The word ‘anechoic’ means simply ‘without echo’. An anechoic chamber is a box, chamber or room that is devoid of reflections from the walls, ceiling, or floor. If you’ve ever been in a large room and shouted ‘echo!’, you’ll know that you usually get some kind of reverberation where you hear your voice repeat a few times. To avoid this phenomena, anechoic chambers are lined on the inside with materials that are designed to completely absorb all sound waves thus eliminating any and all reflections.
RF & EMI/EMC Anechoic Testing Chambers – What Are They and How Do They Work?