Noise measurement
Encyclopedia
Noise measurement is carried out in various fields.
In acoustics
, it can be for the purpose of measuring environmental noise
, or part of a test procedure using white noise
, or some other specialised form of test signal.
In electronics
it relates to the sensitivity of communications systems, the purity of signals, or the quality of audio systems. The concept is to define the noise level below which signals cannot reliably be detected. It can be thought of as uncertainty
of the information being carried over a communications channel.
In audio systems and broadcasting specific methods are used to obtain subjectively valid results in order that different devices and signal paths may be compared regardless of the differing spectral distribution and temporal properties of the noise that they generate. In particular, the ITU-R 468 noise weighting
was devised specifically for this purpose, and is widely used for professional audio and broadcast measurements.
In acoustics
Acoustics
Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...
, it can be for the purpose of measuring environmental noise
Environmental noise
Environmental noise is the summary of noise from transport, industrial and recreational activities.The definition is pursuant to the directive 2002/49/EC article 10.1. This directive should give a common approach intended to avoid, prevent or reduce the harmful effects of environmental noise. The...
, or part of a test procedure using white noise
White noise
White noise is a random signal with a flat power spectral density. In other words, the signal contains equal power within a fixed bandwidth at any center frequency...
, or some other specialised form of test signal.
In electronics
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
it relates to the sensitivity of communications systems, the purity of signals, or the quality of audio systems. The concept is to define the noise level below which signals cannot reliably be detected. It can be thought of as uncertainty
Uncertainty
Uncertainty is a term used in subtly different ways in a number of fields, including physics, philosophy, statistics, economics, finance, insurance, psychology, sociology, engineering, and information science...
of the information being carried over a communications channel.
In audio systems and broadcasting specific methods are used to obtain subjectively valid results in order that different devices and signal paths may be compared regardless of the differing spectral distribution and temporal properties of the noise that they generate. In particular, the ITU-R 468 noise weighting
ITU-R 468 noise weighting
ITU-R 468 is a standard relating to noise measurement, widely used when measuring noise in audio systems. The standard defines a weighting filter curve, together with a quasi-peak rectifier having special characteristics as defined by specified tone-burst tests...
was devised specifically for this purpose, and is widely used for professional audio and broadcast measurements.
Standards
There are a number of standards for noise measurement, each with a different goal or focus, including:- Standard:ITU-R BS 468 widely used in Broadcasting and professional Audio.
- Standard:IEC A-weighting is widely used in Environmental Noise measurement.
- Standard:CCIR recommendation 468-4 is now maintained as ITU-R BS 468
- Standard:CCITT 0.41 refers to 'Psophometric weightingPsophometric weightingPsophometric weighting refers to any weighting curve used in the measurement of noise. In the field of audio engineering it has a more specific meaning, referring to noise weightings used especially in measuring noise on telecommunications circuits...
' used on telephone circuits. - Standard:CCITT P53 is now continued as CCITT0.41
- Standard:BS 6402:1983 specifies Personal sound exposure meters.
- Standard:BS 3539:1968 specifies Sound level meterSound level meterSound level meters measure sound pressure level and are commonly used in noise pollution studies for the quantification of almost any noise, but especially for industrial, environmental and aircraft noise. However, the reading given by a sound level meter does not correlate well to...
s for motor vehicle noise. - Standard:BSEN 60651 supersedes BS 5969:1981 Sound level meterSound level meterSound level meters measure sound pressure level and are commonly used in noise pollution studies for the quantification of almost any noise, but especially for industrial, environmental and aircraft noise. However, the reading given by a sound level meter does not correlate well to...
s
See also
- Audio quality measurementAudio quality measurementAudio quality measurement seeks to quantify the various forms of corruption present in an audio system or device. The results of such measurement are used to maintain standards in broadcasting, to compile specifications, and to compare pieces of equipment....
- Rumble measurement
- Noise dosimeterNoise dosimeterA noise dosimeter or noise dosemeter is a specialized sound level meter intended specifically to measure the noise exposure of a person integrated over a period of time; usually to comply with Health and Safety regulations such as the Occupational Safety and Health or EU Directive 2003/10/EC.-...
- Noise (environmental)
- Noise (economic)Noise (economic)Economic noise, or simply noise, describes a theory of pricing developed by Fischer Black. To Black, noise is the opposite of information. Sometimes it's hype, other times it's inaccurate ideas, other times it's inaccurate data; noise has many forms...
- Noise musicNoise musicNoise music is a term used to describe varieties of avant-garde music and sound art that may use elements such as cacophony, dissonance, atonality, noise, indeterminacy, and repetition in their realization. Noise music can feature distortion, various types of acoustically or electronically...
- Noise pollutionNoise pollutionNoise pollution is excessive, displeasing human, animal or machine-created environmental noise that disrupts the activity or balance of human or animal life...
- ITU-R 468 noise weightingITU-R 468 noise weightingITU-R 468 is a standard relating to noise measurement, widely used when measuring noise in audio systems. The standard defines a weighting filter curve, together with a quasi-peak rectifier having special characteristics as defined by specified tone-burst tests...
- A-weightingA-weightingA Weighting curve is a graph of a set of factors, that are used to 'weight' measured values of a variable according to their importance in relation to some outcome. The most commonly known example is frequency weighting in sound level measurement where a specific set of weighting curves known as A,...
- Weighting filterWeighting filterA weighting filter is used to emphasise or suppress some aspects of a phenomenon compared to others, for measurement or other purposes.- Audio applications :...
- Equal-loudness contourEqual-loudness contourAn equal-loudness contour is a measure of sound pressure , over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. The unit of measurement for loudness levels is the phon, and is arrived at by reference to equal-loudness contours...
- Cosmic microwave background radiationCosmic microwave background radiationIn cosmology, cosmic microwave background radiation is thermal radiation filling the observable universe almost uniformly....