<s>
Audio	B-Algorithm
signal	I-Algorithm
processing	I-Algorithm
is	O
a	O
subfield	O
of	O
signal	O
processing	O
that	O
is	O
concerned	O
with	O
the	O
electronic	O
manipulation	O
of	O
audio	O
signals	O
.	O
</s>
<s>
Analog	O
processors	O
operate	O
directly	O
on	O
the	O
electrical	O
signal	O
,	O
while	O
digital	B-Architecture
processors	I-Architecture
operate	O
mathematically	O
on	O
its	O
digital	O
representation	O
.	O
</s>
<s>
The	O
motivation	O
for	O
audio	B-Algorithm
signal	I-Algorithm
processing	I-Algorithm
began	O
at	O
the	O
beginning	O
of	O
the	O
20th	O
century	O
with	O
inventions	O
like	O
the	O
telephone	O
,	O
phonograph	O
,	O
and	O
radio	O
that	O
allowed	O
for	O
the	O
transmission	O
and	O
storage	O
of	O
audio	O
signals	O
.	O
</s>
<s>
Claude	O
Shannon	O
and	O
Harry	O
Nyquist	O
's	O
early	O
work	O
on	O
communication	O
theory	O
,	O
sampling	O
theory	O
and	O
pulse-code	B-Algorithm
modulation	I-Algorithm
(	O
PCM	B-Algorithm
)	O
laid	O
the	O
foundations	O
for	O
the	O
field	O
.	O
</s>
<s>
In	O
1957	O
,	O
Max	O
Mathews	O
became	O
the	O
first	O
person	O
to	O
synthesize	O
audio	O
from	O
a	O
computer	O
,	O
giving	O
birth	O
to	O
computer	B-Application
music	I-Application
.	O
</s>
<s>
Major	O
developments	O
in	O
digital	O
audio	O
coding	O
and	O
audio	O
data	O
compression	O
include	O
differential	B-General_Concept
pulse-code	I-General_Concept
modulation	I-General_Concept
(	O
DPCM	B-General_Concept
)	O
by	O
C	O
.	O
Chapin	O
Cutler	O
at	O
Bell	O
Labs	O
in	O
1950	O
,	O
linear	B-Algorithm
predictive	I-Algorithm
coding	I-Algorithm
(	O
LPC	O
)	O
by	O
Fumitada	O
Itakura	O
(	O
Nagoya	O
University	O
)	O
and	O
Shuzo	O
Saito	O
(	O
Nippon	O
Telegraph	O
and	O
Telephone	O
)	O
in	O
1966	O
,	O
adaptive	B-Algorithm
DPCM	I-Algorithm
(	O
ADPCM	B-Algorithm
)	O
by	O
P	O
.	O
Cummiskey	O
,	O
Nikil	O
S	O
.	O
Jayant	O
and	O
James	O
L	O
.	O
Flanagan	O
at	O
Bell	O
Labs	O
in	O
1973	O
,	O
discrete	B-General_Concept
cosine	I-General_Concept
transform	I-General_Concept
(	O
DCT	B-General_Concept
)	O
coding	O
by	O
Nasir	O
Ahmed	O
,	O
T	O
.	O
Natarajan	O
and	O
K	O
.	O
R	O
.	O
Rao	O
in	O
1974	O
,	O
and	O
modified	O
discrete	B-General_Concept
cosine	I-General_Concept
transform	I-General_Concept
(	O
MDCT	O
)	O
coding	O
by	O
J	O
.	O
P	O
.	O
Princen	O
,	O
A	O
.	O
W	O
.	O
Johnson	O
and	O
A	O
.	O
</s>
<s>
LPC	O
is	O
the	O
basis	O
for	O
perceptual	O
coding	O
and	O
is	O
widely	O
used	O
in	O
speech	B-Application
coding	I-Application
,	O
while	O
MDCT	O
coding	O
is	O
widely	O
used	O
in	O
modern	O
audio	O
coding	O
formats	O
such	O
as	O
MP3	B-Application
and	O
Advanced	B-Application
Audio	I-Application
Coding	I-Application
(	O
AAC	O
)	O
.	O
</s>
<s>
This	O
permits	O
signal	O
processing	O
using	O
digital	O
circuits	O
such	O
as	O
digital	B-Architecture
signal	I-Architecture
processors	I-Architecture
,	O
microprocessors	B-Architecture
and	O
general-purpose	O
computers	O
.	O
</s>
<s>
Processing	O
methods	O
and	O
application	O
areas	O
include	O
storage	O
,	O
data	O
compression	O
,	O
music	B-Application
information	I-Application
retrieval	I-Application
,	O
speech	B-Algorithm
processing	I-Algorithm
,	O
localization	O
,	O
acoustic	O
detection	O
,	O
transmission	O
,	O
noise	O
cancellation	O
,	O
acoustic	B-Algorithm
fingerprinting	I-Algorithm
,	O
sound	O
recognition	O
,	O
synthesis	O
,	O
and	O
enhancement	O
(	O
e.g.	O
</s>
<s>
Audio	B-Algorithm
signal	I-Algorithm
processing	I-Algorithm
is	O
used	O
when	O
broadcasting	O
audio	O
signals	O
in	O
order	O
to	O
enhance	O
their	O
fidelity	O
or	O
optimize	O
for	O
bandwidth	O
or	O
latency	O
.	O
</s>
<s>
The	O
audio	B-Algorithm
processor	I-Algorithm
here	O
must	O
prevent	O
or	O
minimize	O
overmodulation	O
,	O
compensate	O
for	O
non-linear	O
transmitters	O
(	O
a	O
potential	O
issue	O
with	O
medium	B-Algorithm
wave	I-Algorithm
and	O
shortwave	O
broadcasting	O
)	O
,	O
and	O
adjust	O
overall	O
loudness	B-Algorithm
to	O
the	O
desired	O
level	O
.	O
</s>
<s>
Audio	O
synthesis	O
is	O
also	O
used	O
to	O
generate	O
human	O
speech	O
using	O
speech	B-Application
synthesis	I-Application
.	O
</s>
<s>
Common	O
effects	O
include	O
distortion	O
,	O
often	O
used	O
with	O
electric	O
guitar	O
in	O
electric	O
blues	O
and	O
rock	O
music	O
;	O
dynamic	O
effects	O
such	O
as	O
volume	O
pedals	O
and	O
compressors	O
,	O
which	O
affect	O
loudness	B-Algorithm
;	O
filters	O
such	O
as	O
wah-wah	O
pedals	O
and	O
graphic	O
equalizers	O
,	O
which	O
modify	O
frequency	O
ranges	O
;	O
modulation	B-Application
effects	O
,	O
such	O
as	O
chorus	O
,	O
flangers	O
and	O
phasers	O
;	O
pitch	O
effects	O
such	O
as	O
pitch	O
shifters	O
;	O
and	O
time	O
effects	O
,	O
such	O
as	O
reverb	O
and	O
delay	O
,	O
which	O
create	O
echoing	O
sounds	O
and	O
emulate	O
the	O
sound	O
of	O
different	O
spaces	O
.	O
</s>
