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Custom-made plugs
April 1st 2008 Custom-made earplugs such
as the Emtec Noisebreaker
tend to be personally
moulded and vented. A
silicone rubber moulding is
moulded to each individual
concha bowl and ear canal.
The plug incorporates a
central drilled channel in
which a filter is placed
which allows pressure
equalisation but presents a
finite impedance to the
passage of audio frequency
sounds.
The acoustic filter
attenuates all sounds going
to the ear, but attenuates
more in the mid-band range
(about 1 to 6kHZ). A through
hole in the 'ear plug' means
the wearer is not completely
isolated; conversation and
warning signals may be
heard. Noisebreakers can be
worn under helmets or
breathing apparatus.
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