In article , The CO
writes
It's also *very* possible it was 'washed' in the process of putting it
into electronic format
to make it clearer. This is quite trivial to do and can make a bad
recording sound
significantly better, simply by eliminating the audio frequency 'notch'
that (mostly) contains the noise.

Maybe they were using filters on the recording equipment? If the first
thing an experienced Lanc crewman says when planning the idea is "You
can't hear anything over the engines, and there's this awful hiss from
the intercom..." it would make sense to me.

--
John