You can use the continuous wavelet transform (CWT) to analyze how the frequency content of a signal changes over time. For two signals, wavelet coherence reveals common time-varying patterns. For images, continuous wavelet analysis shows how the frequency content of an image varies across the image and helps to reveal patterns in a noisy image.
Use Wavelet Toolbox™ to obtain the CWT of signals and images. You can use the CWT to obtain the wavelet coherence between two signals. You can also reconstruct time-frequency localized approximations to signals.