If you're looking for alternative ways to describe a sound that is "barely audible," there are a variety of words and phrases that could work. Some of the most common synonyms include "faint," "quiet," "muffled," "soft," "low," "hushed," and "whispered." Other options might include "barely perceptible," "hard to hear," "subdued," "muted," "diminished," "fleeting," or "almost inaudible." Depending on the context and tone of your writing, different synonyms might be more or less appropriate, so it's worth experimenting with a few different options to see what fits best.