Sonnox Oxford Limiter User Manual
Page 24
9.3 NoiseShapingDepthControl
9 DITHER AND NOISE SHAPING
• Increased audibility (unmasking) of various errors that may occur in play-out systems
Generally speaking, high levels of noise shaping render a signal that is more fragile.
Almost any change to the produced audio file after noise shaping could potentially result
in unwanted effects.
For these reasons the
DEPTH selector is provided to put you in charge of the degree to
which noise shaping is applied. When any of the noise shape curves are selected, the
depth selector varies the degree of noise shaping from 0% to 100% in 10% steps. At 0%
the dither is conventional HP TPDF dither (as if noise shaping were not selected), at 100%
full noise shaping is applied. All control positions within the range produce legal
proportions of dither.
The action of the depth control is illustrated below with
TYPE 1 selected:
There is no technical (or philosophical) advantage to noise shaping above and beyond
that which can be actually heard directly. Therefore the decision to use noise shaping
(and to what extent) is basically determined by what might actually be heard in practice. If
conventional TPDF dither provides sufficient audible dynamic range such that noise never
intrudes within the programme material, it is safest to avoid noise-shaping
altogether.
Because of the potential fragility of a noise shaped signal, it is better to ensure that it is
carried out only at the finalstages of mastering, immediately prior to release. If your mix is
not already a final master, it is technically preferable to send a TPDF dithered 24-bit file to
the mastering facility rather than a 16-bit noise shaped file.
Another important factor is that the effectiveness of psycho-acoustic noise shaping relies
heavily on our sensitivity to noise spectra at the thresholdofhearing. Therefore, if noise