There are several synonyms for the word "quietens," which means to cause something or someone to become quiet or calm. One commonly used synonym is "calms," which specifically refers to soothing someone or something that is agitated. Another synonymous word is "silences," which implies completely stopping sound or noise. "Quiets" and "tranquilizes" are also synonyms that express the act of making something or someone less noisy or disruptive. Lastly, "pacifies" and "allays" also express the idea of reducing agitation and calming someone or something. The use of various synonyms can help writers to add more depth and variety to their writing, making it more appealing and interesting to readers.