Table 11 - Dither And Noise Shaping Noise Powers - DCS 905 User Manual

dCS 905 User Manual
dCS Ltd
9
16 bit Q noise is -98.1dB relative to a full scale sine wave.
10
DSD carries this further. The principle is the same, but with DSD, there is more noise than there is signal,
even at full scale. It is just that it is in a part of the spectrum the ear cannot hear.
Manual filename: dCS905 Manual v1.0x Eng.doc
English version
possibly get away with – the amount that simple 16 bit truncation (16 bit Q
noise) would give, if it were well behaved, which it is not.
Truncation Type, with
44.1 kS/s data rate
16 bit truncation
16 bit truncation with
Top Hat dither
16 bit truncation with
Triangular dither
16 bit truncation with
Noise Shaped
Triangular dither
16 bit truncation with 3
order noise shaping and
no dither
16 bit truncation with 3
order noise shaping and
Noise Shaped
Triangular dither
16 bit truncation with 9
order noise shaping and
no dither
16 bit truncation with 9
order noise shaping and
Noise Shaped
Triangular dither
Table 11 – Dither and Noise Shaping Noise Powers
Straight forward dither always adds noise – it can only produce signals with a
noise floor higher than Q noise on its own. However, the noise power added is
a few dBs for simple types. Noise shaping adds rather more noise, but it can be
made to add it in parts of the spectrum that the ear is less sensitive to, so the
perceived noise (F weighted noise) is lower – up to three bits lower. It results in
a signal that the ear hears as having a far lower noise floor than a 16 bit
truncated signal, rather than the "not much worse" of dither alone, even though
there is really more noise present
Noise,
unweighted,
F weighted,
rel 16 bit Q
rel 16 bit Q
9
noise
0dB
3dB
4.8dB
4.8dB
rd
6.9dB
rd
11.0dB
th
23.4dB
th
28.2dB
10
.
Page 63
Manual for Software Issue 1.0x
November 2006
Noise, Comments
noise
0dB Unpleasant low
level effects
3dB Okay – can show
noise modulation at
low signal levels
4.8dB
modulation and
unpleasant effects
removed, but noise
floor is high
1.2dB
modulation and
unpleasant effects
removed. Not much
perceived noise
-10.5dB Okay with input
noise floors down
Unconditionally free
-9.2dB
from truncation
effects with all
-17.9dB Okay with input
noise floors down
-16.7dB Unconditionally free
from truncation
effects with all
email: more@dcsltd.co.uk
web-site: www.dcsltd.co.uk
All noise
All noise
penalty
to –102dB
inputs
to –120dB
inputs