The term "stentorious" refers to a loud and powerful voice, often with a booming quality. Antonyms for this adjective would be words that describe a softer, more delicate, or even whispered tone. Some possible antonyms might include "quiet," "hushed," "murmured," "whispered," "sibilant," "mellifluous," "ethereal," or "gentle." Using these words in contrast to "stentorious" can help create a sense of contrast or juxtaposition in writing, and can be useful for describing everything from the sound of a person's voice to the volume of a musical performance or the ambiance of a particular environment.