Physicists have discovered the ultimate speed limit of sound

Fundamental constants place a new speed limit on sound

Scientists Find Sound's Highest Speed at 36 Km per Second

Gravitational Waves Detected, Confirming Einstein's Theory - The New York Times

Speed of sound, Description & Examples

Sound Waves - Nature, Speed, Reflection Of Sound With Formulas

Speed of light - Wikipedia

Was the Speed of Sound ever considered a theoretical speed limit? : r/askscience

An expanding universe is simulated in a quantum droplet – Physics World

Speed of Sound - Explanation, Speed of Sound in Different Media, FAQs

Sound, Properties, Types, & Facts