‘Past sounds’ provides a history of sound from the origin of sound waves 300,000 years after the Big Bang to the modern day of ultrasound and electroacoustic technology. Primordial sound was of a very low frequency, but powerful and omnipresent, and the environment in which the first living things evolved was an acoustically rich one, profoundly affecting the forms, habits, and destinies of those creatures. Hearing evolution is described along with the human development of music and musical instruments. The Greeks built amphitheatres that dealt with the practicalities of sound and Pythagoras studied harmony on a monochord. The World Wars of the twentieth century accelerated electronics development and inspired underwater acoustic research and sonar systems.