A-weighting

A-weighting is a form of <a href="/facts/Weighting/HUltmeDW">frequency weighting</a> and the most commonly used of a <a href="/facts/Weighting_filter/CM88XjPC">family of curves</a> defined in the International standard <a href="/facts/International_Electrotechnical_Commission/hSK0kjwI">IEC</a> 61672:2003 and various national standards relating to the measurement of <a href="/facts/Sound_pressure_level/MgJAcp2I">sound pressure level</a>. A-weighting is applied to instrument-measured sound levels in an effort to account for the relative <a href="/facts/Loudness/N760pyRc">loudness</a> perceived by the human ear, as the ear is less sensitive to low audio frequencies. It is employed by arithmetically adding a table of values, listed by <a href="/facts/Octave_band/NNaXyR63">octave</a> or third-octave bands, to the measured sound pressure levels in <a href="/facts/Decibel/0LyxAPXh">dB</a>. The resulting octave band measurements are usually added (logarithmic method) to provide a single A-weighted value describing the sound; the units are written as dB(A). Other weighting sets of values – B, C, D and now Z – are discussed below.
The curves were originally defined for use at different average sound levels, but A-weighting, though originally intended only for the measurement of low-level sounds (around 40 <a href="/facts/Phon/7gPf87lq">phon</a>), is now commonly used for the measurement of <a href="/facts/Environmental_noise/CdNaQ5kb">environmental noise</a> and <a href="/facts/Industrial_noise/XvGV55cl">industrial noise</a>, as well as when assessing potential <a href="/facts/Noise-induced_hearing_loss/3fvhFuDv">hearing damage</a> and other <a href="/facts/Noise_health_effects/6A2Fz81a">noise health effects</a> at all sound levels; indeed, the use of A-frequency-weighting is now mandated for all these measurements, because decades of field experience have shown a good correlation with occupational deafness in the frequency range of human speech. It is also used when measuring low-level noise in audio equipment, especially in the United States.[not verified in body] In Britain, Europe and other parts of the world, broadcasters and audio engineers[who?] more often use the <a href="/facts/ITU-R_468_noise_weighting/kMEdMoNM">ITU-R 468 noise weighting</a>, which was developed in the 1960s based on research by the <a href="/facts/BBC/qFateIz8">BBC</a> and other organizations. This research showed that our ears respond differently to random noise, and the equal-loudness curves on which the A, B and C weightings were based are really only valid for pure single tones.[not verified in body]

A-weighting open-in-new

A-weighting