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Spectra
C H A P T E R
6 :
T E L E P H O N Y
T E S T I N G
Figure 6.11 shows the signal select wizard step for the spectra diagrams.
Select the spectra of the reference signal, the test signal or the difference
between the reference spectrum and the test spectrum.
Available result styles for the spectra (see Figure 6.12) are a linear frequency
scale or a Bark scale (as outlined in P.861). The Y-axis is always scaled in dB
SPL. Note that the Y-axis is depending on the setting of the listening level as set
by the algorithm properties dialog. The spectral resolution is dependent on the
sample rate of the input signals. At an input sample rate of 8kHz, a 256 point
FFT is used with a Hann window and 50% overlap to compute these data (as
required by P.861).
Figure 6.11: Select Signal Dialog
B A N D
V O I C E
Q U A L I T Y
128
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