Although investigations of sound precede his, the work of Pythagoras, as described by his students and spiritual followers, set forth fundamental facts about how sound works. Pythagoras was active in Greece and Greek colonies in southern Italy during the decades surrounding 500 BCE and while every geometry student learns the theorem associated with his name, the essential equation was most likely known well before his time.
Pythagoras somehow skirted the publish or perish mandate for scholars because no writings of his are known to survive. Everything we know of his life, work, and teaching comes to us from documents in which his followers claim to be reporting first- or second-hand accounts of his thinking and instruction.
Medieval music theorists revered Pythagoras, and influential music treatises referred to him over the course of many centuries. They give credit to Pythagoras for identifying properties of sound waves and for expressing these numerically.