Noise Curves

Noise Curves

Noise curves specify the acoustic ambient noise in an indoor environment. The unoccupied room is measured to produce a single maximum value across the complete sound spectrum. This value is used to determine if the ambient noise will be annoying to people occupying the room. The value also influences the intelligibility of speech.


  • Noise Criteria NC (ANSI S12.2-2008)
  • Room Noise Criteria RNC (ANSI S12.2-2008)
  • Noise Rating NR (ISO 1996)


Noise curves are used to measure and specify background noise in unoccupied buildings and spaces.

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.

Background noise that is annoying creates fatigue and can negatively affect productivity and safety. Too much noise also affects the ability to communicate. Therefore standard methodologies for quantifying such noise have been developed.

Different rooms, locations, regulations and applications may allow different acceptable noise ratings.


Methods and Standards

For all ambient noise measurement methods, a measured noise spectrum is superimposed on a family of contours (or curves).

NC Result
Result: NC45


Noise Curvesについて詳しくはこちら


The XL2 Acoustic and Audio Analyzer, with the Spectral Limit Option installed, supports these Noise Curve types:

NC Result

The XL2 measures all noise curve types at the same time, thus you can switch to your required report after the measurement. The result also indicates the frequency band with the highest noise rating between 16 Hz and 8 kHz.



NC-2008、NC-1995規格のNC値の場合、SIL値(speech interference level)が、オクターブバンド500 Hz、1000 Hz、2000 Hz、4000 Hzにおける音圧レベルを平均して計算されます。The XL2 Analyzer includes any tangency method adaptation as applicable.



XL2 Set for Noise Curves Testing

XL2 Kit for Noise Curves Measurements

  • XL2 オーディオ&アコースティックアナライザ
  • スペクトラムリミット・オプション
  • M2211 測定用マイクロホン
  • XL2用ASDケーブル
  • XL2用ACアダプタ
  • 校正証明書x2
  • Exel システムケース