"Rhythmic sounds" refers to a pattern or beat that is created by sounds occurring at regular intervals. It means that the sounds follow a consistent and predictable pattern or rhythm. Full definition
Feel the sand beneath your bare feet as you walk along the edge of the water, listening to the soothing rhythmic sound of the waves. (resortsandlodges.com)
To do that, play rhythmic sounds like isochronic tones. (mindbodygreen.com)
Standing outside in the chilly New York air, I could hear a low rhythmic sound emanating from a wooden, box - like structure in the courtyard below. (dallasnews.com)