An FPGA-Based Electronic Cochlea
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An FPGA-Based Electronic Cochlea M. P. Leong Department of Computer Science and Engineering, The Chinese University of Hong Kong, Shatin, NT, Hong Kong Email: [email protected]
Craig T. Jin Department of Electrical and Information Engineering, The University of Sydney, Sydney, NSW 2006, Australia Email: [email protected]
Philip H. W. Leong Department of Computer Science and Engineering, The Chinese University of Hong Kong, Shatin, NT, Hong Kong Email: [email protected] Received 18 June 2002 and in revised form 1 August 2002 A module generator which can produce an FPGA-based implementation of an electronic cochlea filter with arbitrary precision is presented. Although hardware implementations of electronic cochlea models have traditionally used analog VLSI as the implementation medium due to their small area, high speed, and low power consumption, FPGA-based implementations offer shorter design times, improved dynamic range, higher accuracy, and a simpler computer interface. The tool presented takes filter coefficients as input and produces a synthesizable VHDL description of an application-optimized design as output. Furthermore, the tool can use simulation test vectors in order to determine the appropriate scaling of the fixed-point precision parameters for each filter. The resulting model can be used as an accelerator for research in audition or as the front-end for embedded auditory signal processing systems. The application of this module generator to a real-time cochleagram display is also presented. Keywords and phrases: field programmable gate array, electronic cochlea, VHDL modules.
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The field of neuromorphic engineering has the long-term objective of taking architectures from our understanding of biological systems to develop novel signal processing systems. This field of research, pioneered by Mead [1], has concentrated on using analog VLSI to model biological systems. Research in this field has led to many biologically inspired signal processing systems which have improved performance compared to traditional systems. The human cochlea is a transducer which converts mechanical vibrations from the middle ear into neural electrical discharges, and additionally provides spatial separation of frequency information in a manner similar to that of a spectrum analyzer [2]. It serves as the front-end signal processing for all functions of the auditory nervous system such as auditory localization, pitch detection, and speech recognition. Although it is possible to simulate cochlea models in software, hardware implementations may have orders of magnitude of improvement in performance. Hardware implementations are also attractive when the target applications are on embedded devices in which power efficiency and smallfootprint are design considerations.
Low-frequency sections
High-frequency sections
INTRODUCTION Samples
IIR biquadratic section
IIR biquadratic section
Output 1
Output 2
IIR biquadratic section
Output N
Figure 1: Cascaded IIR biquadratic section used in the Lyon and Mead cochlea mode
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