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Automated estimation of white Gaussian noise level in a spectrum with or without spike noise using a spectral shifting technique

TitleAutomated estimation of white Gaussian noise level in a spectrum with or without spike noise using a spectral shifting technique
Publication TypeJournal Article
Year of Publication2006
AuthorsSchulze, HG, Yu, MML, Addison, CJ, Blades, MW, Turner, RFB
JournalApplied Spectroscopy
Volume60
Pagination820-825
Date PublishedJul
Type of ArticleArticle
ISBN Number0003-7028
KeywordsALGORITHM, automated noise determination, DETECTION LIMITS, limit of detection, NOISE, noise estimation, RAMAN, REMOVAL, signal-to-noise ratio, spectral noise, standard deviation
Abstract

Various tasks, for example, the determination of signal-to-noise ratios, require the estimation of noise levels in a spectrum. This is generally accomplished by calculating the standard deviation of manually chosen points in a region of the spectrum that has a flat baseline and is otherwise devoid of artifacts and signal peaks. However, an automated procedure has the advantage of being faster and operator-independent. In principle, automated noise estimation in a single spectrum can be carried out by taking that spectrum, shifting a copy thereof by one channel, and subtracting the shifted spectrum from the original spectrum. This leads to an addition of independent noise and a reduction of slowly varying features such as baselines and signal peaks; hence, noise can be more readily determined from the difference spectrum. We demonstrate this technique and a spike-discrimination variant on white Gaussian noise, in the presence and absence of spike noise, and show that highly accurate results can be obtained on a series of simulated Raman spectra and consistent results obtained on real-world Raman spectra. Furthermore, the method can be easily adapted to accommodate heteroscedastic noise.

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