Efficient coding of natural sounds


The auditory system encodes sound by decomposing the amplitude signal arriving at the ear into multiple frequency bands whose center frequencies and bandwidths are approximately exponential functions of the distance from the stapes. This organization is thought to result from the adaptation of cochlear mechanisms to the animal's auditory environment. Here we report that several basic auditory nerve fiber tuning properties can be accounted for by adapting a population of filter shapes to encode natural sounds efficiently. The form of the code depends on sound class, resembling a Fourier transformation when optimized for animal vocalizations and a wavelet transformation when optimized for non-biological environmental sounds. Only for the combined set does the optimal code follow scaling characteristics of physiological data. These results suggest that auditory nerve fibers encode a broad set of natural sounds in a manner consistent with information theoretic principles.

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Figure 1: Auditory filters derived from efficient coding of different natural sounds classes.
Figure 2: Filter power spectra.
Figure 3: Efficient coding of a combined sound ensemble.
Figure 4: Principal components of natural sounds.
Figure 5: Control analyses.
Figure 6: Time–frequency analysis.
Figure 7: Comparison of filter population characteristics to physiological data.
Figure 8: Predicted bandwidth versus frequency curves assuming equalization of spectral power across bandwidths.


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The author thanks C. Olson, B. Olshausen and L. Holt for discussions and feedback on the manuscript.

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Correspondence to Michael S. Lewicki.

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Lewicki, M. Efficient coding of natural sounds. Nat Neurosci 5, 356–363 (2002). https://doi.org/10.1038/nn831

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