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A graph of the A-, B-, C- and D-weightings across the frequency range 10 Hz – 20 kHz Video illustrating A-weighting by analyzing a sine sweep (contains audio). A-weighting is a form of frequency weighting and 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. [1]
The ITU-R 468 noise weighting was devised specifically for this purpose, and is widely used in broadcasting, especially in the UK and Europe. A-weighting is also used, especially in the United States, [1] [dubious – discuss] though this is only really valid for the measurement of tones, not noise, and is widely incorporated into sound level ...
A major use of noise weighting is in the measurement of residual noise in audio equipment, 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 ears perceive most readily, and attenuate the parts that contribute less to perception of loudness, in order to get a measured figure that correlates ...
The weighting curve is specified by both a circuit diagram of a weighting network and a table of amplitude responses. Above is the ITU-R 468 Weighting Filter Circuit Diagram. The source and sink impedances are both 600 ohms (resistive), as shown in the diagram. The values are taken directly from the ITU-R 468 specification.
The specification of weighted CCIR-468 quasi-peak noise, and weighted quasi-peak wow and flutter became particularly widely used and attempts were made to find more valid methods for distortion measurement. Measurements based on psychoacoustics, such as the measurement of noise, often use a weighting filter.
A commonly used weighting is the A-weighting curve, which results in units of dBA sound pressure level. Because the frequency response of human hearing varies with loudness, the A-weighting curve is correct only at a level of 40- phon and other curves known as B- , C- and D-weighting are also used, the latter being particularly intended for the ...
Frequency weighting: A-weighting or C-weighting Exponential averaging: F (fast); S (slow) Criterion level: 90, 85, 84, 80, or V (variable) Criterion duration: Hours Threshold level: 90, 80, or V (variable) Exchange rate: 5, 4, or 3 A noise or sound dose is the amount of sound a person is exposed to in a day. The dose is represented by a percentage.
Microphones, amplifiers and recording systems all add some electronic noise to the signals passing through them, generally described as hum, buzz or hiss. All buildings have low-level magnetic and electrostatic fields in and around them emanating from mains supply wiring, and these can induce hum into signal paths, typically 50 Hz or 60 Hz (depending on the country's electrical supply standard ...