Water sports wrote in message
...

What doors block high frequiences , wood type, door type ??

Probably hollow doors filled with fibreglass or something
similar, shreds of varying lengths. The specifications of
what you want are those opposite to specs for a loudspeaker
diaphragm, i.e. non-rigid, to absorb sound rather than pass
it on, etc.

--
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)