The spectral envelope and its applications

The concept of the spectral envelope was recently introduced as a statistic al basis for the frequency domain analysis and scaling of qualitative-value d time series. In the process of developing the spectral envelope methodolo gy, many other interesting extensions became evident. In this article we ex plain the basic concept and give numerous examples of the usefulness of the technology. These examples include analyses of DNA sequences, finding opti mal transformations for the analysis of real-valued time series, residual a nalysis, detecting common signals in many time series, and the analysis of textures.