An interesting thought struck me today, can sound be recovered? I mean sounds from the past, maybe a year or a millennium back.
Unlike electromagnetic energy, which can theoretically travel indefinitely in the vacuum of space, sound is a longitudinal mechanical wave of molecules and atoms. Sound is essentially kinetic energy. As it's spread over a large volume collisions with other atoms and molecule randomizes the kinetic energy so that it is no longer the coherent form of energy (longitudinal wave) we know as sound.
Bottom line: The energy of sound eventually becomes the random motion of atoms and molecules. I can't imagine it lasting for a year, no less a millennium.
Hope this helps.
can sound be recovered?
Yes, absolutely - if you know the exact waveform of the sound and the means to exactly reproduce the sound which include the perfect weather conditions, temperature, pressure, humidity, instruments, velocity at which the object emitting the sound was travelling at (Doppler Effect ), etc.
Theoretically yes, but practically, near impossible.