GB/T 3239 - 1982 Focusing on the representation of sound and noise intensity in the air. It covers both subjective and objective representations. It makes it clear that subjective feelings are related to the perception characteristics of sound by the human ear. Objective representations are based on physical acoustic parameters. Specify instrument requirements for objective measurement, measurement environmental conditions, such as sound level meter accuracy, background noise control. Introduce concepts and evaluation methods such as loudness and annoyance involved in subjective evaluation. The standard provides a unified specification for a comprehensive understanding and accurate description of sound and noise intensity in the air, and helps acoustic research, environment noise assessment and related standard formulation.