<s>
A	O
microphone	O
,	O
colloquially	O
called	O
mic	O
or	O
mike	O
(	O
)	O
,	O
is	O
a	O
transducer	B-Algorithm
that	O
converts	O
sound	O
into	O
an	O
electrical	O
signal	O
.	O
</s>
<s>
They	O
are	O
also	O
used	O
in	O
computers	O
for	O
recording	O
voice	O
,	O
speech	B-Application
recognition	I-Application
,	O
VoIP	B-Application
,	O
and	O
for	O
other	O
purposes	O
such	O
as	O
ultrasonic	O
sensors	O
or	O
knock	O
sensors	O
.	O
</s>
<s>
The	O
most	O
common	O
are	O
the	O
dynamic	O
microphone	O
,	O
which	O
uses	O
a	O
coil	O
of	O
wire	O
suspended	O
in	O
a	O
magnetic	O
field	O
;	O
the	O
condenser	O
microphone	O
,	O
which	O
uses	O
the	O
vibrating	O
diaphragm	B-Device
as	O
a	O
capacitor	O
plate	O
;	O
and	O
the	O
contact	B-Algorithm
microphone	I-Algorithm
,	O
which	O
uses	O
a	O
crystal	O
of	O
piezoelectric	O
material	O
.	O
</s>
<s>
Microphones	O
typically	O
need	O
to	O
be	O
connected	O
to	O
a	O
preamplifier	B-Algorithm
before	O
the	O
signal	O
can	O
be	O
recorded	O
or	O
reproduced	O
.	O
</s>
<s>
Speaking	O
of	O
his	O
device	O
,	O
Meucci	O
wrote	O
in	O
1857	O
,	O
"	O
It	O
consists	O
of	O
a	O
vibrating	O
diaphragm	B-Device
and	O
an	O
electrified	O
magnet	O
with	O
a	O
spiral	O
wire	O
that	O
wraps	O
around	O
it	O
.	O
</s>
<s>
The	O
vibrating	O
diaphragm	B-Device
alters	O
the	O
current	O
of	O
the	O
magnet	O
.	O
</s>
<s>
These	O
alterations	O
of	O
current	O
,	O
transmitted	O
to	O
the	O
other	O
end	O
of	O
the	O
wire	O
,	O
create	O
analogous	O
vibrations	O
of	O
the	O
receiving	O
diaphragm	B-Device
and	O
reproduce	O
the	O
word.	O
"	O
</s>
<s>
Better	O
results	O
were	O
achieved	O
in	O
1876	O
with	O
the	O
"	O
liquid	O
transmitter	O
"	O
design	O
in	O
early	O
telephones	O
from	O
Alexander	O
Graham	O
Bell	O
and	O
Elisha	O
Gray	O
–	O
the	O
diaphragm	B-Device
was	O
attached	O
to	O
a	O
conductive	O
rod	O
in	O
an	O
acid	O
solution	O
.	O
</s>
<s>
This	O
microphone	O
was	O
employed	O
at	O
the	O
first	O
radio	O
broadcast	B-Operating_System
ever	O
,	O
a	O
performance	O
at	O
the	O
New	O
York	O
Metropolitan	O
Opera	O
House	O
in	O
1910	O
.	O
</s>
<s>
Also	O
in	O
1923	O
,	O
the	O
ribbon	B-Algorithm
microphone	I-Algorithm
was	O
introduced	O
,	O
another	O
electromagnetic	O
type	O
,	O
believed	O
to	O
have	O
been	O
developed	O
by	O
Harry	O
F	O
.	O
Olson	O
,	O
who	O
applied	O
the	O
concept	O
used	O
in	O
a	O
ribbon	O
speaker	O
to	O
making	O
a	O
microphone	O
.	O
</s>
<s>
During	O
the	O
second	O
half	O
of	O
the	O
20th	O
century	O
,	O
development	O
advanced	O
quickly	O
with	O
the	O
Shure	O
Brothers	O
bringing	O
out	O
the	O
SM58	B-Algorithm
and	O
SM57	B-Algorithm
.	O
</s>
<s>
The	O
sensitive	O
transducer	B-Algorithm
element	O
of	O
a	O
microphone	O
is	O
called	O
its	O
element	O
or	O
capsule	O
.	O
</s>
<s>
Sound	O
is	O
first	O
converted	O
to	O
mechanical	O
motion	O
by	O
means	O
of	O
a	O
diaphragm	B-Device
,	O
the	O
motion	O
of	O
which	O
is	O
then	O
converted	O
to	O
an	O
electrical	O
signal	O
.	O
</s>
<s>
A	O
wireless	B-Device
microphone	I-Device
contains	O
a	O
radio	O
transmitter	O
.	O
</s>
<s>
Microphones	O
are	O
categorized	O
by	O
their	O
transducer	B-Algorithm
principle	O
,	O
such	O
as	O
condenser	O
,	O
dynamic	O
,	O
etc.	O
,	O
and	O
by	O
their	O
directional	O
characteristics	O
.	O
</s>
<s>
Sometimes	O
other	O
characteristics	O
such	O
as	O
diaphragm	B-Device
size	O
,	O
intended	O
use	O
or	O
orientation	O
of	O
the	O
principal	O
sound	O
input	O
to	O
the	O
principal	O
axis	O
(	O
end	O
-	O
or	O
side-address	O
)	O
of	O
the	O
microphone	O
are	O
used	O
to	O
describe	O
the	O
microphone	O
.	O
</s>
<s>
The	O
diaphragm	B-Device
acts	O
as	O
one	O
plate	O
of	O
a	O
capacitor	O
,	O
and	O
audio	O
vibrations	O
produce	O
changes	O
in	O
the	O
distance	O
between	O
the	O
plates	O
.	O
</s>
<s>
Condenser	O
microphones	O
require	O
a	O
power	O
source	O
,	O
provided	O
either	O
via	O
microphone	O
inputs	O
on	O
equipment	O
as	O
phantom	B-Algorithm
power	I-Algorithm
or	O
from	O
a	O
small	O
battery	O
.	O
</s>
<s>
Condenser	O
microphones	O
are	O
also	O
available	O
with	O
two	O
diaphragms	B-Device
that	O
can	O
be	O
electrically	O
connected	O
to	O
provide	O
a	O
range	O
of	O
polar	O
patterns	O
(	O
see	O
below	O
)	O
,	O
such	O
as	O
cardioid	O
,	O
omnidirectional	O
,	O
and	O
figure-eight	O
.	O
</s>
<s>
There	O
are	O
two	O
main	O
categories	O
of	O
condenser	O
microphones	O
,	O
depending	O
on	O
the	O
method	O
of	O
extracting	O
the	O
audio	O
signal	O
from	O
the	O
transducer	B-Algorithm
:	O
DC-biased	O
microphones	O
,	O
and	O
radio	O
frequency	O
(	O
RF	O
)	O
or	O
high	O
frequency	O
(	O
HF	O
)	O
condenser	O
microphones	O
.	O
</s>
<s>
Note	O
that	O
the	O
time	O
constant	O
of	O
an	O
RC	B-Algorithm
circuit	I-Algorithm
equals	O
the	O
product	O
of	O
the	O
resistance	O
and	O
capacitance	O
.	O
</s>
<s>
The	O
signal	O
from	O
the	O
oscillator	O
may	O
either	O
be	O
amplitude	O
modulated	O
by	O
the	O
capacitance	O
changes	O
produced	O
by	O
the	O
sound	O
waves	O
moving	O
the	O
capsule	O
diaphragm	B-Device
,	O
or	O
the	O
capsule	O
may	O
be	O
part	O
of	O
a	O
resonant	O
circuit	O
that	O
modulates	O
the	O
frequency	O
of	O
the	O
oscillator	O
signal	O
.	O
</s>
<s>
The	O
absence	O
of	O
a	O
high	O
bias	O
voltage	O
permits	O
the	O
use	O
of	O
a	O
diaphragm	B-Device
with	O
looser	O
tension	O
,	O
which	O
may	O
be	O
used	O
to	O
achieve	O
wider	O
frequency	O
response	O
due	O
to	O
higher	O
compliance	O
.	O
</s>
<s>
They	O
are	O
used	O
in	O
many	O
applications	O
,	O
from	O
high-quality	O
recording	O
and	O
lavalier	B-Algorithm
(	O
lapel	B-Algorithm
mic	I-Algorithm
)	O
use	O
to	O
built-in	O
microphones	O
in	O
small	O
sound	O
recording	O
devices	O
and	O
telephones	O
.	O
</s>
<s>
Prior	O
to	O
the	O
proliferation	O
of	O
MEMS	B-Architecture
microphones	O
,	O
nearly	O
all	O
cell-phone	O
,	O
computer	O
,	O
PDA	O
and	O
headset	O
microphones	O
were	O
electret	O
types	O
.	O
</s>
<s>
Unlike	O
other	O
capacitor	O
microphones	O
,	O
they	O
require	O
no	O
polarizing	O
voltage	O
,	O
but	O
often	O
contain	O
an	O
integrated	O
preamplifier	B-Algorithm
that	O
does	O
require	O
power	O
(	O
often	O
incorrectly	O
called	O
polarizing	O
power	O
or	O
bias	O
)	O
.	O
</s>
<s>
This	O
preamplifier	B-Algorithm
is	O
frequently	O
phantom	O
powered	O
in	O
sound	O
reinforcement	O
and	O
studio	O
applications	O
.	O
</s>
<s>
Monophonic	O
microphones	O
designed	O
for	O
personal	B-Device
computers	I-Device
(	O
PCs	B-Device
)	O
,	O
sometimes	O
called	O
multimedia	O
microphones	O
,	O
use	O
a	O
3.5mm	O
plug	O
as	O
usually	O
used	O
,	O
without	O
power	O
,	O
for	O
stereo	O
;	O
the	O
ring	O
,	O
instead	O
of	O
carrying	O
the	O
signal	O
for	O
a	O
second	O
channel	O
,	O
carries	O
power	O
via	O
a	O
resistor	O
from	O
(	O
normally	O
)	O
a	O
5V	O
supply	O
in	O
the	O
computer	O
.	O
</s>
<s>
A	O
valve	B-Algorithm
microphone	I-Algorithm
is	O
a	O
condenser	O
microphone	O
that	O
uses	O
a	O
vacuum	O
tube	O
(	O
valve	O
)	O
amplifier	O
.	O
</s>
<s>
A	O
small	O
movable	O
induction	O
coil	O
,	O
positioned	O
in	O
the	O
magnetic	O
field	O
of	O
a	O
permanent	O
magnet	O
,	O
is	O
attached	O
to	O
the	O
diaphragm	B-Device
.	O
</s>
<s>
When	O
sound	O
enters	O
through	O
the	O
windscreen	O
of	O
the	O
microphone	O
,	O
the	O
sound	O
wave	O
moves	O
the	O
diaphragm	B-Device
.	O
</s>
<s>
When	O
the	O
diaphragm	B-Device
vibrates	O
,	O
the	O
coil	O
moves	O
in	O
the	O
magnetic	O
field	O
,	O
producing	O
a	O
varying	O
current	O
in	O
the	O
coil	O
through	O
electromagnetic	O
induction	O
.	O
</s>
<s>
Ribbon	B-Algorithm
microphones	I-Algorithm
use	O
a	O
thin	O
,	O
usually	O
corrugated	O
metal	O
ribbon	O
suspended	O
in	O
a	O
magnetic	O
field	O
.	O
</s>
<s>
Ribbon	B-Algorithm
microphones	I-Algorithm
are	O
similar	O
to	O
moving	O
coil	O
microphones	O
in	O
the	O
sense	O
that	O
both	O
produce	O
sound	O
by	O
means	O
of	O
magnetic	O
induction	O
.	O
</s>
<s>
Basic	O
ribbon	B-Algorithm
microphones	I-Algorithm
detect	O
sound	O
in	O
a	O
bi-directional	O
(	O
also	O
called	O
figure-eight	O
,	O
as	O
in	O
the	O
diagram	O
below	O
)	O
pattern	O
because	O
the	O
ribbon	O
is	O
open	O
on	O
both	O
sides	O
.	O
</s>
<s>
Though	O
the	O
symmetrical	O
front	O
and	O
rear	O
pickup	O
can	O
be	O
a	O
nuisance	O
in	O
normal	O
stereo	O
recording	O
,	O
the	O
high	O
side	O
rejection	O
can	O
be	O
used	O
to	O
advantage	O
by	O
positioning	O
a	O
ribbon	B-Algorithm
microphone	I-Algorithm
horizontally	O
,	O
for	O
example	O
above	O
cymbals	O
,	O
so	O
that	O
the	O
rear	O
lobe	O
picks	O
up	O
sound	O
only	O
from	O
the	O
cymbals	O
.	O
</s>
<s>
Crossed	O
figure	O
8	O
,	O
or	O
Blumlein	O
pair	O
,	O
stereo	O
recording	O
is	O
gaining	O
in	O
popularity	O
,	O
and	O
the	O
figure-eight	O
response	O
of	O
a	O
ribbon	B-Algorithm
microphone	I-Algorithm
is	O
ideal	O
for	O
that	O
application	O
.	O
</s>
<s>
The	O
classic	O
RCA	B-Algorithm
Type	I-Algorithm
77-DX	I-Algorithm
microphone	I-Algorithm
has	O
several	O
externally	O
adjustable	O
positions	O
of	O
the	O
internal	O
baffle	O
,	O
allowing	O
the	O
selection	O
of	O
several	O
response	O
patterns	O
ranging	O
from	O
"	O
figure-eight	O
"	O
to	O
"	O
unidirectional	O
"	O
.	O
</s>
<s>
Such	O
older	O
ribbon	B-Algorithm
microphones	I-Algorithm
,	O
some	O
of	O
which	O
still	O
provide	O
high-quality	O
sound	O
reproduction	O
,	O
were	O
once	O
valued	O
for	O
this	O
reason	O
,	O
but	O
a	O
good	O
low-frequency	O
response	O
could	O
be	O
obtained	O
only	O
when	O
the	O
ribbon	O
was	O
suspended	O
very	O
loosely	O
,	O
which	O
made	O
them	O
relatively	O
fragile	O
.	O
</s>
<s>
Modern	O
ribbon	O
materials	O
,	O
including	O
new	O
nanomaterials	O
,	O
have	O
now	O
been	O
introduced	O
that	O
eliminate	O
those	O
concerns	O
and	O
even	O
improve	O
the	O
effective	O
dynamic	O
range	O
of	O
ribbon	B-Algorithm
microphones	I-Algorithm
at	O
low	O
frequencies	O
.	O
</s>
<s>
In	O
common	O
with	O
other	O
classes	O
of	O
dynamic	O
microphone	O
,	O
ribbon	B-Algorithm
microphones	I-Algorithm
do	O
n't	O
require	O
phantom	B-Algorithm
power	I-Algorithm
;	O
in	O
fact	O
,	O
this	O
voltage	O
can	O
damage	O
some	O
older	O
ribbon	B-Algorithm
microphones	I-Algorithm
.	O
</s>
<s>
Some	O
new	O
modern	O
ribbon	B-Algorithm
microphone	I-Algorithm
designs	O
incorporate	O
a	O
preamplifier	B-Algorithm
and	O
,	O
therefore	O
,	O
do	O
require	O
phantom	B-Algorithm
power	I-Algorithm
,	O
and	O
circuits	O
of	O
modern	O
passive	O
ribbon	B-Algorithm
microphones	I-Algorithm
(	O
i.e.	O
</s>
<s>
those	O
without	O
the	O
aforementioned	O
preamplifier	B-Algorithm
)	O
are	O
specifically	O
designed	O
to	O
resist	O
damage	O
to	O
the	O
ribbon	O
and	O
transformer	B-Algorithm
by	O
phantom	B-Algorithm
power	I-Algorithm
.	O
</s>
<s>
Also	O
there	O
are	O
new	O
ribbon	O
materials	O
available	O
that	O
are	O
immune	O
to	O
wind	O
blasts	O
and	O
phantom	B-Algorithm
power	I-Algorithm
.	O
</s>
<s>
One	O
of	O
the	O
plates	O
,	O
the	O
diaphragm	B-Device
,	O
vibrates	O
in	O
sympathy	O
with	O
incident	O
sound	O
waves	O
,	O
applying	O
a	O
varying	O
pressure	O
to	O
the	O
carbon	O
.	O
</s>
<s>
A	O
crystal	O
microphone	O
or	O
piezo	B-Algorithm
microphone	I-Algorithm
uses	O
the	O
phenomenon	O
of	O
piezoelectricity	O
—	O
the	O
ability	O
of	O
some	O
materials	O
to	O
produce	O
a	O
voltage	O
when	O
subjected	O
to	O
pressure	O
—	O
to	O
convert	O
vibrations	O
into	O
an	O
electrical	O
signal	O
.	O
</s>
<s>
An	O
example	O
of	O
this	O
is	O
potassium	O
sodium	O
tartrate	O
,	O
which	O
is	O
a	O
piezoelectric	O
crystal	O
that	O
works	O
as	O
a	O
transducer	B-Algorithm
,	O
both	O
as	O
a	O
microphone	O
and	O
as	O
a	O
slimline	O
loudspeaker	O
component	O
.	O
</s>
<s>
They	O
were	O
difficult	O
to	O
match	O
to	O
early	O
transistor	B-Application
equipment	O
and	O
were	O
quickly	O
supplanted	O
by	O
dynamic	O
microphones	O
for	O
a	O
time	O
,	O
and	O
later	O
small	O
electret	O
condenser	O
devices	O
.	O
</s>
<s>
Piezoelectric	O
transducers	B-Algorithm
are	O
often	O
used	O
as	O
contact	B-Algorithm
microphones	I-Algorithm
to	O
amplify	O
sound	O
from	O
acoustic	O
musical	O
instruments	O
,	O
to	O
sense	O
drum	O
hits	O
,	O
for	O
triggering	O
electronic	O
samples	O
,	O
and	O
to	O
record	O
sound	O
in	O
challenging	O
environments	O
,	O
such	O
as	O
underwater	O
under	O
high	O
pressure	O
.	O
</s>
<s>
A	O
fiber-optic	B-Architecture
microphone	O
converts	O
acoustic	O
waves	O
into	O
electrical	O
signals	O
by	O
sensing	O
changes	O
in	O
light	O
intensity	O
,	O
instead	O
of	O
sensing	O
changes	O
in	O
capacitance	O
or	O
magnetic	O
fields	O
as	O
with	O
conventional	O
microphones	O
.	O
</s>
<s>
During	O
operation	O
,	O
light	O
from	O
a	O
laser	O
source	O
travels	O
through	O
an	O
optical	B-Architecture
fiber	I-Architecture
to	O
illuminate	O
the	O
surface	O
of	O
a	O
reflective	O
diaphragm	B-Device
.	O
</s>
<s>
Sound	O
vibrations	O
of	O
the	O
diaphragm	B-Device
modulate	O
the	O
intensity	O
of	O
light	O
reflecting	O
off	O
the	O
diaphragm	B-Device
in	O
a	O
specific	O
direction	O
.	O
</s>
<s>
The	O
modulated	O
light	O
is	O
then	O
transmitted	O
over	O
a	O
second	O
optical	B-Architecture
fiber	I-Architecture
to	O
a	O
photodetector	O
,	O
which	O
transforms	O
the	O
intensity-modulated	O
light	O
into	O
analog	O
or	O
digital	O
audio	O
for	O
transmission	O
or	O
recording	O
.	O
</s>
<s>
Fiber-optic	B-Architecture
microphones	O
possess	O
high	O
dynamic	O
and	O
frequency	O
range	O
,	O
similar	O
to	O
the	O
best	O
high	O
fidelity	O
conventional	O
microphones	O
.	O
</s>
<s>
Fiber-optic	B-Architecture
microphones	O
do	O
not	O
react	O
to	O
or	O
influence	O
any	O
electrical	O
,	O
magnetic	O
,	O
electrostatic	O
or	O
radioactive	O
fields	O
(	O
this	O
is	O
called	O
EMI/RFI	O
immunity	O
)	O
.	O
</s>
<s>
The	O
fiber-optic	B-Architecture
microphone	O
design	O
is	O
therefore	O
ideal	O
for	O
use	O
in	O
areas	O
where	O
conventional	O
microphones	O
are	O
ineffective	O
or	O
dangerous	O
,	O
such	O
as	O
inside	O
industrial	O
turbines	O
or	O
in	O
magnetic	O
resonance	O
imaging	O
(	O
MRI	O
)	O
equipment	O
environments	O
.	O
</s>
<s>
Fiber-optic	B-Architecture
microphones	O
are	O
robust	O
,	O
resistant	O
to	O
environmental	O
changes	O
in	O
heat	O
and	O
moisture	O
,	O
and	O
can	O
be	O
produced	O
for	O
any	O
directionality	O
or	O
impedance	O
matching	O
.	O
</s>
<s>
The	O
distance	O
between	O
the	O
microphone	O
's	O
light	O
source	O
and	O
its	O
photodetector	O
may	O
be	O
up	O
to	O
several	O
kilometers	O
without	O
need	O
for	O
any	O
preamplifier	B-Algorithm
or	O
another	O
electrical	O
device	O
,	O
making	O
fiber-optic	B-Architecture
microphones	O
suitable	O
for	O
industrial	O
and	O
surveillance	O
acoustic	O
monitoring	O
.	O
</s>
<s>
Fiber-optic	B-Architecture
microphones	O
are	O
used	O
in	O
very	O
specific	O
application	O
areas	O
such	O
as	O
for	O
infrasound	O
monitoring	O
and	O
noise	B-Algorithm
cancellation	I-Algorithm
.	O
</s>
<s>
Other	O
uses	O
include	O
industrial	O
equipment	O
monitoring	O
and	O
audio	O
calibration	B-General_Concept
and	O
measurement	O
,	O
high-fidelity	O
recording	O
and	O
law	O
enforcement	O
.	O
</s>
<s>
A	O
sound	O
wave	O
caused	O
the	O
diaphragm	B-Device
to	O
move	O
,	O
forcing	O
a	O
needle	O
to	O
move	O
up	O
and	O
down	O
in	O
the	O
water	O
.	O
</s>
<s>
The	O
MEMS	B-Architecture
(	O
microelectromechanical	B-Architecture
systems	I-Architecture
)	O
microphone	O
is	O
also	O
called	O
a	O
microphone	O
chip	O
or	O
silicon	O
microphone	O
.	O
</s>
<s>
A	O
pressure-sensitive	O
diaphragm	B-Device
is	O
etched	O
directly	O
into	O
a	O
silicon	O
wafer	O
by	O
MEMS	B-Architecture
processing	O
techniques	O
and	O
is	O
usually	O
accompanied	O
with	O
an	O
integrated	O
preamplifier	B-Algorithm
.	O
</s>
<s>
Most	O
MEMS	B-Architecture
microphones	O
are	O
variants	O
of	O
the	O
condenser	O
microphone	O
design	O
.	O
</s>
<s>
Digital	O
MEMS	B-Architecture
microphones	O
have	O
built-in	O
analog-to-digital	O
converter	O
(	O
ADC	O
)	O
circuits	O
on	O
the	O
same	O
CMOS	O
chip	O
making	O
the	O
chip	O
a	O
digital	O
microphone	O
and	O
so	O
more	O
readily	O
integrated	O
with	O
modern	O
digital	O
products	O
.	O
</s>
<s>
Major	O
manufacturers	O
producing	O
MEMS	B-Architecture
silicon	O
microphones	O
are	O
Wolfson	O
Microelectronics	O
(	O
WM7xxx	O
)	O
now	O
Cirrus	O
Logic	O
,	O
InvenSense	O
(	O
product	O
line	O
sold	O
by	O
Analog	O
Devices	O
)	O
,	O
Akustica	O
(	O
AKU200x	O
)	O
,	O
Infineon	O
(	O
SMM310	O
product	O
)	O
,	O
Knowles	O
Electronics	O
,	O
Memstech	O
(	O
MSMx	O
)	O
,	O
NXP	O
Semiconductors	O
(	O
division	O
bought	O
by	O
Knowles	O
)	O
,	O
Sonion	O
MEMS	B-Architecture
,	O
Vesper	O
,	O
AAC	O
Acoustic	O
Technologies	O
,	O
and	O
Omron	O
.	O
</s>
<s>
More	O
recently	O
,	O
since	O
the	O
2010s	O
,	O
there	O
has	O
been	O
increased	O
interest	O
and	O
research	O
into	O
making	O
piezoelectric	O
MEMS	B-Architecture
microphones	O
which	O
are	O
a	O
significant	O
architectural	O
and	O
material	O
change	O
from	O
existing	O
condenser	O
style	O
MEMS	B-Architecture
designs	O
.	O
</s>
<s>
A	O
loudspeaker	O
,	O
a	O
transducer	B-Algorithm
that	O
turns	O
an	O
electrical	O
signal	O
into	O
sound	O
waves	O
,	O
is	O
the	O
functional	O
opposite	O
of	O
a	O
microphone	O
.	O
</s>
<s>
Since	O
a	O
conventional	O
speaker	O
is	O
similar	O
in	O
construction	O
to	O
a	O
dynamic	O
microphone	O
(	O
with	O
a	O
diaphragm	B-Device
,	O
coil	O
and	O
magnet	O
)	O
,	O
speakers	O
can	O
actually	O
work	O
"	O
in	O
reverse	O
"	O
as	O
microphones	O
.	O
</s>
<s>
In	O
practical	O
use	O
,	O
speakers	O
are	O
sometimes	O
used	O
as	O
microphones	O
in	O
applications	O
where	O
high	O
bandwidth	O
and	O
sensitivity	O
are	O
not	O
needed	O
such	O
as	O
intercoms	O
,	O
walkie-talkies	B-Application
or	O
video	O
game	O
voice	O
chat	O
peripherals	O
,	O
or	O
when	O
conventional	O
microphones	O
are	O
in	O
short	O
supply	O
.	O
</s>
<s>
However	O
,	O
there	O
is	O
at	O
least	O
one	O
practical	O
application	O
that	O
exploits	O
those	O
weaknesses	O
:	O
the	O
use	O
of	O
a	O
medium-size	O
woofer	B-Device
placed	O
closely	O
in	O
front	O
of	O
a	O
"	O
kick	O
drum	O
"	O
(	O
bass	O
drum	O
)	O
in	O
a	O
drum	O
set	O
to	O
act	O
as	O
a	O
microphone	O
.	O
</s>
<s>
A	O
commercial	O
product	O
example	O
is	O
the	O
Yamaha	O
Subkick	O
,	O
a	O
woofer	B-Device
shock-mounted	O
into	O
a	O
10	O
"	O
drum	O
shell	O
used	O
in	O
front	O
of	O
kick	O
drums	O
.	O
</s>
<s>
A	O
pressure	O
microphone	O
uses	O
a	O
diaphragm	B-Device
between	O
a	O
fixed	O
internal	O
volume	O
of	O
air	O
and	O
the	O
environment	O
and	O
responds	O
uniformly	O
to	O
pressure	O
from	O
all	O
directions	O
,	O
so	O
it	O
is	O
said	O
to	O
be	O
omnidirectional	O
.	O
</s>
<s>
A	O
pressure-gradient	O
microphone	O
uses	O
a	O
diaphragm	B-Device
that	O
is	O
at	O
least	O
partially	O
open	O
on	O
both	O
sides	O
.	O
</s>
<s>
For	O
small	O
diaphragm	B-Device
microphones	O
such	O
as	O
the	O
Shure	O
(	O
also	O
pictured	O
above	O
)	O
,	O
it	O
usually	O
extends	O
from	O
the	O
axis	O
of	O
the	O
microphone	O
commonly	O
known	O
as	O
"	O
end	O
fire	O
"	O
or	O
"	O
top/end	O
address	O
"	O
.	O
</s>
<s>
The	O
cardioid	O
response	O
reduces	O
pickup	O
from	O
the	O
side	O
and	O
rear	O
,	O
helping	O
to	O
avoid	O
feedback	O
from	O
the	O
monitors	B-Device
.	O
</s>
<s>
Since	O
these	O
directional	O
transducer	B-Algorithm
microphones	O
achieve	O
their	O
patterns	O
by	O
sensing	O
pressure	O
gradient	O
,	O
putting	O
them	O
very	O
close	O
to	O
the	O
sound	O
source	O
(	O
at	O
distances	O
of	O
a	O
few	O
centimeters	O
)	O
results	O
in	O
a	O
bass	O
boost	O
due	O
to	O
the	O
increased	O
gradient	O
.	O
</s>
<s>
The	O
SM58	B-Algorithm
has	O
been	O
the	O
most	O
commonly	O
used	O
microphone	O
for	O
live	O
vocals	O
for	O
more	O
than	O
50	O
years	O
demonstrating	O
the	O
importance	O
and	O
popularity	O
of	O
cardioid	O
mics	O
.	O
</s>
<s>
Most	O
ribbon	B-Algorithm
microphones	I-Algorithm
are	O
of	O
this	O
pattern	O
.	O
</s>
<s>
In	O
more	O
mathematical	O
terms	O
,	O
while	O
omnidirectional	O
microphones	O
are	O
scalar	O
transducers	B-Algorithm
responding	O
to	O
pressure	O
from	O
any	O
direction	O
,	O
bi-directional	O
microphones	O
are	O
vector	O
transducers	B-Algorithm
responding	O
to	O
the	O
gradient	O
along	O
an	O
axis	O
normal	O
to	O
the	O
plane	O
of	O
the	O
diaphragm	B-Device
.	O
</s>
<s>
Sound	O
engineers	O
Ed	O
Long	O
and	O
Ron	O
Wickersham	O
developed	O
the	O
concept	O
of	O
placing	O
the	O
diaphragm	B-Device
parallel	O
to	O
and	O
facing	O
the	O
boundary	O
.	O
</s>
<s>
While	O
the	O
patent	O
has	O
expired	O
,	O
"	O
Pressure	O
Zone	O
Microphone	O
"	O
and	O
"	O
PZM	B-Algorithm
"	O
are	O
still	O
active	O
trademarks	O
of	O
Crown	O
International	O
,	O
and	O
the	O
generic	O
term	O
boundary	B-Algorithm
microphone	I-Algorithm
is	O
preferred	O
.	O
</s>
<s>
While	O
a	O
boundary	B-Algorithm
microphone	I-Algorithm
was	O
initially	O
implemented	O
using	O
an	O
omnidirectional	O
element	O
,	O
it	O
is	O
also	O
possible	O
to	O
mount	O
a	O
directional	O
microphone	O
close	O
enough	O
to	O
the	O
surface	O
to	O
gain	O
some	O
of	O
the	O
benefits	O
of	O
this	O
technique	O
while	O
retaining	O
the	O
directional	O
properties	O
of	O
the	O
element	O
.	O
</s>
<s>
A	O
lavalier	B-Algorithm
microphone	I-Algorithm
is	O
made	O
for	O
hands-free	O
operation	O
.	O
</s>
<s>
The	O
lavalier	B-Algorithm
cord	O
may	O
be	O
hidden	O
by	O
clothes	O
and	O
either	O
run	O
to	O
an	O
RF	O
transmitter	O
in	O
a	O
pocket	O
or	O
clipped	O
to	O
a	O
belt	O
(	O
for	O
mobile	O
use	O
)	O
,	O
or	O
run	O
directly	O
to	O
the	O
mixer	O
(	O
for	O
stationary	O
applications	O
)	O
.	O
</s>
<s>
A	O
wireless	B-Device
microphone	I-Device
transmits	O
the	O
audio	O
as	O
a	O
radio	O
or	O
optical	O
signal	O
rather	O
than	O
via	O
a	O
cable	O
.	O
</s>
<s>
A	O
contact	B-Algorithm
microphone	I-Algorithm
picks	O
up	O
vibrations	O
directly	O
from	O
a	O
solid	O
surface	O
or	O
object	O
,	O
as	O
opposed	O
to	O
sound	O
vibrations	O
carried	O
through	O
air	O
.	O
</s>
<s>
The	O
microphone	O
commonly	O
consists	O
of	O
a	O
magnetic	O
(	O
moving	O
coil	O
)	O
transducer	B-Algorithm
,	O
contact	O
plate	O
and	O
contact	O
pin	O
.	O
</s>
<s>
Contact	B-Algorithm
microphones	I-Algorithm
have	O
been	O
used	O
to	O
pick	O
up	O
the	O
sound	O
of	O
a	O
snail	O
's	O
heartbeat	O
and	O
the	O
footsteps	O
of	O
ants	O
.	O
</s>
<s>
A	O
throat	B-Algorithm
microphone	I-Algorithm
is	O
a	O
variant	O
of	O
the	O
contact	B-Algorithm
microphone	I-Algorithm
that	O
picks	O
up	O
speech	O
directly	O
from	O
a	O
person	O
's	O
throat	O
,	O
which	O
it	O
is	O
strapped	O
to	O
.	O
</s>
<s>
A	O
stereo	O
microphone	O
is	O
often	O
used	O
for	O
broadcast	B-Operating_System
applications	O
or	O
field	O
recording	O
where	O
it	O
would	O
be	O
impractical	O
to	O
configure	O
two	O
separate	O
condenser	O
microphones	O
in	O
a	O
classic	O
X-Y	O
configuration	O
(	O
see	O
microphone	B-Algorithm
practice	I-Algorithm
)	O
for	O
stereophonic	O
recording	O
.	O
</s>
<s>
A	O
noise-canceling	B-Algorithm
microphone	I-Algorithm
is	O
a	O
highly	O
directional	O
design	O
intended	O
for	O
noisy	O
environments	O
.	O
</s>
<s>
Many	O
noise-canceling	B-Algorithm
microphones	I-Algorithm
combine	O
signals	O
received	O
from	O
two	O
diaphragms	B-Device
that	O
are	O
in	O
opposite	O
electrical	O
polarity	O
or	O
are	O
processed	O
electronically	O
.	O
</s>
<s>
In	O
dual	O
diaphragm	B-Device
designs	O
,	O
the	O
main	O
diaphragm	B-Device
is	O
mounted	O
closest	O
to	O
the	O
intended	O
source	O
and	O
the	O
second	O
is	O
positioned	O
farther	O
away	O
from	O
the	O
source	O
so	O
that	O
it	O
can	O
pick	O
up	O
environmental	O
sounds	O
to	O
be	O
subtracted	O
from	O
the	O
main	O
diaphragm	B-Device
's	O
signal	O
.	O
</s>
<s>
Other	O
noise-canceling	O
designs	O
use	O
one	O
diaphragm	B-Device
that	O
is	O
affected	O
by	O
ports	O
open	O
to	O
the	O
sides	O
and	O
rear	O
of	O
the	O
microphone	O
,	O
with	O
the	O
sum	O
being	O
a	O
16dB	O
rejection	O
of	O
sounds	O
that	O
are	O
farther	O
away	O
.	O
</s>
<s>
One	O
noise-canceling	O
headset	O
design	O
using	O
a	O
single	O
diaphragm	B-Device
has	O
been	O
used	O
prominently	O
by	O
vocal	O
artists	O
such	O
as	O
Garth	O
Brooks	O
and	O
Janet	O
Jackson	O
.	O
</s>
<s>
A	O
few	O
noise-canceling	B-Algorithm
microphones	I-Algorithm
are	O
throat	B-Algorithm
microphones	I-Algorithm
.	O
</s>
<s>
The	O
two	O
dominant	O
methods	O
were	O
initially	O
defined	O
in	O
German	O
DIN	O
45595	O
as	O
:de:Tonaderspeisung	O
or	O
T-power	O
and	O
DIN	O
45596	O
for	O
phantom	B-Algorithm
power	I-Algorithm
.	O
</s>
<s>
Since	O
the	O
1980s	O
,	O
phantom	B-Algorithm
power	I-Algorithm
has	O
become	O
much	O
more	O
common	O
,	O
because	O
the	O
same	O
input	O
may	O
be	O
used	O
for	O
both	O
powered	O
and	O
unpowered	O
microphones	O
.	O
</s>
<s>
inch	O
(	O
sometimes	O
referred	O
to	O
as	O
6.35mm	O
)	O
phone	B-Device
connector	I-Device
on	O
less	O
expensive	O
musician	O
's	O
microphones	O
,	O
using	O
an	O
unbalanced	O
TS	O
(	O
tip	O
and	O
sleeve	O
)	O
phone	B-Device
connector	I-Device
.	O
</s>
<s>
3.5	O
mm	O
(	O
sometimes	O
referred	O
to	O
as	O
inch	O
mini	O
)	O
TRS	O
(	O
tip	B-Device
,	I-Device
ring	I-Device
and	I-Device
sleeve	I-Device
)	O
stereo	O
(	O
also	O
available	O
as	O
TS	O
mono	O
)	O
mini	O
phone	O
plug	O
on	O
prosumer	O
camera	O
,	O
recorder	O
and	O
computer	O
microphones	O
.	O
</s>
<s>
USB	B-Protocol
allows	O
direct	O
connection	O
to	O
PCs	B-Device
.	O
</s>
<s>
Electronics	O
in	O
these	O
microphones	O
powered	O
over	O
the	O
USB	B-Protocol
connection	O
performs	O
preamplification	O
and	O
ADC	O
before	O
the	O
digital	O
audio	O
data	O
is	O
transferred	O
via	O
the	O
USB	B-Protocol
interface	O
.	O
</s>
<s>
Some	O
lavalier	B-Algorithm
(	O
or	O
"	O
lapel	O
"	O
,	O
from	O
the	O
days	O
of	O
attaching	O
the	O
microphone	O
to	O
the	O
news	O
reporter	O
's	O
suit	O
lapel	O
)	O
microphones	O
use	O
a	O
proprietary	O
connector	O
for	O
connection	O
to	O
a	O
wireless	O
transmitter	O
,	O
such	O
as	O
a	O
radio	O
pack	O
.	O
</s>
<s>
Since	O
2005	O
,	O
professional-quality	O
microphones	O
with	O
USB	B-Protocol
connections	O
have	O
begun	O
to	O
appear	O
,	O
designed	O
for	O
direct	O
recording	O
into	O
computer-based	O
software	O
.	O
</s>
<s>
Professional	O
vacuum-tube	O
sound	O
equipment	O
incorporates	O
a	O
transformer	B-Algorithm
that	O
steps	O
up	O
the	O
impedance	O
of	O
the	O
microphone	O
circuit	O
to	O
the	O
high	O
impedance	O
and	O
voltage	O
needed	O
to	O
drive	O
the	O
input	O
tube	O
.	O
</s>
<s>
External	O
step-up	O
transformers	B-Algorithm
are	O
also	O
available	O
that	O
can	O
be	O
used	O
in-line	O
between	O
a	O
low	O
impedance	O
microphone	O
and	O
a	O
high	O
impedance	O
input	O
.	O
</s>
<s>
This	O
is	O
a	O
practical	O
concern	O
but	O
is	O
not	O
directly	O
an	O
indication	O
of	O
the	O
microphone	O
's	O
quality	O
,	O
and	O
in	O
fact	O
the	O
term	O
sensitivity	O
is	O
something	O
of	O
a	O
misnomer	O
,	O
"	O
transduction	B-Algorithm
gain	O
"	O
being	O
perhaps	O
more	O
meaningful	O
,	O
(	O
or	O
just	O
"	O
output	O
level	O
"	O
)	O
because	O
true	O
sensitivity	O
is	O
generally	O
set	O
by	O
the	O
noise	O
floor	O
,	O
and	O
too	O
much	O
"	O
sensitivity	O
"	O
in	O
terms	O
of	O
output	O
level	O
compromises	O
the	O
clipping	O
level	O
.	O
</s>
<s>
These	O
are	O
calibrated	O
transducers	B-Algorithm
and	O
are	O
usually	O
supplied	O
with	O
a	O
calibration	B-General_Concept
certificate	O
that	O
states	O
absolute	O
sensitivity	O
against	O
frequency	O
.	O
</s>
<s>
Since	O
this	O
may	O
change	O
over	O
the	O
lifetime	O
of	O
the	O
device	O
,	O
it	O
is	O
necessary	O
to	O
regularly	O
calibrate	B-General_Concept
measurement	O
microphones	O
.	O
</s>
<s>
All	O
microphone	O
calibration	B-General_Concept
is	O
ultimately	O
traceable	O
to	O
primary	O
standards	O
at	O
a	O
national	O
measurement	O
institute	O
such	O
as	O
NPL	O
in	O
the	O
UK	O
,	O
PTB	O
in	O
Germany	O
and	O
NIST	O
in	O
the	O
United	O
States	O
,	O
which	O
most	O
commonly	O
calibrate	B-General_Concept
using	O
the	O
reciprocity	O
primary	O
standard	O
.	O
</s>
<s>
Measurement	O
microphones	O
calibrated	O
using	O
this	O
method	O
can	O
then	O
be	O
used	O
to	O
calibrate	B-General_Concept
other	O
microphones	O
using	O
comparison	O
calibration	B-General_Concept
techniques	O
.	O
</s>
<s>
A	O
microphone	O
array	O
is	O
any	O
number	O
of	O
microphones	O
operating	O
in	O
tandem	B-Application
.	O
</s>
<s>
Typically	O
,	O
an	O
array	O
is	O
made	O
up	O
of	O
omnidirectional	O
microphones	O
distributed	O
about	O
the	O
perimeter	B-Application
of	O
a	O
space	O
,	O
linked	O
to	O
a	O
computer	O
that	O
records	O
and	O
interprets	O
the	O
results	O
into	O
a	O
coherent	O
form	O
.	O
</s>
