A speech signal preprocessor with wide dynamic range and weak signal enhancement properties
Wen C. Lin, Tzieh-Tsai Luo · The Journal of the Acoustical Society of America · 1983
This paper describes the design, analysis, and experimental evaluation of a speech signal preprocessor. The design utilizes analog and digital hardware as well as software techniques to achieve a wide dynamic range of operation and to enhance the signal resolution for the weak signal. For saving the memory storage area, the recognition logic for ONSET/OFFSET of speech signal is implemented with analog and digital hardware. Two features, namely energy and zero crossing count, are used in the decision making process. The hardware contains the following major elements: a 755N 6-decade log-amplifier by Analog-Device Corp., anti-aliasing filter, a precision full-wave rectifier, analog switches, and a 12-bit Analog-to-Digital converter. The anti-logarithmic operation is implemented with a software subroutine. Its result can then be used as natural data for further processing. The design problems and solutions, and the mathematical analysis for weak signal enhancement are discussed and experimental evaluation results are described. The system has been used to acquire phonetic data; it yields very good results.