What are the Different Types of Audio Surveillance Equipment?

Erica Stratton

The are many types of audio surveillance equipment, but they fall into two broad categories of remote and physical. Wiretaps and some other kinds of listening devices require that an eavesdropper be physically present at some point. Other forms of audio surveillance are done remotely, through "bugs" or by subverting existing technologies that use wireless.

Audio surveillance equipment might be used by someone who suspects their partner of cheating.
Audio surveillance equipment might be used by someone who suspects their partner of cheating.

Wiretapping is one of the most well-known versions of audio surveillance equipment. Before wireless phone technology was invented, it involved creating an electrical connection between the subject's phone wire and the surveillance team's so that a conversation could be listened to in real time. This connection was called a "tap".

A phone tap may be used on a land line.
A phone tap may be used on a land line.

With the rise of wireless technology, all telephone conversations are tracked by computer. Telephone companies can have their computers perform a "digital switch", where a conversation's audio is copied to a second line. Though it is performed remotely, this kind of audio surveillance is still referred to as "wiretapping" and is almost impossible to trace.

Audio surveillance equipment may include headphones.
Audio surveillance equipment may include headphones.

Enhanced listening devices are a more hands-on form of audio surveillance equipment. A more advanced version of holding a drinking glass up to the wall, these microphones are designed to hear through walls, and an eavesdropper must physically be in the same building as the subject for them to be placed. Many of these devices primarily consist of a powerful microphone and headphones.

A bug is another common form of audio surveillance equipment. Bugs are tiny microphones equipped to send out information through radio waves. They can be hidden almost everywhere. In 1950, a bug was placed in a wooden replica of the Great Seal, used by the United States government to seal documents, and given in friendship to the U.S. Ambassador by Russia. It wasn't discovered until a decade later.

Miniature recorders are also a readily available form of audio surveillance equipment. Like bugs, they can be hidden in innocent objects such as pens or lapel buttons. Such devices can be purchased over the Internet, but laws vary as to how legal it is to own one.

Today, surveillance experts are finding ways to turn hand-held devices into audio surveillance equipment, rather than smuggling in bugs or training microphones on conversations. The Federal Bureau of Investigation (FBI) in the U.S. has the technology to remotely turn on a cell phone in a subject's pocket. Agents are then able to listen in on conversations being held in the vicinity. This method is called The Roving Bug.

In 2003, the Internal Revenue Service (IRS) in the U.S. discovered a way to listen in to a conversation through a car's emergency tracking system. The U.S. Court of Appeals for the Ninth Circuit prohibited this method of surveillance on the grounds that it disabled all of the car's security systems.

Audio surveillance may be used to record someone sharing secret information.
Audio surveillance may be used to record someone sharing secret information.

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Discussion Comments


Very nice explanation indeed! Whatever mentioned here about surveillance equipment is informative and educational as well. I think this is type of article readers look for reading. Audio surveillance devices are really good and people deserve to know more about this equipment.


I have always found audio surveillance devices to be fascinating because sound is such a delicate diffuse thing that it is really difficult to capture. It is one thing to think of getting photographs, but imagine using a satellite like device to record the conversations of someone that is hundreds or even thousands of feet away. It is like they are separating the air from the air. I hope they are not listening to me, but I am really impressed with the technology.


@truman12 - For what it is worth, there are laws in place that restrict when someone can access your conversations. And, even more reassuringly, most of us are too boring or insignificant to have our conversations recorded. I know it sounds harsh, but I like the fact that my life would be totally uninteresting to a spy. You can stay up all night worrying about who might be listening to you, but take comfort in the fact that there is probably nothing to hear.


Is it really that easy for someone to tap my phone? The phone company just flips a switch and all of a sudden they can hear and record everything I say? That is such a creepy thing to know about. They could be spying on any of us and we would have no idea.


I just have to mention one of my favorite movies, "The Conversation" directed by Francis Ford Copolla. The film follows Harry Lime, an audio surveillance expert who records a conversation he believes may be used for sinister purposes. It is one of the hallmarks of paranoid 70s cinema and an incredible portrait of the then still infantile audio surveillance industry. The movie is filled with technical explanations and demonstrations of very specialized equipment but somehow manages to be riveting. It must be a favorite of audio surveillance experts.

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