Asymmetric windows in digital signal processing

Abstract

Abstract Symmetric windows are widely used in the field of digital signal processing due to their easy design and linear phase property. Nevertheless, symmetry also implies a few potential drawbacks like longer time delay in short-time frequency analysis and some limitations in frequency response. The removal of the symmetry constraint can therefore lead to asymmetric windows better in certain respects. In signal processing, better signal representations and related improved processing performance can be accomplished. In addition, shorter time delay can be achieved with asymmetric windows. This feature is important for contemporary spoken communications in the Internet or mobile networks and all other real-time signal processing applications. The article gives a comprehensive review of the past and current work in the field of asymmetric windows. We elaborate on our work and related efforts of other researchers inspired by the idea of asymmetry. Shorter time delay and some better spectral properties are the most prominent potential of asymmetric windows. However, there are also some other more subtle properties which can improve the performance in specific application contexts (e.g., frequency estimation and detection of closely spaced components in frequency analysis). Several examples of interesting effects of asymmetric windows are presented, followed by empirical evaluations in the fields of pitch modification, shorter time delay audio processing (e.g., speech coding), frequency analysis, speech processing, and FIR filter design. In addition, a detailed comparison of various asymmetric windows found in the literature to widely known symmetric windows is made taking into account several practical and theoretical aspects. Finally, all presented achievements are summarized in a table which provides a complete overview of the current state of this interesting research and application field.