Methods and systems are provided for transmitting and receiving photon density waves to and from tissue, and processing the received waves using wavelet transforms to identify non-physiological signal components and/or identify physiological conditions. A pulse oximeter may receive the photon density waves from the tissue to generate a signal having phase and amplitude information. A phase signal may be proportional to a scattering by total particles in the tissue, and an amplitude signal may correlate to an absorption by certain particles, providing information on a ratio of different particles in the tissue. Processing the phase and amplitude signals with wavelet transforms may enable an analysis of signals with respect to time, frequency, and magnitude, and may produce various physiological data. For example, non-physiological noise components may be identified, and certain physiological conditions may be identified by processing scalograms of the original signals with patterns corresponding to certain physiological conditions.
