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Microphone is a generic term that refers to any
element that transforms acoustic energy (sound) into
electrical energy (electricity (audio signal).
What do
former President Bill Clinton and Pete Townsend of the
Who have in common?
Answer!
Types
of Microphones
Dynamic
microphones - A dynamic microphone takes advantage
of electromagnet
effects. When a magnet moves past a wire (or coil of
wire), the magnet induces current to flow in the wire.
In a dynamic microphone, the diaphragm moves either a
magnet or a coil when sound waves hit the diaphragm,
and the movement creates a small current.
Condenser microphones - A condenser microphone
is essentially a capacitor,
with one plate of the capacitor moving in response to
sound waves. The movement changes the capacitance of
the capacitor, and these changes are amplified to
create a measurable signal. Condenser microphones
usually need a small battery
to provide a voltage
across the capacitor.
Condenser
microphones need a source of power to impress the
charge on the capacitor. One of three methods is used.
Either a battery will be inserted inside the
microphone, a permanent charge is retained on
the diaphragm or back plate, or phantom
power is used.
Phantom power is the supply of power through the
ground cable of an XLR cable. Ranging from 9
volts to 52 volts, typically 48 volts,
this power can be put into the cable either from a
mixer, a phantom power box or a battery
pack. A mixer might have a button that allows phantom
power through the ground cable. A phantom power
box is like an intermediate component between a
mixer and a mic. It is a box connected to the mains
that essentially just puts a charge on the ground
cable. A battery pack does exactly the same
thing, but works only with batteries instead of mains
power.
Guide
to Microphones
Older Microphones
Explained
Ribbon
microphones -
In a ribbon microphone, a thin ribbon is suspended in
a magnetic field. Sound waves move the ribbon which
changes the current flowing through it.
Carbon
microphones - The oldest and
simplest microphone uses carbon dust. This is the
technology used in the first telephones
and is still used in some telephones today. The carbon
dust has a thin metal or plastic diaphragm on one
side. As sound waves hit the diaphragm, they compress
the carbon dust, which changes its resistance. By
running a current through the carbon, the changing
resistance changes the amount of current that flows.
See How
Telephones Work for more information.
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