Final Project Search and Rescue

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Final ProjectSearch and Rescue
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Objective
As part of the search and rescue contest, you
will need to find a high frequency (4 6 kHz)
sound located somewhere in the room. There will
be low frequency (lt 500 Hz) sound source in the
room, also.
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BRAINSTORMING
How can we locate a sound source?????
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Microphone
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Microphone
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Sound Pressure Levels

• Sound pressure levels are measured in Pascals
  (Pa).
• If someone is yelling at you from 2-3 feet away
  that is about 1 Pa i.e. (1 Volt out of
  microphone)
• If he is speaking in a normal voice, that would
  be about 0.1 Pa. (100 mV out of microphone)
• If he is whispering (very softly) that might be
  1 mPa.
• (1 mV out of microphone)

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Gain Amplfier
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TLC2272
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CD4066
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CD4066
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74HC4051
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Bandpass Filter
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Transfer Characteristic
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Design Equations
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Absolute Value
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Path Difference
Sound Source
If l0 gtgt d, Dl d sin(f)
l2
l0
l1
f
Left Mic
Right Mic
d
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Phase Delay

• If c speed of sound 340 m/s, then Dt Dl /
  c.
• arc_sin(c Dt) / d
• So, how can I measure Dt????

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Phase Comparison
Vphase Vdd (Dt / T) So Dt Vphase T / Vdd
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TLC3702
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Tone Decoder IC
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LM567
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The sky is the limit!