Acoustic and electromagnetic wave phenomena may seem to have a proper formal representation in field theory dating from the 19th century, founded on the mathematics of complex functions. This paper shows, however, that when replacing the classical spectrum-domain approach related to the assumption of harmonic timeform of signals, with a time-domain approach imposing no restriction as to the class of time evolution of source and field signals, it is possible to perform such a description of

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... description of physical effects and their local, causality-driven mechanisms, that results in new revelations as to the role of both the physical medium and the wave source in initiating and conveying phenomena, otherwise perfectly familiar, that carry energy and preserve signal waveform. It appears that causality and locality are a core of dynamic linear phenomena in physical continua, leading to the creation of doubly-dynamic states that are observed, at the approach, in "frozen" conditions.