Division 2.6.1 Definitions and symbols

Some important terms are described here by the general meanings attributed to them in this document. The list is not exhaustive; only expressions and acronyms used frequently are included. Others are described where they first occur.

The mathematical symbols (listed after the terms) are the main ones used in equations in the main text. Other symbols used locally in both the text and the appendices are defined where they are used.

The reader is reminded periodically of the interchangeability of the words sound and noise in this document. Although the word noise has subjective connotations — it is usually defined by acousticians as ‘unwanted sound’ — in the field of aircraft noise control it is commonly taken to mean just sound — airborne energy transmitted by acoustic wave motion. The symbol → denotes cross references to other terms included in the list.