
U.S.
Patent
Jan.
30,
2007
Sheet
12
0f
13
US
7,170,404
B2
>
1
> )
DD)
MICROPHONE
8
l
ANALOG
TO
/\12
DIGITAL
CONVERSION
J,
123
EXPECTED
TONE
I
BAND PASS
/\
122
,\
FREQUANCY
INPUT
FILTERING
l
AMPLITUDE
/\124
DETECTING
i
SAMPLE
/\
126
DECIMATION
l
PULSE
MATCHING
/\128
FILTERING
132
’\
EXPECTED
SEQUENCE
ENSEMBLE
p130
LENGTH
INPUT
’
AvERAGING
136
PSEUDO
-
RANDOM
PATTERN
MATCHING
/\134
’\
SEQUENCE
INPUT
'
CORRELATION
I40
’\
THRESHOLD
DETECTION
p138
INPuT
’
DECISION
DETECTION
SIGNAL
F:
2.
LE
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