Sound Targeting Platform

1
Sound Targeting Platform
CSE 477

• Andrew Lenharth
• Michael Schaffer
• Quang Luu

May 22, 2001
2
Introduction

• Multi-purpose platform
• Video conferencing
• Spotlighting
• Security applications
• Aims at sound source
• Microphones pick up sound
• Correlator locates source
• Stepper motors drive arm

3
Physical Layout
Base Platform Rotating Platform Microphone
Placement
4
Modular Design

• Three Stages
• Audio Input Filter and Amplification
• Correlation and Filtering
• Aiming and Stepper Motor Drive Output

5
Stage One - Microphone

• Microphones
• Placed 54 samples apart (1.05 feet)
• 1.3 grams

6
Stage One - Amplifier

• Amplifiers
• Amplify signal to line level for ADC

7
Stage One - Filter

• Filter
• Band-pass filter (200Hz 4kHz)
• Fourth order Sallen-key filter
• Chained second order low and high pass

8
Stage One ADC

• ADC
• Audio codec on XSV-300
• Codec outputs 20-bit 48kHz samples
• Threshold
• Level above ambient noise
• Eliminate noise
• Output 2-bit (preserve phase information)

9
Stage Two - Correlator

• Correlator
• Sliding window correlator
• 64 sample width
• 108 sample window size
• 3 stage pipeline

10
Stage Two Correlator
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Stage Two - Threshold

• Correlation Threshold
• Convert 7-bit signed input to 5-bit output
• Removes negative correlation

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Stage Three - Aim

• Aiming Algorithm
• Scans correlation data as correlator runs
• Finds max value and index of correlation
• Accumulates 32 good max values before outputting
  index
• Uses sliding level max criteria to only choose a
  max that is near levels of recent past maxes.

13
Stage Three Aim
14
Stage Three Motor Control

• Stepper Motor Control
• Two ICs Controller and Driver

15
Simulation

• Simulated design in Matlab to experimentally
  discover good parameters.

Bit-depth of ADC 8 bits Correlator
Threshold 50 Averager Threshold 50 Averaged
Correlations 4 Correlator Width 64 Correlator
Window 128
16
Simulation (cont)

• Refined correlator parameters to discover it is
  actually possible to find the source.

Bit-depth of ADC 2 bits Correlator
Threshold 80 Averager Threshold 50 Averaged
Correlations 1 Correlator Width 64 Correlator
Window 108
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Parameters

• Gain of amplifier 56.6 dB
• Number of samples between microphones 54
  samples
• Sampling rate of ADC 48 kHz
• Band of band pass filter 200 Hz 4 kHz
• Window size of correlator 108 samples
• Width of correlator 64 samples
• Bit-depth of correlator 2 bits
• Bit-depth of ADC 20 bits
• Value of Correlator Threshold minimum 0
  (variable)
• Number of valid correlations before movement
  8,000

18
Reviewer Comments

• Aiming Algorithm Jitter
• Mover Module only allows motor to be driven if we
  didnt move one step last time
• Frequency of the Step Signal
• Mover Module drives stepper motor at 100Hz. (5kHz
  Max)

19
Current Status
20
Current Status (cont)

• Correlator needs more testing
• Aiming algorithm connection to accumulator needs
  to be implemented
• Codec interface needs testing
• Stepper motor control circuit needs to be built
  so it doesnt melt breadboard