A 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. An important example is

frequency Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...

weighting in sound level measurement where a specific set of weighting curves known as A-, B-, C-, and D-weighting as defined in IEC 61672 are used. Unweighted measurements of sound pressure do not correspond to perceived loudness because the human ear is less sensitive at low and high frequencies, with the effect more pronounced at lower sound levels. The four curves are applied to the measured sound level, for example by the use of a

weighting filter A weighting filter is used to emphasize or suppress some aspects of a phenomenon compared to others, for measurement or other purposes. Audio applications In each field of audio measurement, special units are used to indicate a weighted measure ...

in a sound level meter, to arrive at readings of loudness in phons or in decibels (dB) above the threshold of hearing (see A-weighting).

Weighting curves in electronic engineering, audio, and broadcasting

Although A-weighting with a slow RMS detector, as commonly used in sound level meters is frequently used when measuring noise in audio circuits, a different weighting curve, ITU-R 468 noise weighting uses a psophometric weighting curve and a quasi-peak detector. This method, formerly known as CCIR weighting, is preferred by the telecommunications industry, broadcasters, and some equipment manufacturers as it reflects more accurately the audibility of pops and short bursts of random noise as opposed to pure tones.

Psophometric weighting Psophometric weighting (from : psóphos "noise") 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 ...

is used in

telephony Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunications services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is ...

and

telecommunications Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

where narrow-band circuits are common. Hearing weighting curves are also used for sound in water.

Other applications of weighting

Acoustics is by no means the only subject which finds use for weighting curves however, and they are widely used in deriving measures of effect for sun exposure, gamma radiation exposure, and many other things. In the measurement of

gamma rays A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

or other ionising radiation, a radiation monitor or

dosimeter A radiation dosimeter is a device that measures the equivalent dose, dose uptake of external ionizing radiation. It is worn by the person being monitored when used as a personal dosimeter, and is a record of the radiation dose received. Modern el ...

will commonly use a filter to attenuate those energy levels or wavelengths that cause the least damage to the human body, while letting through those that do the most damage, so that any source of radiation may be measured in terms of its true danger rather than just its "strength". The

sievert The sievert (symbol: SvPlease note there are two non-SI units that use the same Sv abbreviation: the sverdrup and svedberg.) is a derived unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizin ...

is a unit of weighted radiation dose for ionising radiation, which supersedes the older weighted unit the rem ( roentgen equivalent man). Weighting is also applied to the measurement of sunlight when assessing the risk of skin damage through

sunburn Sunburn is a form of radiation burn that affects living tissue, such as skin, that results from an overexposure to ultraviolet (UV) radiation, usually from the Sun. Common symptoms in humans and other animals include red or reddish skin tha ...

, since different wavelengths have different biological effects. Common examples are the SPF of sunscreen, and the ultraviolet index. Another use of weighting is in television, where the red, green, and blue components of the signal are weighted according to their perceived brightness. This ensures compatibility with black-and-white receivers, and also benefits noise performance and allows separation into meaningful

luminance Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls wit ...

and chrominance signals for transmission.

References

{{Reflist, refs= IEC 61672, which has superseded IEC 60651, IEC 651, and earlier standards IEC 60268-1 {{cite journal , author-last1=Southall , author-first1=B. L. , author-last2=Bowles , author-first2=A. E. , author-last3=Ellison , author-first3=W. T. , author-last4=Finneran , author-first4=J. J. , author-last5=Gentry , author-first5=R. L. , author-last6=Greene , author-first6=C. R. , author-last7=Tyack , author-first7=P. L. , display-authors=etal , date=2007 , title=Overview , journal=Aquatic Mammals , volume=33 , number=4 , pages=411–414, doi=10.1578/AM.33.4.2007.411, bibcode=2007AqMam..33..411S Audio engineering Noise Sound

Weighting curves in electronic engineering, audio, and broadcasting

Other applications of weighting

See also

References