Bone Conducting Helmet System
|Bone conduction, as a method
to facilitate hearing in people with outer ear or conductive
hearing loss, was discovered in the 16th century. At that
time, it was considered a novelty, of little worth. A
century later, two deafness specialists started using
this technique to assist patients, and in 1879, the Rhodes
Audiophone, which used a vulcanite fan to pick up air
vibrations and transmit them to the teeth, was patented.
One of the first real commercial hearing aids, the Audiphone
was the essential tool for the hard of hearing, until
the modern carbon electric devices were developed.
But what is bone conduction?
Simply put, it's the reason a person's own voice sounds different
to them when they hear a recording of them speaking. Their
vocal chords, when vibrating, cause the bones they are connected
to to vibrate, which expands through your skull to the small
bones in your ears. Since standard hearing works by the eardrums
being vibrated by audio pressure waves which in turn shake
these tiny bones, bone conduction bypasses the need for sound
waves to create something audible.
Many theatres have removed
the massive subwoofers from their sound systems and replaced
them with resonators. These are basically low frequency drivers
with no cone, but bolted to the floor so that as long as you
are in contact with the floor, you will 'hear' and 'feel'
the bass, but without the ear-damaging sound pressure waves
normal subs create.
It's actually safer than normal speakers.
Since there is no physical vibration hitting a person's eardrums,
there is less chance of exposure damage.
So, why are the military and police in the
world so excited?
a subvocalization-ready microphone with a bone conduction
speaker in a headset, and the person in the field can
have a full, realtime communication system that, to
them, is normal speech and hearing, but it makes virtually
no sound. In a tactical situation, operating in a sensitive
environment, communication is usually handled by whisper
or hand signals for most operators across the various
groups that work in tactical operations. This is a limited
level of communication, as careful audio pickups will
catch whispers, and hand signals, while very effective,
are also very limited in the level of complexity expressable.
Another advantage of bone conduction as a speaker replacement
is that since it does not use your outer ear, the conductor
can be placed on the cheekbone near the ear, leaving
the wearer's ears able to hear normal, ambient sound
with no interference from the headset.
In civilian circles, bone conduction is
used for everything from coin-sized cellular telephones, which
operate by merely holding next to your cheekbone and voice
dialing, to dentist's chairs that conduct soothing music into
patients. A company in Sydney, Australia uses bone conduction
headsets from a supplier to US special forces teams, in their
operation of climbs up the Sydney harbour bridge. The headsets
allow for instruction by the climb leaders to the climbers,
but does not interfere with the natural sounds and conversation
inherent to a tour trip.
This is just one more fantastic example
of an old idea being reworked to keep operators, whether civilian,
police or military, safer and more effective in the field.