Sound Targeting Platform Andrew Lenharth Michael Schaffer Quang Luu CSE 477 April 24, 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 Stepper Motor Drive Output

Stage One Microphones Pickup audio signal Placed one foot apart (56 samples) Mounted to rotating platform Amplifiers Tune microphone frequency response to same level Amplify signal for ADC

Stage One (cont) Filter Band-pass filter (200Hz – 4kHz) Fourth order Sallen-key filter Chained second order low and high pass ADC Two-bit analog to digital Onboard audio codec

Stage Two Correlator Sliding window correlator 64 sample width 192 sample window size

Stage Two (cont) Correlation Threshold Only allow large values through Minimize noise Feedback to adjust level Averaging Module Average of four correlations Eliminate large noise signals Average Threshold Filter out weak averaged signals

Stage Three Aiming Algorithm Scan correlation to find max Decide if arm needs to move Ignore correlations with large values on both sides

Stage Three (cont) Stepper Motor Control Two ICs – Controller and Driver

Tweaking Gain of amplifier Number of samples between microphones Sampling rate of ADC Band of band pass filter Window size of correlator Width of correlator Bit-depth of correlator Bit-depth of ADC Value of Correlator Threshold Value of Averaging Module Threshold Number of averaged correlations

Conclusion Modular Develop in parallel (good) Test separately (good) Timing issues between modules (bad) Many parameters to tweak Try many aiming algorithms