0.5 PVC.
If the audio signal is transmitted through a video camera line that has an input for connecting a microphone, then the pins will be wired to a 3.5 mm Mini-Jack plug.
The connection diagram is similar to the “tulip” plugs. The voltage supplied from the microphone is sufficient to transmit the signal to the camera's receiving devices, where they will be amplified before being transmitted to the DVR.
If the distance to the DVR exceeds 1000 m, then the transmission of the audio signal can be amplified by special devices.
DU-01 audio signal transmission amplifier, compatible with external microphones MD-012 and MD-015, which can be used in many camera models.
It has a wide range of transmitted frequencies - 20 Hz - 20 KHz. Compact dimensions - 13 x 85 x 40 mm allow installation at a remote camera installation point. And the operating temperature range -20 0 C…+50 0 C makes it possible to use outdoors.
However, for high-quality operation, the device requires a separate power line 7 - 24V, 4 mA.
Analog "MICRO"
Wireless CCTV with microphone. Battery life up to 4 hours from a Krona battery or any other comparable power source. The kit includes a signal receiving device that acts as a capture board.
It can be connected to a DVR - BNC connector, PC - USB adapter or to a TV - RCA connector. The range of receiving video and audio data is up to 50 m in line of sight conditions. The stream is transmitted at a frequency of 1.2 GHz.
It is possible to receive information from two cameras onto one receiving unit.
The camera operates as a simple signal repeater and does not have interference suppression devices. Focus adjustment is done manually and if the location changes, the adjustment must be done again.
The microphone sensitivity is up to 5 m; it has no filters or noise suppressors.
Digital Mini CCD Camera
Image quality 420 TV lines, with a minimum illumination of 0.5 lux, 1/3" SONY lens. It is possible to connect to a TV according to the PAL standard, power supply is constant voltage 12V.
Considering the high requirements for illumination and the size of the base and height of the dome - 90 mm (height), 114 mm (base diameter), the presented camera does not fall under the prohibitive standards of the legislation of the Russian Federation.
Removing the camera and microphone from the central unit on 1 m cables allows you to not only camouflage the device in a place well suited for shooting, but also install the microphone closer, where the quality of the recorded sound will be better.
The range of signal transmission via an “extension cable” without loss of image quality is no more than 35 m.
Before purchasing a microphone compatible with a CCTV camera, or a stand-alone device that will work on a public network, determine the level of required parameters:
The most common microphone today is from comcom, with the self-explanatory name “Rustle”. The manufacturer produces microphones with a cylindrical body made of nickel-plated aluminum.
The attached instructions state:
| Parameter | rustle-1 | rustle-7 | rustle-8 |
|---|---|---|---|
| Acoustic range | up to 5 meters | up to 7 meters | up to 10 meters |
| Line length | - up to 300 meters | ||
| Signal to noise ratio | 49 dB | 55dB | |
| Non-linear distortion factor | 0,5% | 0,3% | |
| AGC depth | No | 53dB | |
| AGC performance | No | 0.4 sec | |
| Output voltage | 0.25V | 0.60V | |
| Nutrition | DC5…12V | ||
| Operating temperature range | -10...+50°С | ||
| Dimensions | D10x35 mm | D10x47 mm | |
We will take a closer look at the Shorokh-7 microphone with a nickel-plated aluminum body.
You can use twisted pair cable over short distances up to 30-40 m. This distance is quite enough to install a microphone in a small store, home, or office. The problem with twisted pair wiring is the interference created by power wires and operating equipment. Some objects, even at short distances, may experience interference.
When viewing images from cameras, you want to not only see footage of what is happening, but also hear what they are saying. Nowadays, many DVR models have a microphone jack. Sometimes there is even a connector for each video camera.
This part of the article clearly shows diagrams for connecting a microphone to a DVR through different types of cable. When choosing a microphone, pay attention to the fact that microphones with AGC (automatic gain control) do not require adjustment, while microphones without AGC require adjustment.
At first glance, everything seems clear, The microphone is connected to the DVR using a “Tulip” type RCA connector.. But when it comes to implementation, questions arise. Where to solder, screw, secure what? Because all CCTV microphones sold do not have an RCA connector.
Let's take a closer look at the diagram for connecting a three-wire "rustle" microphone to the "Tulip" connector.
The red +12 V wire is connected to the /+/ power source, which can be a standard power supply or UPS. Almost always the microphone is connected to the power supply to which the camera is connected.
The blue "common" or negative wire is connected to the outer part of the RCA connector and to the /-/ terminal of the power supply.
The yellow "AUDIO" wire is connected to the center pin of the RCA connector.
The red +12V wire from the microphone is connected to the positive circuit of the power supply.
The blue wire “common” or negative from the microphone is simultaneously connected to the negative blue wire and then to the power source, and also in parallel to the braid of the combination cable and to the outer part of the RCA connector.
The yellow “audio” wire is connected to the central core, and then to the central contact of the tulip.
Diagram for connecting a microphone to computer speakers via a standard 3.5 mm mini-jack connector. The output voltage from the microphone is sufficient for direct connection to speakers, to the line-In connector of a computer, to a TV or other equipment.
Voltage on the IDE wires of the hard drive or floppy drive:
Pin assignments of the IDE hard drive power connector (presented in table form)
And remember: Art. 137 and art. 138 of the Criminal Code of the Russian Federation, the illegal collection or dissemination of information (acoustic information) about the private life of a person that constitutes his personal or family secret without his consent is prosecuted by law.
