Neither having nor producing echoes: an anechoic chamber. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "anechoic" in a sentence
"The Charlotte’s “dead room”—designed after a similar structure at Bell Laboratories—was what was formally known as an anechoic chamber."
"The so-called anechoic chamber, which measures nearly 36-feet long, is made of special material that absorbs electromagnetic waves."
"Apple's website, the labs consist of 17 antenna characterisation, or "anechoic", chambers that are used to measure overall antenna performance."