What is an Anechoic Chamber?
An anechoic chamber is a shielded room designed to suppress sound and/or electromagnetic energy. It is designed to suppress the electromagnetic wave energy of echoes such as reflected electromagnetic waves from the internal surfaces and to provide effective isolation from the acoustic or RF noise present in the external environment. The chamber is isolated from outside noise, vibration, and emissions so that nothing can leak in and they are often floating on special mounts to prevent any unwanted noise or vibration from getting through.
Acoustic or RF anechoic chambers are used to determine the EMC and/or external sound susceptibility of products before launching them into the market for commercial use. The chambers range from small carton-size box like the size of household microwave ovens to ones as large to accommodate aircraft hangars. The size of the chamber depends on the size of the objects and frequency ranges to be tested.Anechoic chambers are also used to measure to accurately measure an antenna’s gain, efficiency, and radiation patterns. These antennas are vital components for communication of almost all devices ranging from satellites, military vehicles, aircrafts, mobile phones, etc. The chambers are also used to test radiations for medical devices such as X-ray, MRI, CT-scan machines, etc.
In order to make the anechoic chambers free of reflection, the interior surfaces of the RF anechoic chamber are covered with radiation absorbent material (RAM). The most common absorber is made of carbon loaded foam shaped like a pyramid. Sharp tips on the absorbers help to absorb RF waves without letting them from bouncing off. Due to its shape, the amount of RF that bounces off anechoic chamber walls is often 0.1% to 1% (-30 to -20 dB) of the original wave.