**155,000,000:** The estimated number of years ago that that sound production appeared in ray-finned fishes
**33:** The number of times sound evolved separately in the fish family tree
**1,500:** The number of virtual models of human listening developed by MIT neural network researchers in order to train an AI to spatially locate sound much as people do
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¹Footnotes: Fish: [sci-news.com](http://www.sci-news.com/biology/fish-sound-communication-10501.html). MIT: [mit.edu](https://news.mit.edu/2022/where-sound-come-from-model-0127) (Via Paul Roquet).
*Originally published in the January 31, 2022, edition of the This Week in Sound email newsletter [tinyletter.com/disquiet](https://tinyletter.com/disquiet).*