A-Weighting - A form of electrical filter which is designed to mimic the relative sensitivity of the human ear to different frequencies at low sound pressure levels (notionally 40 Phons or about 30dBA SPL). Essentially, the filter rolls-off the low frequencies below about 700Hz and the highs above about 10kHz. This filtering is often used when making measurements of low-level sounds, like the noise floor of a device. (See also C-Weighting and K-Weighting)