BACKGROUND: Army scientists have found that some combat helmets
are better than others in helping soldiers determine the
location of sounds in their environment. Certain older helmet
designs can degrade a soldier's ability to tell where a sound is
coming from, which can be dangerous in combat. HOW WE HEAR:
Sound is a mechanical wave, meaning it produces vibrational
energy in the medium through which it moves, such as air. The
ear detects sound waves and sends those signals to the brain for
processing. The incoming sound waves cause the eardrum to
vibrate, and this sends mechanical waves vibrating through a
fluid inside a narrow tube called the cochlea. The cochlea
vibrates tiny hairs tuned to specific pitches or frequencies of
the sound. The hair vibrations stimulate nerves, which in turn
send signals to the brain. It's similar to how a microphone
works, in which sound vibrates a membrane, causing electrical
signals to travel through a wire to an electronic circuit card
for processing. DETERMINING DIRECTION: