Laryngophones and Osteophones
Military microphones have several distinct specifications according to the type of environment where they are used. They may need to clearly convey the voice of a person in a loud setting like the interior of an armoured vehicle or when in contact with the enemy. They may have to be integrated into an oxygen mask as is the case for aircrew. Similarly, they may need to detect very discreet voices such as troops whispering to avoid discovery.
Some personnel may use a throat microphone, also known as a laryngophone. A laryngophone uses a contact microphone positioned below a person’s larynx. The microphone will pick up vibrations resulting from the opening and closing of the glottis. These vibrations are converted into an electrical charge which is then transmitted by the radio. Likewise, an osteophone is worn on the head and exploits the conduction of sound from the inner ear through the skull.
Microphones for Electronic Communications
Warfare is a noisy business. Sailors, soldiers and air personnel rely on radio to communicate. They also need intercom systems to let them talk to each other in armoured vehicles, aircraft and ships. All voice electronic communications depend in some shape or form on a microphone.
A radio or intercom will be linked to a microphone. A microphone turns the sound of someone’s voice into an electrical signal so that it can be transmitted through the ether from a radio’s antenna. To understand how a microphone works we can use a hypothetical example. A person is using a radio to talk to someone else. They speak into their microphone which may be built into the radio or attached via a cable. Likewise, the microphone may be enclosed in a headset.
The microphone contains a diaphragm. This often takes the form of a thin material suspended at its edges. Sound is the result of vibrations. Vibrations produce an acoustic wave which propagates through the air. A person’s speech alters the air pressure in the path of their mouth as words and sounds leave their lips. The diaphragm will vibrate as it is hit by the different air pressures caused by the alterations in pressure. As the diaphragm is placed over a charged plate it will strike the latter. The plate releases an electrical charge every time this happens. These charges are sent by the radio to an antenna. As the current reaches the antenna it creates electrical and magnetic waves which form a radio signal.
When this signal reaches the receiving antenna it creates a charge. This charge is fed into the receiving radio and the process works in reverse. The sound is replicated by a speaker connected to the radio. Like the microphone, the speaker has a diaphragm which is connected to a magnetic coil. The incoming charge is fed into the magnetic coil. Another magnet is attached to the speaker cone. The charge is fed into the magnetic coil causing the speaker magnet to move. This movement disturbs the air in front of the speaker producing sound letting the other individual hear the person’s voice.