This invention relates to an improved adaptive spectral estimator for estimating the spectral components in a signal containing both an information signal, such as speech and noise. The improvements relate to a noise power estimator (3) and a computationally efficient gain calculation method. The adaptive spectral estimator is particularly suited to implementation using digital signal processing and can be used to provide improved spectral estimates of the information signal. It can be combined with a speech or voice recognition system. A further object of the invention is to provide an accurate method for voice detection.