Physics 434 Module 4

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Physics 434 Module 4

• Acoustic excitation of a physical system time
  domain

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Frequency domain

• Last week you measured the frequency domain
  response to the system
• where, ?2?f, and G(?) is the (complex)
  response. (Why complex?).

G(?)
Hout(?)
Hin(?)
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Review the pre-test
What is the frequency composition of these
signals?
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Frequencies in a pulse
Note exactly the same as a single-slit
diffraction pattern
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More generally
Any time-varying signal is composed of a spectrum
of frequencies
Where H(?) is the Fourier transform, or frequency
domain representation of the signal
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The response to a time-varying signal
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Time domain Goals

• Apply a pulse to the system, measure the response
• Adapt the test VI to accumulate and average
  multiple shots
• Understand the signal processing requirements,
  and capabilities of the AT-E data acquisition
  board
• Use a Fast Fourier Transform (FFT) VI to obtain
  the spectrum
• Understand how a FFT works

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Setup almost same as Module 3
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Triggering!
GPCTR0_OUT
digital ground
TRIG1
To scope and speaker in
To scope and microphone in
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Run the demo VI
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A second advantage signal averaging
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Next week FFT