Understanding the Behavior of Sound
In this article, I will attempt to show you how to detect transmitters, bugs and other miniature microphone devices that may have been inserted in your own house or office. Let us first understand the dynamics of sound. Sound always takes the path of least resistance, such as a doorway, duct or open window. If someone wants to spy on you, he or she may most likely have placed their bugs in overlooked air paths such as over, under or around doors. Sometimes you can find holes in walls, or spaces around pipes and wiring. Remember even the smallest air path can transmit sound to a microphone.
Sound-as well as electrical signals-travels along the metal surfaces of electrical conduits, pipes and ducts. You can recover this sound after it has traveled more than 100 feet in this manner. Water-filled pipes transmit sound with much less distortion than empty pipes.
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Sounds, depending on their frequencies, penetrate floors, ceilings and doors. After sound energy hits a structure, some reflects from the surface, some is absorbed and the rest passes on. Remember even a so-called ”soundproof’ room can be bugged by your enemies especially if the soundproofing consists of acoustical tile. Truth is, acoustical tile can actually reduce a room’s sound security. Acoustical tile was made to reduce sound reverberations in a recording studio. Tile lets walls absorb more sound, reducing its level in the room. Sound that is absorbed is not lost because energy cannot be destroyed, only converted. Therefore, acoustical tile may reduce a room’s security by allowing sound to be transmitted through the wall structure and it is often applied in a hanging configuration allowing space to place surveillance gear above the tile.
Most microphones will hear through acoustical tile quite well, if not simply punch a small hole with a nail or dentists drill. A small camera can also be placed behind these tiles because the tiny holes on the acoustical walls can easily relay video information to your enemies.
Distortion and Interference
Sound waves not only travel from their source, they also are reflected when they hit a surface. Reflected sounds behave as if the surface they hit is their original source, and can be reflected again. Sound patterns become very complicated after reflecting and re-reflecting from ceilings, floors, walls and internal objects. Reflected sound waves can merge almost exactly with sounds arriving from the first source. Sounds merged like this have an increased sound level and are in phase. Sound is distorted when a disruption changes its normally smooth pattern. Distortion may be encountered before the sound is recorded, during the recording or at playback. Excessive distortion cuts down the recovery and understanding of intercepted sound. Which is why your enemies will take great care to place their bugs in distortion-free places only.
When placing the microphone, they will consider how quickly sound loses power after leaving its source. Say your friend is talking to you from 10 feet away. If you then stand 20 feet apart, the magnitude of his voice doesn't become one-half as loud-it cuts to one-fourth! The magnitude of sound declines according to the inverse square law. If you quadruple the distance between you and your friend, the power of the sound of his voice drops to one-sixteenth. In surveillance work we are interested in two kinds of sound: Sounds usually voices we want to hear, and all other unwanted sounds no matter what their origin. Types of sound interference are countless. Rain, plumbing, air conditioning, fans, traffic, planes and trains are just some of the problems. When you are being monitored, just one more person speaking in the near vicinity can cause massive interference.
Sometimes original and reflected sound waves meet so that their decompression and compression neutralize each other. When they merge this way the sounds are out of phase. If neutralization is perfect, the effect is called cancellation. Sounds are rarely totally out of phase, so the nullification effect is usually just called interference.
Bugging Rule No. 1 – Place mics Close
best bug sweeping experts India Whether hard wiring, stashing a recorder or placing a transmitter, the prime rule of your enemies will be: place the microphone as close as possible to the people speaking. The average male’s speaking voice falls between a frequency range of 100 Hz and 8 KHz and the average female’s between 200 Hz and 10KHz. Most speech falls between 600 Hz and 4 KHz. You can sharply reduce interference without sacrificing clarity and understanding by reducing the power of frequencies between 600 Hz and 4 KHz. Some recording systems come with low pass and high pass filters that limit the band pass to achieve this reduction, automatically reducing sounds outside of the voice range. Early telephones did this by virtue of their carbon microphone construction. Rooms constructed with hard surface walls and containing filing cabinets, desks and other such furnishings are known as “hard rooms.” Hard rooms reflect sound waves a great deal, creating a feeling of loudness despite a lack of loud sounds. On the other hand, “soft rooms” are fitted with acoustical tiles, soft. walls, padded furniture, drapes and carpets. Soft rooms absorb sounds and cause a feeling of quiet regardless of the presence of loud sounds.
Soft rooms pose fewer surveillance problems than do hard rooms. Hard rooms reflect sound more, causing distortion. By its construction, a hard room’s structure multiplies the effects of disturbances and interference. If your enemy has had the time and opportunity chances are that he would have tested several spots in the target room to find the one with the least amount of annoying distortion. Some operatives take a surreptitious photo of the room on an earlier reconnaissance visit and then pre-plan the actual placement by experience or by experimenting with a similar room. This is often possible if the target room is a motel room or apartment with duplicates nearby.
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Amit Sen, a commercial pilot by training, has over 15 years experience in the space of corporate investigations, handling Copyright & Trademark infringement cases, Pre – employment verification Industrial Espionage investigations, Asset & Net – Worth assessment assignments and vendor / supplier verification cases, among others. Co-founder of Alliance One – who are the best de bugging and espionage detectives in India. Amit has also successfully completed assignments in a wide range of sectors, including the machine tools industry, pharmaceutical industry, hospitality sector, specialized equipment (Oil & natural gas sector, aviation industry etc.), telecom industry & the IT & ITes sectors. These cases have all involved both offline and online investigations.
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