Noise curve

Noise curves are a common way to measure and specify background noise in unoccupied buildings and spaces. Their purpose is to produce a single value representation of a complete sound spectrum. International standards organizations (ISO, ANSI and ASA) recognize the need to objectify judgements on the amount of ambient noise in enclosed spaces, and provide us with definitions for various Noise Curves.

Background noise may have several undesirable effects. Noise can be an annoyance that creates fatique and negatively affects productivity, safety and the ability to communicate. Therefore standard methodologies for quantifying noise have been developed. Noise curves reflect different standardized means of creating a single number rating for the background noise spectrum in a space. Different rooms, locations, regulations and applications may allow different acceptable noise ratings. In most cases, the goal is that background noise should not interfere with the purpose of the room, e.g. the noise of an office air-conditioning system and consistent noise of traffic outside the building should not interfere with telephone calls or conversations. In other cases, special noise may also be tolerated or even introduced at higher levels, for example to create acoustic "privacy", or to help mask other more irritating noise sources.

Noise Curves serve as uniform measuring standards and are referred to by many noise regulations covering a variety of locations from concert halls, rock concerts, lecture rooms and offices to clay target shooting ranges. The major four different types of noise curves are:

• Noise Criterion Curves (NC)
• Noise Rating Curves (NR)
• Preferred Noise Criterion Curves (PNC)
• Room Criteria Curves (RC)