Sound Targeting Platform Andrew Lenharth Michael Schaffer Quang Luu CSE 477 May 22, 2001

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

Physical Layout Base Platform Rotating Platform Microphone Placement

Modular Design Three Stages Audio Input – Filter and Amplification Correlation and Filtering Aiming and Stepper Motor Drive Output

Stage One - Microphone Microphones Placed 54 samples apart (1.05 feet) 1.3 grams

Stage One - Amplifier Amplifiers Amplify signal to line level for ADC

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

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)

Stage Two - Correlator Correlator Sliding window correlator 64 sample width 108 sample window size 3 stage pipeline

Stage Two – Correlator

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

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.

Stage Three – Aim

Stage Three – Motor Control Stepper Motor Control Two ICs – Controller and Driver

Simulation Simulated design in Matlab to experimentally discover good parameters. Bit-depth of ADC8 bits Correlator Threshold50 Averager Threshold50 Averaged Correlations4 Correlator Width64 Correlator Window128

Simulation (cont…) Refined correlator parameters to discover it is actually possible to find the source. Bit-depth of ADC2 bits Correlator Threshold80 Averager Threshold50 Averaged Correlations1 Correlator Width64 Correlator Window108

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

Reviewer Comments Aiming Algorithm Jitter Mover Module only allows motor to be driven if we didn’t move one step last time Frequency of the Step Signal Mover Module drives stepper motor at 100Hz. (5kHz Max)

Current Status

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 doesn’t melt breadboard