This glossary has been rolled forwards from previous work by the authors, with some new additions specifically relating to the text of this book. Experience has shown that although some of the terms may be familiar to many readers, they have often been misunderstood or misused. This glossary attempts to clarify the definitions of the terms, at least as used in British English.
A filter applied, usually digitally, which has advanced knowledge of the signal arriving, via delaying the main signal on which it is intended to act – effect before cause through prior knowledge of the cause. See Causal filter.
Filters or loudspeaker systems, for example, where an external power source needs to be applied ...