Specifications
2.22
Applications Manual
© 2003-2005 Prism Media Products Ltd
Revision 1.11Prism Sound dScope Series III
3.2.6.5.1 Total harmonic distortion and noise vs frequency
Applies to:
EUTs with analogue or digital inputs and analogue or digital outputs.
Aim:
To measure the THD+N of the
EUT
against frequency.
Method
A –1
dBFS
sinusoidal stimulus is applied to the EUT, successively at each octave frequency between
20Hz and half the
upper band-edge frequency
. The output of the EUT is passed through a
standard notch filter
at the frequency of the stimulus, and also through a low-pass filter at the upper
band-edge frequency (or at 20kHz, whichever is the lower). The RMS amplitude of the residual is
measured for each stimulus frequency.
The results are presented graphically, with THD+N (in % relative to the amplitude of the stimulus)
being plotted for each channel against stimulus frequency.
The test is then repeated with a stimulus amplitude of –20dBFS, the results being overlaid on the
original graph.
3.2.6.5.2 Total harmonic distortion and noise vs level
Applies to:
EUTs with analogue or digital inputs and analogue or digital outputs.
Aim:
To measure the THD+N of the
EUT
against amplitude.
Method
A 997Hz sinusoidal stimulus is applied to the EUT, successively at a range of amplitudes 10dB apart
between 0
dBFS
and –80dBFS. The output of the EUT is passed through a
standard notch filter
at the
frequency of the stimulus, and also through a low-pass filter at the
upper band-edge frequency
(or at
22kHz, whichever is the lower). The RMS amplitude of the residual is measured for each stimulus
amplitude.
The results are presented graphically, with THD+N (in %, relative to the amplitude of the stimulus)
being plotted for each channel against stimulus amplitude.
3.2.7 Signal-to-noise
The Signal-to-noise tests are arranged in the following subsections, which correspond to the
equivalent subsections of the AES17 standard:
Idle channel noise
Idle channel noise spectrum
Signal-to-noise ratio or noise in the presence of signal
Power-line (mains) related products