Dictionary learning of sound speed profiles

TitleDictionary learning of sound speed profiles
Publication TypeJournal Article
Year of Publication2017
AuthorsBianco M., Gerstoft P
JournalJournal of the Acoustical Society of America
Date Published2017/03
Type of ArticleArticle
ISBN Number0001-4966
Accession NumberWOS:000398962500059
Keywordsdictionaries; Empirical orthogonal functions; geoacoustic inversion; k-svd; overcomplete; shallow-water

To provide constraints on the inversion of ocean sound speed profiles (SSPs), SSPs are often modeled using empirical orthogonal functions (EOFs). However, this regularization, which uses the leading order EOFs with a minimum-energy constraint on the coefficients, often yields low resolution SSP estimates. In this paper, it is shown that dictionary learning, a form of unsupervised machine learning, can improve SSP resolution by generating a dictionary of shape functions for sparse processing (e.g., compressive sensing) that optimally compress SSPs; both minimizing the reconstruction error and the number of coefficients. These learned dictionaries (LDs) are not constrained to be orthogonal and thus, fit the given signals such that each signal example is approximated using few LD entries. Here, LDs describing SSP observations from the HF-97 experiment and the South China Sea are generated using the K-SVD algorithm. These LDs better explain SSP variability and require fewer coefficients than EOFs, describing much of the variability with one coefficient. Thus, LDs improve the resolution of SSP estimates with negligible computational burden. (C) 2017 Acoustical Society of America.

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