<Dl> <Dt> Rumble </Dt> <Dd> The measure of the low frequency (many tens of Hz) noise contributed by the turntable of an analogue playback system . It is caused by imperfect bearings, uneven motor windings, vibrations in driving bands in some turntables, room vibrations (e.g., from traffic) that is transmitted by the turntable mounting and so to the phono cartridge . A lower number is better . </Dd> </Dl> <Dd> The measure of the low frequency (many tens of Hz) noise contributed by the turntable of an analogue playback system . It is caused by imperfect bearings, uneven motor windings, vibrations in driving bands in some turntables, room vibrations (e.g., from traffic) that is transmitted by the turntable mounting and so to the phono cartridge . A lower number is better . </Dd> <P> Note that digital systems do not suffer from many of these effects at a signal level, though the same processes occur in the circuitry, since the data being handled is symbolic . As long as the symbol survives the transfer between components, and can be perfectly regenerated (e.g., by pulse shaping techniques) the data itself is perfectly maintained . The data is typically buffered in a memory, and is clocked out by a very precise crystal oscillator . The data usually does not degenerate as it passes through many stages, because each stage regenerates new symbols for transmission . </P> <P> Digital systems have their own problems . Digitizing adds noise, which is measurable and depends on the audio bit depth of the system, regardless of other quality issues . Timing errors in sampling clocks (jitter) result in non-linear distortion (FM modulation) of the signal . One quality measurement for a digital system (Bit Error Rate) relates to the probability of an error in transmission or reception . Other metrics on the quality of the system are defined by the sample rate and bit depth . In general, digital systems are much less prone to error than analog systems; However, nearly all digital systems have analog inputs and / or outputs, and certainly all of those that interact with the analog world do so . These analog components of the digital system can suffer analog effects and potentially compromise the integrity of a well designed digital system . </P>

16. which one of the following parameter is not useful for comparing noise performance of receiver