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Spatial Power Spectrum Analyzer

Spatial Power Spectrum Analyzer. Outline. Introduction Objective Review Original Design Describe project build and functional tests Discuss successes and challenges Recommendations Questions. Introduction . Detect the sound source and interface to computer

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Spatial Power Spectrum Analyzer

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  1. Spatial Power Spectrum Analyzer

  2. Outline • Introduction • Objective • Review Original Design • Describe project build and functional tests • Discuss successes and challenges • Recommendations • Questions

  3. Introduction • Detect the sound source and interface to computer • Tell the direction of the sound source • Apply to “smart” video cameras that follow sound source • Apply to museum displays that detect approaching people

  4. Objective • A breakout box • detect and receive an input speech signal • An analyzer • calculate the location of the speech source • Labview • Benefits • Provides interactive control to other devices and technologies • Low cost solution of spatial power spectrum detection

  5. Sound Souse Microphone array Power A/D converter LabView Matlab Display screen Review Original Design

  6. Describe project build • Formulas • Equipment • Set up

  7. Formulas • D x cos(a) = dt x S • D:distance between each two microphones • 10cm, 20cm, 50cm, 100cm • a: angle of the direction • Unknown! • dt: time delay between each pair of microphones separated distance • Calculated • S: the sound speed • 340-344 m/s

  8. For loop For t’=1:N For t=1 : N S(t’)=S|S1(t) – S2(t-t’)|2 Delay = t’ when S is maximum FFT ‘a’ = IFFT[fft(S1)xfft(S2)*] delay = index (max(|a|)) Find time delay

  9. S(t) t S(t-t’) t t’

  10. S(t) t S(t-t’) t t’

  11. Sampling Rate • At least 3.3 KHz for D=1m • D x cos(j) = dt x S • 1m x cos(0) / (340m/s)= dt = 0.003s = 330Hz • We use 105 samples/sec

  12. Hardware Microphones A/D Converters Power Amplification Sound Source PC Monitor Software Labview Equipments

  13. Labview

  14. Circuit

  15. Microphone Array

  16. Set up

  17. Functional test • Using Matlab testing mathematic logic • Calibrate the microphones • Testing angles • With different distances between microphones • With different distances between microphones and sound source

  18. ANGLE ACCURACY TEST RESULTS (ANGLES GIVEN IN DEG.)

  19. Sampling rate to 100kHz Two different methods for calculating time delay Filter out background noises Consistent angle measurements Discuss successes and challenges

  20. Recommendations • Spend more time testing/designing mics/amp circuit – focus on relative microphone sensitivity as well as overall output levels • Success rate with different sound sources • How much do room acoustics affect performance?

  21. Questions • ?

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