In the study of waves, while testing any sensitive equipment for its sound level or electromagnetic emission, there is often an external disturbance in the form of unwanted noise, radio waves, or electromagnetic waves. Due to this interference, the results get altered, and the tester can end up with wrong deductions.
To tackle this issue, anechoic chambers were created. The first anechoic chamber was designed in 1943 by Leo Beranek and Harvey Sleeper to absorb the reflections of sound, radio, and electromagnetic waves.
What are Anechoic Chambers?
A protective chamber called an anechoic chamber is intended to dampen electromagnetic radiation or sound. Originally, anechoic chambers were first used to absorb acoustic (sound) echoes brought on by a room's internal reflections. More recently, they have been used to create an insulated atmosphere for radio frequency (RF) and microwaves.
Additionally, anechoic chambers are frequently shielded from outside energy interference. By combining these two effects, a detector can only pick up direct sounds, replicating being outside in a free field. An interesting fact about an anechoic chamber is that a person standing in the room would be able to hear the sound of some of their organs, i.e., the sound of one's heart pumping, stomach gurgling, and air breathing in and out of the lungs.
Types of Anechoic Chambers
Anechoic chambers can be divided into two categories:
- Acoustic chambers: have walls coated with fiberglass sound absorbers to reduce echoes.
- Shielded rooms: have interior surfaces treated with radio wave absorbers. Common absorbers can be foam pyramids loaded with conductive carbon or ferrite tiles for upper-frequency testing in shielded rooms.
What are Radio Anechoic Rooms?
Radio anechoic rooms are special anechoic rooms that are specifically designed to absorb electromagnetic waves. These rooms are lined with radiation-absorbent material, or RAM, that efficiently absorbs electromagnetic waves. These spaces are made up of little pyramids created by soaking rubberized insulation foam in a conductible metal, such as iron.
Electromagnetic waves hit the pyramids and bounce off to the nearby pyramids, dissipating all of their energy in a mechanism that is still very similar to how sound waves absorb. In addition, a Faraday Cage, a mesh of conducting material that inhibits radiation from entering the chamber, is used to shield such rooms from radiation from outside sources.
Importance of Anechoic Chambers
The importance of anechoic chambers rises daily due to the level of sensitivity and accuracy scientists are trying to achieve in their acoustic and radio testing.
- For EMC (electromagnetic compatibility) testing, a high-performance anechoic chamber with exceptional traceability and reproducibility is crucial.
- The anechoic chamber has developed into a potent tool utilized in product development and is no longer just a straightforward evaluation tool.
- Radio anechoic chambers test radar, antennas, and electromagnetic interference from various sources.
- It is utilized in huge concert halls to absorb any vibration from loud noises that might harm the structure or its occupants.
- Anechoic Chambers are preferred over OATs (open-air test sites) because the latter is not an accurate environment for testing sound due to external interference.