Specifications

2.23
Applications Manual
© 2003-2005 Prism Media Products Ltd
Revision 1.11Prism Sound dScope Series III
3.2.7.1 Idle channel noise
Applies to:
EUTs with analogue or digital inputs and analogue or digital outputs.
Aim:
To measure the output noise of the
EUT
with no signal present.
Method
If the EUT has a digital input, it is fed with a digital-zero signal; if the EUT has an analogue input it is
terminated with 50R (or 25R if unbalanced).
The RMS amplitude of the output noise of the EUT is measured via the
standard weighting filter
. The
result is reported for both channels, in
dBFS
(in the case of an analogue measurement, this is
equivalent to dB below the specified
D/A line-up
), and designated as 'dBFS CCIR-RMS'.
3.2.7.2 Idle channel noise spectrum
Applies to:
EUTs with analogue or digital inputs and analogue or digital outputs.
Aim:
To measure the output noise spectrum of the
EUT
with no signal present.
Method
If the EUT has a digital input, it is fed with a digital-zero signal; if the EUT has an analogue input it is
terminated with 50R (or 25R if unbalanced).
The RMS amplitude of the output noise of the EUT is measured via the
standard weighting filter
in a
range of 1/3 octave bands between 20Hz and the
upper band-edge frequency
. The result is graphed
for each channel in
dBFS
(in the case of an analogue measurement, this is equivalent to dB below the
specified
D/A line-up
).
3.2.7.3 Signal-to-noise ratio or noise in the presence of signal
Applies to:
EUTs with analogue or digital inputs and analogue or digital outputs.
Aim:
To measure the output noise of the
EUT
in the presence of signal.
Method
The EUT is fed with a 997Hz sinusoidal stimulus at an amplitude 60dB below its maximum signal
amplitude (–60
dBFS
).
The output of the EUT is passed through a
standard notch filter
at the frequency of the stimulus, and
also through the
standard weighting filter
.
The RMS amplitude of the residual is measured
for both
channels, in
dBFS
(in the case of an analogue measurement, this is equivalent to dB below the
specified
D/A line-up
), and designated as 'dBFS CCIR-RMS'.
See also:
Level Search Routines
for fault finding with this test.