A noise weighting is a specific amplitude-vs.-

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

characteristic that is designed to allow subjectively valid measurement of noise. It emphasises the parts of the spectrum that are most important. Usually, noise means audible noise, in audio systems, broadcast systems or telephone circuits. In this case the

weighting The process of weighting involves emphasizing the contribution of particular aspects of a phenomenon (or of a set of data) over others to an outcome or result; thereby highlighting those aspects in comparison to others in the analysis. That i ...

is sometimes referred to as

Psophometric weighting Psophometric 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 ...

, though this term is best avoided because, although strictly a general term, the word Psophometric is sometimes assumed to refer to a particular weighting used in telecommunications. A major use of noise weighting is in the measurement of residual noise in

audio equipment Audio equipment refers to devices that reproduce, record, or process sound. This includes microphones, radio receivers, AV receivers, CD players, tape recorders, amplifiers, mixing consoles, effects units, headphones, and Speaker (audio equipmen ...

, usually present as hiss or hum in quiet moments of programme material. The purpose of weighting here is to emphasise the parts of the audible spectrum that our ears perceive most readily, and attenuate the parts that contribute less to our perception of loudness, in order to get a measured figure that correlates well with subjective effect. The

ITU-R 468 noise weighting ITU-R 468 (originally defined in CCIR recommendation 468-4, therefore formerly also known as CCIR weighting; sometimes referred to as CCIR-1k) is a standard relating to noise measurement, widely used when measuring noise in audio systems. The ...

was devised specifically for this purpose, and is widely used in broadcasting, especially in the UK and Europe.

A-weighting A-weighting is the most commonly used of a family of curves defined in the International standard IEC 61672:2003 and various national standards relating to the measurement of sound pressure level. A-weighting is applied to instrument-measured ...

is also used, especially in the United States, though this is only really valid for the measurement of tones, not noise, and is widely incorporated into sound level meters. In

telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...

, noise weightings are used by agencies concerned with public telephone service, and various standard curves are based on the characteristics of specific commercial

telephone A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into e ...

instruments, representing successive stages of technological development. The coding of commercial apparatus appears in the nomenclature of certain weightings. The same weighting nomenclature and units are used in military versions of commercial noise measuring sets. Telecommunication measurements are made in lines terminated either by the measuring set or an instrument of the relevant class.

References

Noise Audio engineering Sound Acoustics {{acoustics-stub

See also

References