A space domain complex envelope

Abstract

Sound visualization tools, for example, beam forming and acoustic holography, exhibit the spatial look of sound in time or frequency domain. However, they normally require a significant amount of computation time to draw well the sound picture in space. The picture contains a great deal of information: Sound pressure distribution, intensity pattern, or energy information with respect to space. The information is often far more than what we need in practice. For example, when we want to know only the location of the sound sources and somewhat averaged sound pressure distribution, we need a means that can provide only what we need. The complex envelope in time domain can be a good starting idea to deal with the problems we have. A method to generate a spatial domain envelope has been theoretically developed. We found that the method not only has an advantage to show rather simple spatial sound distribution, but also reduce significantly the computation time. The latter makes it possible to see the sound picture faster than before: About ten times faster. This method has been applied to many practical examples: For example, sound from a musical instrument and sound from machinery.