Europe, and former countries of the British Empire such as Australia and South Africa. Though the noise level of 16-bit audio systems (such as CD players) is commonly quoted (on the basis of calculations that take no account of subjective effect) as −96 dB relative to FS (full scale), the best 468-weighted results are in the region of −68 dB relative to Alignment Level (commonly defined as 18 dB below FS) i.e. −86 dB relative to FS. The use of weighting curves is in no way to be regarded as 'cheating', provided that the proper curve is used. Nothing of relevance is being 'hidden', and even when, for example, hum is present at 50 or 100 Hz at a level above the quoted (weighted) noise floor this is of no importance because our ears are very insensitive to low frequencies at low levels, so it will not be heard. A-weighting is often used to compare and qualify ADCs, for instance, because it more accurately represents the way noise shaping hides dither noise in the ultrasonic range. Other applications of weighting In the measurement of gamma rays or other ionising radiation, a radiation monitor or dosimeter 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 is a unit of weighted radiation dose for ionising radiation, which supersedes the older unit the REM (roentgen equivalent man). Weighting is also applied to the measurement of sunlight when assessing the risk of skin damage through sunburn, since different wavelengths have different biological effects. Common examples are the SPF of sunscreen, and the UV 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 and chrominance signals for transmission. See also Weighting Weighting curve Sone Phon ITU-R 468 noise weighting Psophometric weighting Equal-loudness contour Noise pollution Noise regulation A-weighting B-weighting C-weighting D-weighting G-weighting M-weighting Z-weighting Notes References External links Noise measurement briefing Calculator for A,C,U, and AU weighting values A-weighting filter circuit for audio measurements AES pro audio