Sounds are inaudible usually because they are small, they take place where we cannot hear, or we cannot hear them unaided. Or so it would seem. For the Pythagoreans there were some remarkably loud sounds that were in effect everywhere, but that, for some reason, could be heard by no one. Aristotle characterized their argument this way:
“Some thinkers suppose that the motion of bodies of that [astronomical] size must produce a noise, since on our earth the motion of bodies far inferior in size and in speed of movement has the effect. Also, when the sun and the moon, they say, and all the stars, so great in number and in size, are moving with so rapid a motion, how should they not produce a sound inmensely great? Starting from this argument, and from the observation that their speeds, as measured by their distances, are in the same ratio as musical concordances, they assert that the sound given forth by the circular movementof the stars is a harmony.”
One response a Pythagorean could use when facing the quandary of a sound at once so large and yet so inaudible was to say that the sound is embodied and sounding all the time within every person - in other words, a constant aurality resulting in a pervasive deafness. Aristotle was still not convinced: “It appears unaccountable that we should not hear this music. They explain this by saying that the sound is in our ears from the very moment of birth and is thus indistinguishable from its contrary silence, since sound and silence are discriminated by mutual contrast… But, as we said before, melodious and poetical as the theory is, it cannot be a true account of the facts.” The Pythagorean did not maintain that absolutely no one could hear the music of the spheres. Some said that only one person -Pythagoras himself- could and that through his lone ability he discovered the phenomenon in the first place.
Kahn, Douglas (2001), Noise, WAter, Meat - A History of Sound in the Arts, Cambridge, The MIT Press.