Noise Curves

Background noise spectral ratings

Noise curves specify the acoustic ambient noise in an indoor environment. Typical disturbing noises are the background noise caused by an air conditioning system as well as noises from heating or ventilation systems (HVAC).

Noise Criteria NC
Room Noise Criteria RNC
Room Criteria RC

Noise Rating NR
Grenzkurven GK

How to measure and report

Background noise that is annoying creates fatigue and can negatively affect productivity and safety. Too much noise also affects the ability to communicate, thus the intelligibility of speech. Therefore, standard methodologies for quantifying such noise have been developed. Different rooms, locations, regulations and applications may allow individual 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 should not interfere with telephone calls or conversations.

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Measuring Noise Curves

The XL2 Acoustic Analyzer measures the background noise spectrum of the unoccupied room in accordance with the standard. The resulting frequency spectrum gets classified by the Noise Curves. The noise rating is designated as the value of the lowest noise curve not “touched” by the measured noise spectrum in 1 dB steps.

This allows a quick verification if the background noise in the room under test meets the specified requirements and shall not annoy people occupying the room. The Noise Curve functionality is optional and requires that the Spectral Limits Option be installed on the instrument.

The XL2 indicates the frequency band with the highest noise curve rating between 16 Hz and 8 kHz. Additionally, the instrument calculates also the speech interference level (SIL) result by averaging the octave-band sound pressure levels at 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz.

The XL2 Acoustic Analyzer measures the following Noise Curves:
- Noise Criteria NC (ANSI/ASA S12.2-2019)
- Room Noise Criterion RNC (ANSI/ASA S12.2-2019)
- Room Criteria RC (ANSI/ASA S12.2-2019)
- Noise Rating NR (ISO/R 1996-1971)
- PNC Rating (ASA 1971)

Data Analyzing and Reporting

Room Acoustics Reporter offers a dedicated solution for generating standardized noise curve reports. The software calculates the average background noise spectrum in the room. This may be compared with the target range – based on the usage of the room. The software supports data recorded by the measurement function Spectrum (RTA) as well as the specific XL2 functions Noise Curves, 1/12 Octave and Cinema Meter.
Room Acoustics Reporter supports the following Noise Curve standards:
- Noise Criteria NC (ANSI/ASA S12.2-2019)
- Room Noise Criterion RNC (ANSI/ASA S12.2-2019)
- Noise Rating NR (ISO/R 1996-1971)
- Grenzkurven GK (DIN 15996:2020)
To Room Acoustic Reporter

Configuration

XL2 Kit for Noise Curves Measurements

including
- XL2 Acoustic Analyzer
- Spectral Limits Option for XL2
- Room Acoustics Reporter 365 for XL2 (annual subscription service)
- M2211 Measurement Microphone
- 1/2″ Windscreen 90 mm
- ASD Cable
- Mains Power Adapter
- Calibration Certificates IEC 61672-3
- System Case