Evaluation of Neuromorphic Spike Encoding of Sound Using Information Theory

Abstract

The problem of spike encoding of sound consists in transforming a sound waveform into spikes. It is of interest in many domains, including the development of audio-based spiking neural networks, where it is the first and most crucial stage of processing. Many algorithms have been proposed to perform spike encoding of sound. However, a systematic approach to quantitatively evaluate their performance is currently lacking. We propose the use of an information-theoretic framework to solve this problem. Specifically, we evaluate the coding efficiency of four spike encoding algorithms on two coding tasks that consist of coding the fundamental characteristics of sound: frequency and amplitude. The algorithms investigated are: Independent Spike Coding, Send-on-Delta coding, Ben's Spiker Algorithm, and Leaky Integrate-and-Fire coding. Using the tools of information theory, we estimate the information that the spikes carry on relevant aspects of an input stimulus. We find disparities in the coding efficiencies of the algorithms, where Leaky Integrate-and-Fire coding performs best. The information-theoretic analysis of their performance on these coding tasks provides insight on the encoding of richer and more complex sound stimuli.

Efficiency metrics for auditory neuromorphic spike encoding techniques using information theory

“…In contrast to decoding, information theory measures the total information captured by the spikes without introducing models or additional processing that can cause information loss. Information theory has been used for example in [7] and [10] to evaluate spike encoding techniques.…”

“…An introductory work is available in[7] 2. Discrete-time signal processing notation is used where n is the integer sample index of the time-sampled signal x.…”