Pressure wave propagation methods: a rich history and a bright future

The pressure wave propagation (PWP) method was developed 25 years ago to study space charges in solid dielectrics. This method has been a powerful tool in this field of research but has also proved its efficiency in adjacent fields for the characterization of materials or processes. In this paper the history of this method and its principle are recalled. The pulsed electro-acoustic (PEA) method, which can be physically described in a similar way and for which data can be analyzed in an equivalent fashion, is also presented. Examples of applications and developments are given which indicate the direction which these methods might take in the future