<s>
A	O
microphone	B-Application
,	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>
Microphones	B-Application
are	O
used	O
in	O
many	O
applications	O
such	O
as	O
telephones	O
,	O
hearing	O
aids	O
,	O
public	O
address	O
systems	O
for	O
concert	O
halls	O
and	O
public	O
events	O
,	O
motion	O
picture	O
production	O
,	O
live	O
and	O
recorded	O
audio	O
engineering	O
,	O
sound	O
recording	O
,	O
two-way	O
radios	O
,	O
megaphones	O
,	O
and	O
radio	O
and	O
television	O
broadcasting	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>
Several	O
types	O
of	O
microphone	B-Application
are	O
used	O
today	O
,	O
which	O
employ	O
different	O
methods	O
to	O
convert	O
the	O
air	O
pressure	O
variations	O
of	O
a	O
sound	O
wave	O
to	O
an	O
electrical	O
signal	O
.	O
</s>
<s>
The	O
most	O
common	O
are	O
the	O
dynamic	O
microphone	B-Application
,	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	B-Application
,	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	B-Application
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>
In	O
1856	O
,	O
Italian	O
inventor	O
Antonio	O
Meucci	O
developed	O
a	O
dynamic	O
microphone	B-Application
based	O
on	O
the	O
generation	O
of	O
electric	O
current	O
by	O
moving	O
a	O
coil	O
of	O
wire	O
to	O
various	O
depths	O
in	O
a	O
magnetic	O
field	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>
The	O
first	O
microphone	B-Application
that	O
enabled	O
proper	O
voice	O
telephony	O
was	O
the	O
(	O
loose-contact	O
)	O
carbon	O
microphone	B-Application
.	O
</s>
<s>
The	O
Berliner	O
microphone	B-Application
found	O
commercial	O
success	O
through	O
the	O
use	O
by	O
Alexander	O
Graham	O
Bell	O
for	O
his	O
telephone	O
and	O
Berliner	O
became	O
employed	O
by	O
Bell	O
.	O
</s>
<s>
The	O
carbon	O
microphone	B-Application
was	O
critical	O
in	O
the	O
development	O
of	O
telephony	O
,	O
broadcasting	O
and	O
the	O
recording	O
industries	O
.	O
</s>
<s>
Thomas	O
Edison	O
refined	O
the	O
carbon	O
microphone	B-Application
into	O
his	O
carbon-button	O
transmitter	O
of	O
1886	O
.	O
</s>
<s>
This	O
microphone	B-Application
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>
Wente	O
of	O
Western	O
Electric	O
developed	O
the	O
next	O
breakthrough	O
with	O
the	O
first	O
condenser	O
microphone	B-Application
.	O
</s>
<s>
In	O
1923	O
,	O
the	O
first	O
practical	O
moving	O
coil	O
microphone	B-Application
was	O
built	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	B-Application
.	O
</s>
<s>
Over	O
the	O
years	O
these	O
microphones	B-Application
were	O
developed	O
by	O
several	O
companies	O
,	O
most	O
notably	O
RCA	O
that	O
made	O
large	O
advancements	O
in	O
pattern	O
control	O
,	O
to	O
give	O
the	O
microphone	B-Application
directionality	O
.	O
</s>
<s>
With	O
television	O
and	O
film	O
technology	O
booming	O
there	O
was	O
a	O
demand	O
for	O
high-fidelity	O
microphones	B-Application
and	O
greater	O
directionality	O
.	O
</s>
<s>
Electro-Voice	O
responded	O
with	O
their	O
Academy	O
Award-winning	O
shotgun	O
microphone	B-Application
in	O
1963	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	B-Application
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
complete	O
microphone	B-Application
also	O
includes	O
a	O
housing	O
,	O
some	O
means	O
of	O
bringing	O
the	O
signal	O
from	O
the	O
element	O
to	O
other	O
equipment	O
,	O
and	O
often	O
an	O
electronic	O
circuit	O
to	O
adapt	O
the	O
output	O
of	O
the	O
capsule	O
to	O
the	O
equipment	O
being	O
driven	O
.	O
</s>
<s>
A	O
wireless	B-Device
microphone	I-Device
contains	O
a	O
radio	O
transmitter	O
.	O
</s>
<s>
Microphones	B-Application
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	B-Application
are	O
used	O
to	O
describe	O
the	O
microphone	B-Application
.	O
</s>
<s>
The	O
condenser	O
microphone	B-Application
,	O
invented	O
at	O
Western	O
Electric	O
in	O
1916	O
by	O
E	O
.	O
C	O
.	O
Wente	O
,	O
is	O
also	O
called	O
a	O
capacitor	O
microphone	B-Application
or	O
electrostatic	O
microphone	B-Application
—	O
capacitors	O
were	O
historically	O
called	O
condensers	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	B-Application
span	O
the	O
range	O
from	O
telephone	O
transmitters	O
through	O
inexpensive	O
karaoke	O
microphones	B-Application
to	O
high-fidelity	O
recording	O
microphones	B-Application
.	O
</s>
<s>
The	O
inherent	O
suitability	O
of	O
this	O
technology	O
is	O
due	O
to	O
the	O
very	O
small	O
mass	O
that	O
must	O
be	O
moved	O
by	O
the	O
incident	O
sound	O
wave	O
,	O
unlike	O
other	O
microphone	B-Application
types	O
that	O
require	O
the	O
sound	O
wave	O
to	O
do	O
more	O
work	O
.	O
</s>
<s>
Condenser	O
microphones	B-Application
require	O
a	O
power	O
source	O
,	O
provided	O
either	O
via	O
microphone	B-Application
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>
Power	O
is	O
necessary	O
for	O
establishing	O
the	O
capacitor	O
plate	O
voltage	O
and	O
is	O
also	O
needed	O
to	O
power	O
the	O
microphone	B-Application
electronics	O
(	O
impedance	O
conversion	O
in	O
the	O
case	O
of	O
electret	O
and	O
DC-polarized	O
microphones	B-Application
,	O
demodulation	O
or	O
detection	O
in	O
the	O
case	O
of	O
RF/HF	O
microphones	B-Application
)	O
.	O
</s>
<s>
Condenser	O
microphones	B-Application
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>
It	O
is	O
also	O
possible	O
to	O
vary	O
the	O
pattern	O
continuously	O
with	O
some	O
microphones	B-Application
,	O
for	O
example	O
,	O
the	O
Røde	O
NT2000	O
or	O
CAD	O
M179	O
.	O
</s>
<s>
There	O
are	O
two	O
main	O
categories	O
of	O
condenser	O
microphones	B-Application
,	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	B-Application
,	O
and	O
radio	O
frequency	O
(	O
RF	O
)	O
or	O
high	O
frequency	O
(	O
HF	O
)	O
condenser	O
microphones	B-Application
.	O
</s>
<s>
With	O
a	O
DC-biased	O
condenser	O
microphone	B-Application
,	O
the	O
plates	O
are	O
biased	O
with	O
a	O
fixed	O
charge	O
(	O
Q	O
)	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>
In	O
most	O
cases	O
,	O
the	O
electronics	O
in	O
the	O
microphone	B-Application
itself	O
contribute	O
no	O
voltage	O
gain	O
as	O
the	O
voltage	O
differential	O
is	O
quite	O
significant	O
,	O
up	O
to	O
several	O
volts	O
for	O
high	O
sound	O
levels	O
.	O
</s>
<s>
RF	O
condenser	O
microphones	B-Application
use	O
a	O
comparatively	O
low	O
RF	O
voltage	O
,	O
generated	O
by	O
a	O
low-noise	O
oscillator	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>
The	O
RF	O
biasing	O
process	O
results	O
in	O
a	O
lower	O
electrical	O
impedance	O
capsule	O
,	O
a	O
useful	O
by-product	O
of	O
which	O
is	O
that	O
RF	O
condenser	O
microphones	B-Application
can	O
be	O
operated	O
in	O
damp	O
weather	O
conditions	O
that	O
could	O
create	O
problems	O
in	O
DC-biased	O
microphones	B-Application
with	O
contaminated	O
insulating	O
surfaces	O
.	O
</s>
<s>
The	O
Sennheiser	O
"	O
MKH	O
"	O
series	O
of	O
microphones	B-Application
use	O
the	O
RF	O
biasing	O
technique	O
.	O
</s>
<s>
An	O
electret	O
microphone	B-Application
is	O
a	O
type	O
of	O
condenser	O
microphone	B-Application
invented	O
by	O
Gerhard	O
Sessler	O
and	O
Jim	O
West	O
at	O
Bell	O
laboratories	O
in	O
1962	O
.	O
</s>
<s>
The	O
externally	O
applied	O
charge	O
used	O
for	O
a	O
conventional	O
condenser	O
microphone	B-Application
is	O
replaced	O
by	O
a	O
permanent	O
charge	O
in	O
an	O
electret	O
material	O
.	O
</s>
<s>
Due	O
to	O
their	O
good	O
performance	O
and	O
ease	O
of	O
manufacture	O
,	O
hence	O
low	O
cost	O
,	O
the	O
vast	O
majority	O
of	O
microphones	B-Application
made	O
today	O
are	O
electret	O
microphones	B-Application
;	O
a	O
semiconductor	O
manufacturer	O
estimates	O
annual	O
production	O
at	O
over	O
one	O
billion	O
units	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	B-Application
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	B-Application
,	O
nearly	O
all	O
cell-phone	O
,	O
computer	O
,	O
PDA	O
and	O
headset	O
microphones	B-Application
were	O
electret	O
types	O
.	O
</s>
<s>
Unlike	O
other	O
capacitor	O
microphones	B-Application
,	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	B-Application
designed	O
for	O
personal	B-Device
computers	I-Device
(	O
PCs	B-Device
)	O
,	O
sometimes	O
called	O
multimedia	O
microphones	B-Application
,	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>
Stereophonic	O
microphones	B-Application
use	O
the	O
same	O
connector	O
;	O
there	O
is	O
no	O
obvious	O
way	O
to	O
determine	O
which	O
standard	O
is	O
used	O
by	O
equipment	O
and	O
microphones	B-Application
.	O
</s>
<s>
Though	O
electret	O
microphones	B-Application
were	O
once	O
considered	O
low	O
quality	O
,	O
the	O
best	O
ones	O
can	O
now	O
rival	O
traditional	O
condenser	O
microphones	B-Application
in	O
every	O
respect	O
and	O
can	O
even	O
offer	O
the	O
long-term	O
stability	O
and	O
ultra-flat	O
response	O
needed	O
for	O
a	O
measurement	O
microphone	B-Application
.	O
</s>
<s>
Only	O
the	O
best	O
electret	O
microphones	B-Application
rival	O
good	O
DC-polarized	O
units	O
in	O
terms	O
of	O
noise	O
level	O
and	O
quality	O
;	O
electret	O
microphones	B-Application
lend	O
themselves	O
to	O
inexpensive	O
mass-production	O
,	O
while	O
inherently	O
expensive	O
non-electret	O
condenser	O
microphones	B-Application
are	O
made	O
to	O
higher	O
quality	O
.	O
</s>
<s>
A	O
valve	B-Algorithm
microphone	I-Algorithm
is	O
a	O
condenser	O
microphone	B-Application
that	O
uses	O
a	O
vacuum	O
tube	O
(	O
valve	O
)	O
amplifier	O
.	O
</s>
<s>
The	O
dynamic	O
microphone	B-Application
(	O
also	O
known	O
as	O
the	O
moving-coil	O
microphone	B-Application
)	O
works	O
via	O
electromagnetic	O
induction	O
.	O
</s>
<s>
Dynamic	O
microphones	B-Application
use	O
the	O
same	O
dynamic	O
principle	O
as	O
in	O
a	O
loudspeaker	O
,	O
only	O
reversed	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	B-Application
,	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>
For	O
this	O
reason	O
,	O
some	O
microphones	B-Application
utilize	O
multiple	O
membranes	O
for	O
the	O
different	O
parts	O
of	O
the	O
audio	O
spectrum	O
and	O
then	O
combine	O
the	O
resulting	O
signals	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>
The	O
ribbon	O
is	O
electrically	O
connected	O
to	O
the	O
microphone	B-Application
's	O
output	O
,	O
and	O
its	O
vibration	O
within	O
the	O
magnetic	O
field	O
generates	O
the	O
electrical	O
signal	O
.	O
</s>
<s>
Ribbon	B-Algorithm
microphones	I-Algorithm
are	O
similar	O
to	O
moving	O
coil	O
microphones	B-Application
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	B-Application
,	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>
The	O
carbon	O
microphone	B-Application
was	O
the	O
earliest	O
type	O
of	O
microphone	B-Application
.	O
</s>
<s>
The	O
carbon	O
button	O
microphone	B-Application
(	O
or	O
sometimes	O
just	O
a	O
button	O
microphone	B-Application
)	O
,	O
uses	O
a	O
capsule	O
or	O
button	O
containing	O
carbon	O
granules	O
pressed	O
between	O
two	O
metal	O
plates	O
like	O
the	O
Berliner	O
and	O
Edison	O
microphones	B-Application
.	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>
The	O
changes	O
in	O
resistance	O
cause	O
a	O
corresponding	O
change	O
in	O
the	O
current	O
flowing	O
through	O
the	O
microphone	B-Application
,	O
producing	O
the	O
electrical	O
signal	O
.	O
</s>
<s>
Carbon	O
microphones	B-Application
were	O
once	O
commonly	O
used	O
in	O
telephones	O
;	O
they	O
have	O
extremely	O
low-quality	O
sound	O
reproduction	O
and	O
a	O
very	O
limited	O
frequency	O
response	O
range	O
but	O
are	O
very	O
robust	O
devices	O
.	O
</s>
<s>
The	O
Boudet	O
microphone	B-Application
,	O
which	O
used	O
relatively	O
large	O
carbon	O
balls	O
,	O
was	O
similar	O
to	O
the	O
granule	O
carbon	O
button	O
microphones	B-Application
.	O
</s>
<s>
Unlike	O
other	O
microphone	B-Application
types	O
,	O
the	O
carbon	O
microphone	B-Application
can	O
also	O
be	O
used	O
as	O
a	O
type	O
of	O
amplifier	O
,	O
using	O
a	O
small	O
amount	O
of	O
sound	O
energy	O
to	O
control	O
a	O
larger	O
amount	O
of	O
electrical	O
energy	O
.	O
</s>
<s>
Carbon	O
microphones	B-Application
found	O
use	O
as	O
early	O
telephone	O
repeaters	O
,	O
making	O
long-distance	O
phone	O
calls	O
possible	O
in	O
the	O
era	O
before	O
vacuum	O
tubes	O
.	O
</s>
<s>
Called	O
a	O
Brown	O
's	O
relay	O
,	O
these	O
repeaters	O
worked	O
by	O
mechanically	O
coupling	O
a	O
magnetic	O
telephone	O
receiver	O
to	O
a	O
carbon	O
microphone	B-Application
:	O
the	O
faint	O
signal	O
from	O
the	O
receiver	O
was	O
transferred	O
to	O
the	O
microphone	B-Application
,	O
where	O
it	O
modulated	O
a	O
stronger	O
electric	O
current	O
,	O
producing	O
a	O
stronger	O
electrical	O
signal	O
to	O
send	O
down	O
the	O
line	O
.	O
</s>
<s>
One	O
illustration	O
of	O
this	O
amplifier	O
effect	O
was	O
the	O
oscillation	O
caused	O
by	O
feedback	O
,	O
resulting	O
in	O
an	O
audible	O
squeal	O
from	O
the	O
old	O
"	O
candlestick	O
"	O
telephone	O
if	O
its	O
earphone	O
was	O
placed	O
near	O
the	O
carbon	O
microphone	B-Application
.	O
</s>
<s>
A	O
crystal	O
microphone	B-Application
or	O
piezo	O
microphone	B-Application
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	B-Application
and	O
as	O
a	O
slimline	O
loudspeaker	O
component	O
.	O
</s>
<s>
Crystal	O
microphones	B-Application
were	O
once	O
commonly	O
supplied	O
with	O
vacuum	O
tube	O
(	O
valve	O
)	O
equipment	O
,	O
such	O
as	O
domestic	O
tape	O
recorders	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	B-Application
for	O
a	O
time	O
,	O
and	O
later	O
small	O
electret	O
condenser	O
devices	O
.	O
</s>
<s>
The	O
high	O
impedance	O
of	O
the	O
crystal	O
microphone	B-Application
made	O
it	O
very	O
susceptible	O
to	O
handling	O
noise	O
,	O
both	O
from	O
the	O
microphone	B-Application
itself	O
and	O
from	O
the	O
connecting	O
cable	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>
This	O
type	O
of	O
microphone	B-Application
is	O
different	O
from	O
magnetic	O
coil	O
pickups	O
commonly	O
visible	O
on	O
typical	O
electric	O
guitars	O
,	O
which	O
use	O
magnetic	O
induction	O
,	O
rather	O
than	O
mechanical	O
coupling	O
,	O
to	O
pick	O
up	O
vibration	O
.	O
</s>
<s>
A	O
fiber-optic	B-Architecture
microphone	B-Application
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	B-Application
.	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	B-Application
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	B-Application
.	O
</s>
<s>
Fiber-optic	B-Architecture
microphones	B-Application
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	B-Application
design	O
is	O
therefore	O
ideal	O
for	O
use	O
in	O
areas	O
where	O
conventional	O
microphones	B-Application
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	B-Application
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	B-Application
'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	B-Application
suitable	O
for	O
industrial	O
and	O
surveillance	O
acoustic	O
monitoring	O
.	O
</s>
<s>
Fiber-optic	B-Architecture
microphones	B-Application
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>
Laser	O
microphones	B-Application
are	O
often	O
portrayed	O
in	O
movies	O
as	O
spy	O
gadgets	O
because	O
they	O
can	O
be	O
used	O
to	O
pick	O
up	O
sound	O
at	O
a	O
distance	O
from	O
the	O
microphone	B-Application
equipment	O
.	O
</s>
<s>
A	O
new	O
type	O
of	O
laser	O
microphone	B-Application
is	O
a	O
device	O
that	O
uses	O
a	O
laser	O
beam	O
and	O
smoke	O
or	O
vapor	O
to	O
detect	O
sound	O
vibrations	O
in	O
free	O
air	O
.	O
</s>
<s>
On	O
August	O
25	O
,	O
2009	O
,	O
U.S.	O
patent	O
7,580,533	O
issued	O
for	O
a	O
Particulate	O
Flow	O
Detection	O
Microphone	B-Application
based	O
on	O
a	O
laser-photocell	O
pair	O
with	O
a	O
moving	O
stream	O
of	O
smoke	O
or	O
vapor	O
in	O
the	O
laser	O
beam	O
's	O
path	O
.	O
</s>
<s>
Early	O
microphones	B-Application
did	O
not	O
produce	O
intelligible	O
speech	O
,	O
until	O
Alexander	O
Graham	O
Bell	O
made	O
improvements	O
including	O
a	O
variable-resistance	O
microphone/transmitter	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>
Other	O
minor	O
variations	O
and	O
improvements	O
were	O
made	O
to	O
the	O
liquid	O
microphone	B-Application
by	O
Majoranna	O
,	O
Chambers	O
,	O
Vanni	O
,	O
Sykes	O
,	O
and	O
Elisha	O
Gray	O
,	O
and	O
one	O
version	O
was	O
patented	O
by	O
Reginald	O
Fessenden	O
in	O
1903	O
.	O
</s>
<s>
These	O
were	O
the	O
first	O
working	O
microphones	B-Application
,	O
but	O
they	O
were	O
not	O
practical	O
for	O
commercial	O
application	O
.	O
</s>
<s>
The	O
famous	O
first	O
phone	O
conversation	O
between	O
Bell	O
and	O
Watson	O
took	O
place	O
using	O
a	O
liquid	O
microphone	B-Application
.	O
</s>
<s>
The	O
MEMS	B-Architecture
(	O
microelectromechanical	B-Architecture
systems	I-Architecture
)	O
microphone	B-Application
is	O
also	O
called	O
a	O
microphone	B-Application
chip	O
or	O
silicon	O
microphone	B-Application
.	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	B-Application
are	O
variants	O
of	O
the	O
condenser	O
microphone	B-Application
design	O
.	O
</s>
<s>
Digital	O
MEMS	B-Architecture
microphones	B-Application
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	B-Application
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	B-Application
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	B-Application
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>
In	O
a	O
plasma	O
microphone	B-Application
a	O
plasma	O
arc	O
of	O
ionized	O
gas	O
is	O
used	O
.	O
</s>
<s>
This	O
is	O
a	O
very	O
rare	O
form	O
of	O
microphone	B-Application
.	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	B-Application
.	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	B-Application
(	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	B-Application
.	O
</s>
<s>
Reciprocity	O
applies	O
,	O
so	O
the	O
resulting	O
microphone	B-Application
has	O
the	O
same	O
impairments	O
as	O
a	O
single-driver	O
loudspeaker	O
:	O
limited	O
low	O
-	O
and	O
high-end	O
frequency	O
response	O
,	O
poorly	O
controlled	O
directivity	O
,	O
and	O
low	O
sensitivity	O
.	O
</s>
<s>
In	O
practical	O
use	O
,	O
speakers	O
are	O
sometimes	O
used	O
as	O
microphones	B-Application
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	B-Application
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	B-Application
.	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>
The	O
inner	O
elements	O
of	O
a	O
microphone	B-Application
are	O
the	O
primary	O
source	O
of	O
differences	O
in	O
directivity	O
.	O
</s>
<s>
A	O
pressure	O
microphone	B-Application
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	B-Application
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>
Other	O
elements	O
such	O
as	O
the	O
external	O
shape	O
of	O
the	O
microphone	B-Application
and	O
external	O
devices	O
such	O
as	O
interference	O
tubes	O
can	O
also	O
alter	O
a	O
microphone	B-Application
's	O
directional	O
response	O
.	O
</s>
<s>
A	O
pure	O
pressure-gradient	O
microphone	B-Application
is	O
equally	O
sensitive	O
to	O
sounds	O
arriving	O
from	O
front	O
or	O
back	O
but	O
insensitive	O
to	O
sounds	O
arriving	O
from	O
the	O
side	O
because	O
sound	O
arriving	O
at	O
the	O
front	O
and	O
back	O
at	O
the	O
same	O
time	O
creates	O
no	O
gradient	O
between	O
the	O
two	O
.	O
</s>
<s>
The	O
characteristic	O
directional	O
pattern	O
of	O
a	O
pure	O
pressure-gradient	O
microphone	B-Application
is	O
like	O
a	O
figure-8	O
.	O
</s>
<s>
A	O
microphone	B-Application
's	O
directionality	O
or	O
polar	O
pattern	O
indicates	O
how	O
sensitive	O
it	O
is	O
to	O
sounds	O
arriving	O
at	O
different	O
angles	O
about	O
its	O
central	O
axis	O
.	O
</s>
<s>
The	O
polar	O
patterns	O
illustrated	O
above	O
represent	O
the	O
locus	O
of	O
points	O
that	O
produce	O
the	O
same	O
signal	O
level	O
output	O
in	O
the	O
microphone	B-Application
if	O
a	O
given	O
sound	O
pressure	O
level	O
(	O
SPL	O
)	O
is	O
generated	O
from	O
that	O
point	O
.	O
</s>
<s>
How	O
the	O
physical	O
body	O
of	O
the	O
microphone	B-Application
is	O
oriented	O
relative	O
to	O
the	O
diagrams	O
depends	O
on	O
the	O
microphone	B-Application
design	O
.	O
</s>
<s>
For	O
large-membrane	O
microphones	B-Application
such	O
as	O
in	O
the	O
Oktava	O
(	O
pictured	O
above	O
)	O
,	O
the	O
upward	O
direction	O
in	O
the	O
polar	O
diagram	O
is	O
usually	O
perpendicular	O
to	O
the	O
microphone	B-Application
body	O
,	O
commonly	O
known	O
as	O
"	O
side	O
fire	O
"	O
or	O
"	O
side	O
address	O
"	O
.	O
</s>
<s>
For	O
small	O
diaphragm	B-Device
microphones	B-Application
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	B-Application
commonly	O
known	O
as	O
"	O
end	O
fire	O
"	O
or	O
"	O
top/end	O
address	O
"	O
.	O
</s>
<s>
Some	O
microphone	B-Application
designs	O
combine	O
several	O
principles	O
in	O
creating	O
the	O
desired	O
polar	O
pattern	O
.	O
</s>
<s>
An	O
omnidirectional	O
(	O
or	O
nondirectional	O
)	O
microphone	B-Application
's	O
response	O
is	O
generally	O
considered	O
to	O
be	O
a	O
perfect	O
sphere	O
in	O
three	O
dimensions	O
.	O
</s>
<s>
As	O
with	O
directional	O
microphones	B-Application
,	O
the	O
polar	O
pattern	O
for	O
an	O
"	O
omnidirectional	O
"	O
microphone	B-Application
is	O
a	O
function	O
of	O
frequency	O
.	O
</s>
<s>
The	O
body	O
of	O
the	O
microphone	B-Application
is	O
not	O
infinitely	O
small	O
and	O
,	O
as	O
a	O
consequence	O
,	O
it	O
tends	O
to	O
get	O
in	O
its	O
own	O
way	O
with	O
respect	O
to	O
sounds	O
arriving	O
from	O
the	O
rear	O
,	O
causing	O
a	O
slight	O
flattening	O
of	O
the	O
polar	O
response	O
.	O
</s>
<s>
This	O
flattening	O
increases	O
as	O
the	O
diameter	O
of	O
the	O
microphone	B-Application
(	O
assuming	O
it	O
's	O
cylindrical	O
)	O
reaches	O
the	O
wavelength	O
of	O
the	O
frequency	O
in	O
question	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
smallest	O
diameter	O
microphone	B-Application
gives	O
the	O
best	O
omnidirectional	O
characteristics	O
at	O
high	O
frequencies	O
.	O
</s>
<s>
The	O
smallest	O
measuring	O
microphones	B-Application
are	O
often	O
1/4	O
"	O
(	O
6mm	O
)	O
in	O
diameter	O
,	O
which	O
practically	O
eliminates	O
directionality	O
even	O
up	O
to	O
the	O
highest	O
frequencies	O
.	O
</s>
<s>
Omnidirectional	O
microphones	B-Application
,	O
unlike	O
cardioids	O
,	O
do	O
not	O
employ	O
resonant	O
cavities	O
as	O
delays	O
,	O
and	O
so	O
can	O
be	O
considered	O
the	O
"	O
purest	O
"	O
microphones	B-Application
in	O
terms	O
of	O
low	O
coloration	O
;	O
they	O
add	O
very	O
little	O
to	O
the	O
original	O
sound	O
.	O
</s>
<s>
Pressure-sensitive	O
microphones	B-Application
also	O
respond	O
much	O
less	O
to	O
wind	O
noise	O
and	O
plosives	O
than	O
directional	O
(	O
velocity	O
sensitive	O
)	O
microphones	B-Application
.	O
</s>
<s>
An	O
example	O
of	O
a	O
nondirectional	O
microphone	B-Application
is	O
the	O
round	O
black	O
eight	O
ball	O
.	O
</s>
<s>
A	O
unidirectional	O
microphone	B-Application
is	O
primarily	O
sensitive	O
to	O
sounds	O
from	O
only	O
one	O
direction	O
.	O
</s>
<s>
The	O
microphone	B-Application
faces	O
upwards	O
in	O
each	O
diagram	O
.	O
</s>
<s>
The	O
most	O
common	O
unidirectional	O
microphone	B-Application
is	O
a	O
cardioid	O
microphone	B-Application
,	O
so	O
named	O
because	O
the	O
sensitivity	O
pattern	O
is	O
"	O
heart-shaped	O
"	O
(	O
i.e.	O
</s>
<s>
The	O
cardioid	O
family	O
of	O
microphones	B-Application
are	O
commonly	O
used	O
as	O
vocal	O
or	O
speech	O
microphones	B-Application
since	O
they	O
are	O
good	O
at	O
rejecting	O
sounds	O
from	O
other	O
directions	O
.	O
</s>
<s>
In	O
three	O
dimensions	O
,	O
the	O
cardioid	O
is	O
shaped	O
like	O
an	O
apple	O
centered	O
around	O
the	O
microphone	B-Application
,	O
which	O
is	O
the	O
"	O
stem	O
"	O
of	O
the	O
apple	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	B-Application
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	B-Application
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>
The	O
cardioid	O
is	O
effectively	O
a	O
superposition	O
of	O
an	O
omnidirectional	O
(	O
pressure	O
)	O
and	O
a	O
figure-8	O
(	O
pressure	O
gradient	O
)	O
microphone	B-Application
;	O
for	O
sound	O
waves	O
coming	O
from	O
the	O
back	O
,	O
the	O
negative	O
signal	O
from	O
the	O
figure-8	O
cancels	O
the	O
positive	O
signal	O
from	O
the	O
omnidirectional	O
element	O
,	O
whereas	O
,	O
for	O
sound	O
waves	O
coming	O
from	O
the	O
front	O
,	O
the	O
two	O
add	O
to	O
each	O
other	O
.	O
</s>
<s>
However	O
,	O
in	O
low	O
frequencies	O
a	O
cardioid	O
microphone	B-Application
behaves	O
as	O
an	O
omnidirectional	O
microphone	B-Application
.	O
</s>
<s>
A	O
hyper-cardioid	O
microphone	B-Application
is	O
similar	O
to	O
cardioid	O
,	O
but	O
with	O
a	O
slightly	O
larger	O
figure-8	O
contribution	O
,	O
leading	O
to	O
a	O
tighter	O
area	O
of	O
front	O
sensitivity	O
and	O
a	O
smaller	O
lobe	O
of	O
rear	O
sensitivity	O
.	O
</s>
<s>
A	O
super-cardioid	O
microphone	B-Application
is	O
similar	O
to	O
a	O
hyper-cardioid	O
,	O
except	O
there	O
is	O
more	O
front	O
pickup	O
and	O
less	O
rear	O
pickup	O
.	O
</s>
<s>
The	O
sub-cardioid	O
microphone	B-Application
has	O
no	O
null	O
points	O
.	O
</s>
<s>
Three	O
such	O
cardioid	O
microphones/hydrophones	O
could	O
be	O
orthogonally	O
oriented	O
as	O
a	O
collocated	O
triad	O
to	O
improve	O
the	O
gain	O
and	O
also	O
create	O
a	O
steerable	O
beam	O
pattern	O
.	O
</s>
<s>
"	O
Figure	O
8	O
"	O
or	O
bi-directional	O
microphones	B-Application
receive	O
sound	O
equally	O
from	O
both	O
the	O
front	O
and	O
back	O
of	O
the	O
element	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	B-Application
are	O
scalar	O
transducers	B-Algorithm
responding	O
to	O
pressure	O
from	O
any	O
direction	O
,	O
bi-directional	O
microphones	B-Application
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>
Shotgun	O
microphones	B-Application
are	O
the	O
most	O
highly	O
directional	O
of	O
simple	O
first-order	O
unidirectional	O
types	O
.	O
</s>
<s>
Due	O
to	O
the	O
narrowness	O
of	O
their	O
forward	O
sensitivity	O
,	O
shotgun	O
microphones	B-Application
are	O
commonly	O
used	O
on	O
television	O
and	O
film	O
sets	O
,	O
in	O
stadiums	O
,	O
and	O
for	O
field	O
recording	O
of	O
wildlife	O
.	O
</s>
<s>
Several	O
approaches	O
have	O
been	O
developed	O
for	O
effectively	O
using	O
a	O
microphone	B-Application
in	O
less-than-ideal	O
acoustic	O
spaces	O
,	O
which	O
often	O
suffer	O
from	O
excessive	O
reflections	O
from	O
one	O
or	O
more	O
of	O
the	O
surfaces	O
(	O
boundaries	O
)	O
that	O
make	O
up	O
the	O
space	O
.	O
</s>
<s>
If	O
the	O
microphone	B-Application
is	O
placed	O
in	O
,	O
or	O
very	O
close	O
to	O
,	O
one	O
of	O
these	O
boundaries	O
,	O
the	O
reflections	O
from	O
that	O
surface	O
have	O
the	O
same	O
timing	O
as	O
the	O
direct	O
sound	O
,	O
thus	O
giving	O
the	O
microphone	B-Application
a	O
hemispherical	O
polar	O
pattern	O
and	O
improved	O
intelligibility	O
.	O
</s>
<s>
Initially	O
,	O
this	O
was	O
done	O
by	O
placing	O
an	O
ordinary	O
microphone	B-Application
adjacent	O
to	O
the	O
surface	O
,	O
sometimes	O
in	O
a	O
block	O
of	O
acoustically	O
transparent	O
foam	O
.	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	B-Application
"	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	B-Application
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>
These	O
small	O
microphones	B-Application
are	O
worn	O
on	O
the	O
body	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	B-Application
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
portable	O
version	O
of	O
this	O
microphone	B-Application
has	O
recently	O
been	O
developed	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
parabolic	O
microphone	B-Application
uses	O
a	O
parabolic	O
reflector	O
to	O
collect	O
and	O
focus	O
sound	O
waves	O
onto	O
a	O
microphone	B-Application
receiver	O
,	O
in	O
much	O
the	O
same	O
way	O
that	O
a	O
parabolic	O
antenna	O
(	O
e.g.	O
</s>
<s>
Typical	O
uses	O
of	O
this	O
microphone	B-Application
,	O
which	O
has	O
unusually	O
focused	O
front	O
sensitivity	O
and	O
can	O
pick	O
up	O
sounds	O
from	O
many	O
meters	O
away	O
,	O
include	O
nature	O
recording	O
,	O
outdoor	O
sporting	O
events	O
,	O
eavesdropping	O
,	O
law	O
enforcement	O
,	O
and	O
even	O
espionage	O
.	O
</s>
<s>
Parabolic	O
microphones	B-Application
are	O
not	O
typically	O
used	O
for	O
standard	O
recording	O
applications	O
,	O
because	O
they	O
tend	O
to	O
have	O
a	O
poor	O
low-frequency	O
response	O
as	O
a	O
side	O
effect	O
of	O
their	O
design	O
.	O
</s>
<s>
A	O
stereo	O
microphone	B-Application
integrates	O
two	O
microphones	B-Application
in	O
one	O
unit	O
to	O
produce	O
a	O
stereophonic	O
signal	O
.	O
</s>
<s>
A	O
stereo	O
microphone	B-Application
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	B-Application
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>
Some	O
such	O
microphones	B-Application
have	O
an	O
adjustable	O
angle	O
of	O
coverage	O
between	O
the	O
two	O
channels	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>
One	O
such	O
use	O
is	O
in	O
aircraft	O
cockpits	O
where	O
they	O
are	O
normally	O
installed	O
as	O
boom	O
microphones	B-Application
on	O
headsets	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	B-Application
,	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>
Various	O
standard	O
techniques	O
are	O
used	O
with	O
microphones	B-Application
used	O
in	O
sound	O
reinforcement	O
at	O
live	O
performances	O
,	O
or	O
for	O
recording	O
in	O
a	O
studio	O
or	O
on	O
a	O
motion	O
picture	O
set	O
.	O
</s>
<s>
By	O
suitable	O
arrangement	O
of	O
one	O
or	O
more	O
microphones	B-Application
,	O
desirable	O
features	O
of	O
the	O
sound	O
to	O
be	O
collected	O
can	O
be	O
kept	O
,	O
while	O
rejecting	O
unwanted	O
sounds	O
.	O
</s>
<s>
Microphones	B-Application
containing	O
active	O
circuitry	O
,	O
such	O
as	O
most	O
condenser	O
microphones	B-Application
,	O
require	O
power	O
to	O
operate	O
the	O
active	O
components	O
.	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	B-Application
.	O
</s>
<s>
In	O
consumer	O
electronics	O
such	O
as	O
DSLRs	O
and	O
camcorders	O
,	O
"	O
plug-in	O
power	O
"	O
is	O
more	O
common	O
,	O
for	O
microphones	B-Application
using	O
a	O
3.5mm	O
phone	O
plug	O
connector	O
.	O
</s>
<s>
The	O
most	O
common	O
connectors	O
used	O
by	O
microphones	B-Application
are	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	B-Application
,	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>
Harmonica	O
microphones	B-Application
commonly	O
use	O
a	O
high	O
impedance	O
inch	O
TS	O
connection	O
to	O
be	O
run	O
through	O
guitar	O
amplifiers	O
.	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	B-Application
.	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	B-Application
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
microphones	B-Application
use	O
other	O
connectors	O
,	O
such	O
as	O
a	O
5-pin	O
XLR	O
,	O
or	O
mini	O
XLR	O
for	O
connection	O
to	O
portable	O
equipment	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	B-Application
to	O
the	O
news	O
reporter	O
's	O
suit	O
lapel	O
)	O
microphones	B-Application
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	B-Application
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>
When	O
choosing	O
a	O
pre-amplifier	O
for	O
a	O
certain	O
microphone	B-Application
,	O
the	O
microphone	B-Application
's	O
impedance	O
must	O
be	O
known	O
.	O
</s>
<s>
When	O
not	O
concerned	O
with	O
power	O
transfer	O
,	O
signals	O
are	O
generally	O
transferred	O
as	O
varying	O
voltages	O
and	O
this	O
is	O
also	O
the	O
case	O
for	O
microphones	B-Application
.	O
</s>
<s>
In	O
this	O
configuration	O
the	O
output	O
impedance	O
of	O
the	O
microphone	B-Application
should	O
be	O
negligible	O
in	O
comparison	O
with	O
the	O
input	O
impedance	O
of	O
the	O
pre-amplifier	O
(	O
in	O
practice	O
a	O
pre-amp	O
impedance	O
at	O
least	O
10	O
times	O
greater	O
than	O
the	O
microphone	B-Application
impedance	O
is	O
recommended	O
)	O
.	O
</s>
<s>
Certain	O
ribbon	O
and	O
dynamic	O
microphones	B-Application
however	O
are	O
exceptions	O
,	O
due	O
to	O
the	O
designers	O
 '	O
assumption	O
of	O
a	O
certain	O
load	O
impedance	O
being	O
part	O
of	O
the	O
internal	O
electro-acoustical	O
damping	O
circuit	O
of	O
the	O
microphone	B-Application
.	O
</s>
<s>
Different	O
microphones	B-Application
can	O
have	O
vastly	O
different	O
impedances	O
and	O
this	O
depends	O
on	O
the	O
design	O
.	O
</s>
<s>
In	O
passive	O
microphones	B-Application
,	O
this	O
value	O
relates	O
closely	O
to	O
the	O
impedance	O
of	O
the	O
coil	O
(	O
or	O
similar	O
mechanism	O
)	O
.	O
</s>
<s>
In	O
active	O
microphones	B-Application
,	O
this	O
value	O
describes	O
the	O
output	O
impedance	O
of	O
its	O
internal	O
amplifier	O
circuitry	O
.	O
</s>
<s>
Owing	O
to	O
their	O
built-in	O
amplifier	O
,	O
condenser	O
microphones	B-Application
typically	O
have	O
an	O
output	O
impedance	O
between	O
50	O
and	O
200Ω	O
.	O
</s>
<s>
If	O
a	O
microphone	B-Application
is	O
made	O
in	O
high	O
and	O
low	O
impedance	O
versions	O
,	O
the	O
high	O
impedance	O
version	O
has	O
a	O
higher	O
output	O
voltage	O
for	O
a	O
given	O
sound	O
pressure	O
input	O
,	O
and	O
is	O
suitable	O
for	O
use	O
with	O
vacuum-tube	O
guitar	O
amplifiers	O
,	O
for	O
instance	O
,	O
which	O
have	O
a	O
high	O
input	O
impedance	O
and	O
require	O
a	O
relatively	O
high	O
signal	O
input	O
voltage	O
to	O
overcome	O
the	O
tubes	O
 '	O
inherent	O
noise	O
.	O
</s>
<s>
Most	O
professional	O
microphones	B-Application
are	O
low	O
impedance	O
,	O
about	O
200Ω	O
or	O
lower	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	B-Application
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	B-Application
and	O
a	O
high	O
impedance	O
input	O
.	O
</s>
<s>
Low-impedance	O
microphones	B-Application
are	O
generally	O
preferred	O
over	O
high	O
impedance	O
for	O
the	O
following	O
reason	O
:	O
using	O
a	O
high-impedance	O
microphone	B-Application
with	O
a	O
long	O
cable	O
results	O
in	O
high-frequency	O
signal	O
loss	O
due	O
to	O
cable	O
capacitance	O
,	O
which	O
forms	O
a	O
low-pass	O
filter	O
with	O
the	O
microphone	B-Application
output	O
impedance	O
.	O
</s>
<s>
The	O
AES42	O
standard	O
,	O
published	O
by	O
the	O
Audio	O
Engineering	O
Society	O
,	O
defines	O
a	O
digital	O
interface	O
for	O
microphones	B-Application
.	O
</s>
<s>
Microphones	B-Application
conforming	O
to	O
this	O
standard	O
directly	O
output	O
a	O
digital	O
audio	O
stream	O
through	O
an	O
XLR	O
or	O
XLD	O
male	O
connector	O
,	O
rather	O
than	O
producing	O
an	O
analog	O
output	O
.	O
</s>
<s>
Digital	O
microphones	B-Application
may	O
be	O
used	O
either	O
with	O
new	O
equipment	O
with	O
appropriate	O
input	O
connections	O
that	O
conform	O
to	O
the	O
AES42	O
standard	O
,	O
or	O
else	O
via	O
a	O
suitable	O
interface	O
box	O
.	O
</s>
<s>
Studio-quality	O
microphones	B-Application
that	O
operate	O
in	O
accordance	O
with	O
the	O
AES42	O
standard	O
are	O
now	O
available	O
from	O
a	O
number	O
of	O
microphone	B-Application
manufacturers	O
.	O
</s>
<s>
Because	O
of	O
differences	O
in	O
their	O
construction	O
,	O
microphones	B-Application
have	O
their	O
own	O
characteristic	O
responses	O
to	O
sound	O
.	O
</s>
<s>
In	O
addition	O
,	O
microphones	B-Application
are	O
not	O
uniformly	O
sensitive	O
to	O
sound	O
pressure	O
and	O
can	O
accept	O
differing	O
levels	O
without	O
distorting	O
.	O
</s>
<s>
Although	O
for	O
scientific	O
applications	O
microphones	B-Application
with	O
a	O
more	O
uniform	O
response	O
are	O
desirable	O
,	O
this	O
is	O
often	O
not	O
the	O
case	O
for	O
music	O
recording	O
,	O
as	O
the	O
non-uniform	O
response	O
of	O
a	O
microphone	B-Application
can	O
produce	O
a	O
desirable	O
coloration	O
of	O
the	O
sound	O
.	O
</s>
<s>
There	O
is	O
an	O
international	O
standard	O
for	O
microphone	B-Application
specifications	O
,	O
but	O
few	O
manufacturers	O
adhere	O
to	O
it	O
.	O
</s>
<s>
The	O
Microphone	B-Application
Data	O
Website	O
has	O
collated	O
the	O
technical	O
specifications	O
complete	O
with	O
pictures	O
,	O
response	O
curves	O
and	O
technical	O
data	O
from	O
the	O
microphone	B-Application
manufacturers	O
for	O
every	O
currently	O
listed	O
microphone	B-Application
,	O
and	O
even	O
a	O
few	O
obsolete	O
models	O
,	O
and	O
shows	O
the	O
data	O
for	O
them	O
all	O
in	O
one	O
common	O
format	O
for	O
ease	O
of	O
comparison	O
..	O
</s>
<s>
A	O
frequency	O
response	O
diagram	O
plots	O
the	O
microphone	B-Application
sensitivity	O
in	O
decibels	O
over	O
a	O
range	O
of	O
frequencies	O
(	O
typically	O
20Hz	O
to	O
20kHz	O
)	O
,	O
generally	O
for	O
perfectly	O
on-axis	O
sound	O
(	O
sound	O
arriving	O
at	O
0°	O
to	O
the	O
capsule	O
)	O
.	O
</s>
<s>
Directional	O
microphones	B-Application
 '	O
frequency	O
response	O
varies	O
greatly	O
with	O
distance	O
from	O
the	O
sound	O
source	O
,	O
and	O
with	O
the	O
geometry	O
of	O
the	O
sound	O
source	O
.	O
</s>
<s>
Close	O
talking	O
microphones	B-Application
may	O
be	O
measured	O
with	O
different	O
sound	O
sources	O
and	O
distances	O
,	O
but	O
there	O
is	O
no	O
standard	O
and	O
therefore	O
no	O
way	O
to	O
compare	O
data	O
from	O
different	O
models	O
unless	O
the	O
measurement	O
technique	O
is	O
described	O
.	O
</s>
<s>
The	O
self-noise	O
or	O
equivalent	O
input	O
noise	O
level	O
is	O
the	O
sound	O
level	O
that	O
creates	O
the	O
same	O
output	O
voltage	O
as	O
the	O
microphone	B-Application
does	O
in	O
the	O
absence	O
of	O
sound	O
.	O
</s>
<s>
This	O
represents	O
the	O
lowest	O
point	O
of	O
the	O
microphone	B-Application
's	O
dynamic	O
range	O
,	O
and	O
is	O
particularly	O
important	O
should	O
you	O
wish	O
to	O
record	O
sounds	O
that	O
are	O
quiet	O
.	O
</s>
<s>
Some	O
microphone	B-Application
manufacturers	O
state	O
the	O
noise	O
level	O
using	O
ITU-R	O
468	O
noise	O
weighting	O
,	O
which	O
more	O
accurately	O
represents	O
the	O
way	O
we	O
hear	O
noise	O
,	O
but	O
gives	O
a	O
figure	O
some	O
11	O
–	O
14dB	O
higher	O
.	O
</s>
<s>
A	O
quiet	O
microphone	B-Application
typically	O
measures	O
20dBA	O
SPL	O
or	O
32dB	O
SPL	O
468-weighted	O
.	O
</s>
<s>
Very	O
quiet	O
microphones	B-Application
have	O
existed	O
for	O
years	O
for	O
special	O
applications	O
,	O
such	O
the	O
Brüel	O
&	O
Kjaer	O
4179	O
,	O
with	O
a	O
noise	O
level	O
around	O
0dB	O
SPL	O
.	O
</s>
<s>
Recently	O
some	O
microphones	B-Application
with	O
low	O
noise	O
specifications	O
have	O
been	O
introduced	O
in	O
the	O
studio/entertainment	O
market	O
,	O
such	O
as	O
models	O
from	O
Neumann	O
and	O
Røde	O
that	O
advertise	O
noise	O
levels	O
between	O
5	O
–	O
7dBA	O
.	O
</s>
<s>
The	O
maximum	O
SPL	O
the	O
microphone	B-Application
can	O
accept	O
is	O
measured	O
for	O
particular	O
values	O
of	O
total	O
harmonic	O
distortion	O
(	O
THD	O
)	O
,	O
typically	O
0.5	O
%	O
.	O
</s>
<s>
This	O
amount	O
of	O
distortion	O
is	O
generally	O
inaudible	O
,	O
so	O
one	O
can	O
safely	O
use	O
the	O
microphone	B-Application
at	O
this	O
SPL	O
without	O
harming	O
the	O
recording	O
.	O
</s>
<s>
The	O
higher	O
the	O
value	O
,	O
the	O
better	O
,	O
although	O
microphones	B-Application
with	O
a	O
very	O
high	O
maximum	O
SPL	O
also	O
have	O
a	O
higher	O
self-noise	O
.	O
</s>
<s>
For	O
some	O
microphones	B-Application
,	O
the	O
clipping	O
level	O
may	O
be	O
much	O
higher	O
than	O
the	O
max	O
SPL	O
.	O
</s>
<s>
The	O
dynamic	O
range	O
of	O
a	O
microphone	B-Application
is	O
the	O
difference	O
in	O
SPL	O
between	O
the	O
noise	O
floor	O
and	O
the	O
maximum	O
SPL	O
.	O
</s>
<s>
Sensitivity	O
indicates	O
how	O
well	O
the	O
microphone	B-Application
converts	O
acoustic	O
pressure	O
to	O
an	O
output	O
voltage	O
.	O
</s>
<s>
A	O
high	O
sensitivity	O
microphone	B-Application
creates	O
more	O
voltage	O
and	O
so	O
needs	O
less	O
amplification	O
at	O
the	O
mixer	O
or	O
recording	O
device	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	B-Application
'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>
Some	O
microphones	B-Application
are	O
intended	O
for	O
testing	O
speakers	O
,	O
measuring	O
noise	O
levels	O
and	O
otherwise	O
quantifying	O
an	O
acoustic	O
experience	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>
The	O
quality	O
of	O
measurement	O
microphones	B-Application
is	O
often	O
referred	O
to	O
using	O
the	O
designations	O
"	O
Class	O
1	O
,	O
"	O
"	O
Type	O
2	O
,	O
"	O
etc.	O
,	O
which	O
are	O
references	O
not	O
to	O
microphone	B-Application
specifications	O
but	O
to	O
sound	O
level	O
meters	O
.	O
</s>
<s>
A	O
more	O
comprehensive	O
standard	O
for	O
the	O
description	O
of	O
measurement	O
microphone	B-Application
performance	O
was	O
recently	O
adopted	O
.	O
</s>
<s>
Measurement	O
microphones	B-Application
are	O
generally	O
scalar	O
sensors	O
of	O
pressure	O
;	O
they	O
exhibit	O
an	O
omnidirectional	O
response	O
,	O
limited	O
only	O
by	O
the	O
scattering	O
profile	O
of	O
their	O
physical	O
dimensions	O
.	O
</s>
<s>
Sound	O
intensity	O
or	O
sound	O
power	O
measurements	O
require	O
pressure-gradient	O
measurements	O
,	O
which	O
are	O
typically	O
made	O
using	O
arrays	O
of	O
at	O
least	O
two	O
microphones	B-Application
,	O
or	O
with	O
hot-wire	O
anemometers	O
.	O
</s>
<s>
To	O
take	O
a	O
scientific	O
measurement	O
with	O
a	O
microphone	B-Application
,	O
its	O
precise	O
sensitivity	O
must	O
be	O
known	O
(	O
in	O
volts	O
per	O
pascal	O
)	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	B-Application
.	O
</s>
<s>
This	O
service	O
is	O
offered	O
by	O
some	O
microphone	B-Application
manufacturers	O
and	O
by	O
independent	O
certified	O
testing	O
labs	O
.	O
</s>
<s>
All	O
microphone	B-Application
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	B-Application
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	B-Application
using	O
comparison	O
calibration	B-General_Concept
techniques	O
.	O
</s>
<s>
Depending	O
on	O
the	O
application	O
,	O
measurement	O
microphones	B-Application
must	O
be	O
tested	O
periodically	O
(	O
every	O
year	O
or	O
several	O
months	O
,	O
typically	O
)	O
and	O
after	O
any	O
potentially	O
damaging	O
event	O
,	O
such	O
as	O
being	O
dropped	O
(	O
most	O
such	O
microphones	B-Application
come	O
in	O
foam-padded	O
cases	O
to	O
reduce	O
this	O
risk	O
)	O
or	O
exposed	O
to	O
sounds	O
beyond	O
the	O
acceptable	O
level	O
.	O
</s>
<s>
A	O
microphone	B-Application
array	O
is	O
any	O
number	O
of	O
microphones	B-Application
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	B-Application
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>
<s>
Windscreens	O
(	O
or	O
windshields	O
–	O
the	O
terms	O
are	O
interchangeable	O
)	O
provide	O
a	O
method	O
of	O
reducing	O
the	O
effect	O
of	O
wind	O
on	O
microphones	B-Application
.	O
</s>
<s>
While	O
pop-screens	O
give	O
protection	O
from	O
unidirectional	O
blasts	O
,	O
foam	O
"	O
hats	O
"	O
shield	O
wind	O
into	O
the	O
grille	O
from	O
all	O
directions	O
,	O
and	O
blimps	O
/	O
zeppelins	O
/	O
baskets	O
entirely	O
enclose	O
the	O
microphone	B-Application
and	O
protect	O
its	O
body	O
as	O
well	O
.	O
</s>
<s>
The	O
latter	O
is	O
important	O
because	O
,	O
given	O
the	O
extreme	O
low-frequency	O
content	O
of	O
wind	O
noise	O
,	O
vibration	O
induced	O
in	O
the	O
housing	O
of	O
the	O
microphone	B-Application
can	O
contribute	O
substantially	O
to	O
the	O
noise	O
output	O
.	O
</s>
<s>
Since	O
all	O
wind	O
noise	O
is	O
generated	O
at	O
the	O
first	O
surface	O
the	O
air	O
hits	O
,	O
the	O
greater	O
the	O
spacing	O
between	O
the	O
shield	O
periphery	O
and	O
microphone	B-Application
capsule	O
,	O
the	O
greater	O
the	O
noise	O
attenuation	O
.	O
</s>
<s>
With	O
full	O
basket	O
windshields	O
there	O
is	O
an	O
additional	O
pressure	O
chamber	O
effect	O
,	O
first	O
explained	O
by	O
Joerg	O
Wuttke	O
,	O
which	O
,	O
for	O
two-port	O
(	O
pressure	O
gradient	O
)	O
microphones	B-Application
,	O
allows	O
the	O
shield/microphone	O
combination	O
to	O
act	O
as	O
a	O
high-pass	O
acoustic	O
filter	O
.	O
</s>
<s>
In	O
the	O
studio	O
and	O
on	O
stage	O
,	O
pop-screens	O
and	O
foam	O
shields	O
can	O
be	O
useful	O
for	O
reasons	O
of	O
hygiene	O
and	O
protecting	O
microphones	B-Application
from	O
spittle	O
and	O
sweat	O
.	O
</s>
<s>
On	O
location	O
,	O
the	O
basket	O
shield	O
can	O
contain	O
a	O
suspension	O
system	O
to	O
isolate	O
the	O
microphone	B-Application
from	O
shock	O
and	O
handling	O
noise	O
.	O
</s>
<s>
Stating	O
the	O
efficiency	O
of	O
wind	O
noise	O
reduction	O
is	O
an	O
inexact	O
science	O
since	O
the	O
effect	O
varies	O
enormously	O
with	O
frequency	O
,	O
and	O
hence	O
with	O
the	O
bandwidth	O
of	O
the	O
microphone	B-Application
and	O
audio	O
channel	O
.	O
</s>
