Reminds me of the "talking" drums used in West Africa[1]. Low frequency sound can travel distances measured in miles. [1] https://en.wikipedia.org/wiki/Talking

Reminds me of the "talking" drums used in West Africa[1]. Low frequency sound can travel distances measured in miles. [1] https://en.wikipedia.org/wiki/Talking_drum https://en.wikipedia.org/wiki/Talking_drum