Voice Preprocessing System Incorporating a Real-Time Spectrum Analyzer with Programmable Switched-Capacitor Filters.
MITRE CORP BEDFORD MA
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As part of a speaker verification program for BISS Base Installation Security System, a test system is being designed with a flexible preprocessing system for the evaluation of voice spectrumverification algorithm related problems. The main part of this report covers the design, construction, and testing of a voice analyzer with 16 integrating real-time frequency channels ranging from 300 Hz to 3 KHz. The bandpass filter response of each channel is programmable by NMOS switched capacitor quad filter arrays. Presently, the accuracy of these units is limited to a moderate precision by the finite steps of programming. However, repeatability of characteristics between filter units and sections seems to be excellent for the implemented fourth-order Butterworth bandpass responses. We obtained a 0.1 dB linearity error of signal detection and measured a signal-to-noise ratio of approximately 70 Db. The proprocessing system discussed includes preemphasis filter design, gain normalizer design, and data acquisition system design as well as test results. Author
- Administration and Management
- Voice Communications