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.