Donaghy, Michael: Cage,

the composer, locked in a soundproof room in Harvard.
Heard his heartbeat and the sound of Niagara Falls.
Produced by the operation of his nervous system,
From which he derived a theory, no doubt.

Me, I heard a throaty click at the end of ″wedlock."
And Niagara on the long distance line.
I knew a couple once, went up there on their honeymoon.
After a week, they said, you don't even hear it.