Sonnox Oxford Limiter User Manual
Page 20
9.1 ConventionalDither
9 DITHER AND NOISE SHAPING
As it can be seen, all the harmonic errors have been removed. Also, since the FFT analysis
method provides an enhanced view of the signal below the noise floor, it can also be seen
that there is effectively no low level floor below which a signal will fail to pass.
The graph below illustrates this fact by showing a 1KHz signal at —120dBr passing
through a dithered 16-bit system. This corresponds to a signal 24dB below the level of
the least significant bit; the effective channel SNR (Signal to Noise Ratio) is added in blue
for illustration purposes.
This illustrates that dither turns a quantised numerical signal conduit into the equivalent of
a naturally continuous (un-quantised) system, which exhibits a finite signal to noise ratio
with
nopracticallimit to harmonic signal resolution. In other words the inescapable
presence of quantisation in numerical systems
doesnot forcibly lead to ‘discontinuity’ or
‘resolution loss’ in the signal. The misunderstanding of this fact underpins many of the
most damaging misconceptions surrounding digital audio systems. It can also be
deduced from the above graphs that any undithered digital representation of an audio
signal is effectively illegal.