Beethoven's problem has been described in many speech and hearing journals
by world renowned experts.  There actually is a fair amount of agreement
about the result.  Only the cause is left to debate.

He couldn't hear much through these tricks because he wasn't confronted
with silence.  Beethoven was suffering from a form of deafness that
caused him to have a constant hissing and roaring noise.  He was problem
overwhelmed some of the time from the noise that he sensed all the time.

Ray Bayles