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C H A P T E R
6 :
T E L E P H O N Y
T E S T I N G
x [n]
i
Hanning window
xw [n]
i
FFT
X [k]
i
Px [k]
i
frequency warping
Px [j]
'
i
filter with receiving
characteristics of
handset
PFx [j]
i
PHx [j]
i
intensity warping
Lx [j]
i
Figure 6.3: Block diagram of the PSQM Algorithm according to [ITUT861]
The following blocks are intended to represent the cognitive part of the
modelling. The "asymmetry processing" should take into account that
distortions, which were introduced by the device under test, are more easily
perceived than signal components that were left out by the codec. Finally, the
"silent interval weighting" will differ between silent and speech active intervals
over the time. It is believed that this parameter allows a fitting of the cognitive
processing to cultural differences. It was shown that almost identical subjective
tests carried out at several locations in the world, and comprising different
languages have led to different results, for instance in Europe, and Asia. It was
concluded that the difference
B A N D
V O I C E
calculate
local scaling
factor
Hoth noise
calculate
loudness
scaling factor
Cognitive
subtraction
N [j]
i
asymmetry processing
N
i
silent interval weighting
N
w sil
results from language differences, and the
122
Q U A L I T Y
y [n]
i
Hanning window
yw [n]
i
FFT
Y [k]
i
Py [k]
i
frequency warping
'
Py [j]
i
S
Py [j]
"
i
filter with receiving
characteristics of
handset
PFy [j]
i
PHy [j]
i
intensity warping
Ly [j]
i
Sl
i
Ly [j]
'
i
T1207950-96
i
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