Abstract: Apparatus and methods of spectral searching that employ wavelet coefficients as the basis for the searching. The disclosed apparatus and methods employ a wavelet lifting scheme to transform spectroscopic data corresponding to an unknown pure material/mixture to a vector of wavelet coefficients, compare the wavelet coefficient vector for the unknown pure material/mixture with a library of wavelet coefficient vectors for known pure materials/mixtures, and identify the closest match to the unknown pure material/mixture based on the comparison of wavelet coefficient vectors.

Abstract: Apparatus and methods of spectral searching that employ wavelet coefficients as the basis for the searching. The disclosed apparatus and methods employ a wavelet lifting scheme to transform spectroscopic data corresponding to an unknown pure material/mixture to a vector of wavelet coefficients, compare the wavelet coefficient vector for the unknown pure material/mixture with a library of wavelet coefficient vectors for known pure materials/mixtures, and identify the closest match to the unknown pure material/mixture based on the comparison of wavelet coefficient vectors.

Abstract: A radial or azmuthal non-resonant flow-through optoacoustic cell is operated without windows, completely eliminating the window background interference. The cell is constructed of an elongated tube the length of which is 34.times.10.sup.3 cm.times.1/f, where f is the light source modulating frequency and is made of conducting material which is perforated along the center one-half length with holes. A metalized sheath surrounds this center region to form a capacitor microphone.