Application of wavelet transform in photoacoustic spectroscopy

Photoacoustic (PA) spectroscopy is a combination of optical spectroscopy and calorimetry [58]. It is a technique for studying those materials that are unsuitable for the conventional transmission or reflection methodologies. It can be used to measure thermal and elastic properties of materials, to study chemical reactions, to measure the thickness of layers and thin films, and to perform a variety of other non-spectroscopic investigations. This technique can be applied to different types of inorganic, organic and biological materials in the gas-, liquid-, or solid phase. Nowadays, PA spectroscopy is mainly employed for material characterization [59]. Compared with other spectroscopic techniques, PA spectroscopy provides a non-destructive analysis and does not require any sample preparation. 

Recently, some researchers have tried to employ WT in processing signals from PA spectroscopy, and satisfactory results were obtained [60,61]. The major role of WT in PA spectroscopy is to filter simultaneously the noise and 

In conclusion, WT has been applied successfully for data processing in various fields of spectroscopic studies. We can see that more WT - related applications in spectroscopy will be developed in the near future when more spectroscopists become aware of the unusual properties of wavelets. Raman spectroscopy, electronic spectroscopy, rotational spectroscopy, and vibrational spectroscopy could be new areas to be explored and no application of WT has yet been reported in such areas. 

Barclay, R.F. Bonner and I.P. Hamilton. Application of Wavelet Transforms to Experimental Spectra Smoothing, DENOISING, and Data Set Compression, Analytical Chemistry. 69 (1997), 78-90. 

Willson and T.H. Edwards, Sampling and Smoothing of Spectra, Applied Spectroscopic Review. 12 (1976), 1-81. 

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