<P> An audio signal of very low level (with respect to the bit depth of the ADC) sampled without dither sounds extremely distorted and unpleasant . Without dither the low level may cause the least significant bit to "stick" at 0 or 1 . With dithering, the true level of the audio may be calculated by averaging the actual quantized sample with a series of other samples (the dither) that are recorded over time . A virtually identical process, also called dither or dithering, is often used when quantizing photographic images to a fewer number of bits per pixel--the image becomes noisier but to the eye looks far more realistic than the quantized image, which otherwise becomes banded . This analogous process may help to visualize the effect of dither on an analogue audio signal that is converted to digital . Dithering is also used in integrating systems such as electricity meters . Since the values are added together, the dithering produces results that are more exact than the LSB of the analog - to - digital converter . Note that dither can only increase the resolution of a sampler, it cannot improve the linearity, and thus accuracy does not necessarily improve . </P> <P> An ADC has several sources of errors . Quantization error and (assuming the ADC is intended to be linear) non-linearity are intrinsic to any analog - to - digital conversion . These errors are measured in a unit called the least significant bit (LSB). In the above example of an eight - bit ADC, an error of one LSB is 1 / 256 of the full signal range, or about 0.4% . </P> <P> All ADCs suffer from non-linearity errors caused by their physical imperfections, causing their output to deviate from a linear function (or some other function, in the case of a deliberately non-linear ADC) of their input . These errors can sometimes be mitigated by calibration, or prevented by testing . Important parameters for linearity are integral non-linearity (INL) and differential non-linearity (DNL). These non-linearities reduce the dynamic range of the signals that can be digitized by the ADC, also reducing the effective resolution of the ADC . </P> <P> When digitizing a sine wave x (t) = A sin ⁡ (2 π f 0 t) (\ displaystyle x (t) = A \ sin ((2 \ pi f_ (0) t))), the use of a non-ideal sampling clock will result in some uncertainty in when samples are recorded . Provided that the actual sampling time uncertainty due to the clock jitter is Δ t (\ displaystyle \ Delta t), the error caused by this phenomenon can be estimated as E a p ≤ x ′ (t) Δ t ≤ 2 A π f 0 Δ t (\ displaystyle E_ (ap) \ leq x' (t) \ Delta t \ leq 2A \ pi f_ (0) \ Delta t). This will result in additional recorded noise that will reduce the effective number of bits (ENOB) below that predicted by quantization error alone . The error is zero for DC, small at low frequencies, but significant when high frequencies have high amplitudes . This effect can be ignored if it is drowned out by the quantizing error . Jitter requirements can be calculated using the following formula: Δ t <1 2 q π f 0 (\ displaystyle \ Delta t <(\ frac (1) (2 ^ (q) \ pi f_ (0)))), where q is the number of ADC bits . </P>

How to convert from analog to digital signal