Time–frequency analysis

thumb|upright=1.35|Spectrogram of the spoken words "nineteenth century". Frequencies are shown increasing up the vertical axis, and time on the horizontal axis. The legend to the right shows that the color intensity increases with the density. thumb|upright=1.35|A 3D spectrogram: The RF spectrum of a battery charger is shown over time

A wavelet is a wave-like oscillation with an amplitude that begins at zero, increases or decreases, and then returns to zero one or more times. Wavelets are termed a "brief oscillation". A taxonomy of wavelets has been established, based on the number and direction of its pulses. Wavelets are imbued with specific properties that make them useful for signal processing. thumb|Seismic wavelet

discrete Fourier transform with short overlapping windows

design method of discrete wavelet transforms

particular representation of a signal

linear transformation generalizing the Fourier transform, used in the area of harmonic analysis

algorithm

function of propagation delay and Doppler frequency, representing the distortion of a returned pulse due to the receiver matched filter of the return from a moving target

free software for audio spectrum anlysis

techniques and methods in signal processing