The word "anechoic" refers to an environment that doesn't reflect sound waves, making it completely silent. In contrast, the antonyms for anechoic are words that describe noisy or reflective environments. Some possible antonyms include cacophonous, loud, reverberant, echoing, and resonant. These words indicate spaces that are filled with sound, with noise bouncing off walls, floors, and furniture, resulting in a chaotic soundscape. While anechoic environments are used in scientific experiments and acoustic tests, noisy spaces are common in busy cities, concert halls, and sports arenas where sound is integral to the experience. Understanding these antonyms helps to differentiate between silent and noisy environments and can be useful when describing acoustic environments.