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C H A P T E R
5 :
W I D E
B A N D
A U D I O
Q U A L I T Y
T E S T I N G
Figure 5.19: Signal Select window of the Masked Threshold
Figure 5.20: The Masked Threshold diagram
Loudness
The perceived loudness of audio signals depends on their frequency, their
duration and their sound pressure level. Due to auto-masking the loudness of a
complex signal is less than the sum of the loudness of all its components. In the
context of audio quality measurement, the loudness of the unwanted distortion
added to the reference signal, the noise loudness, is reduced by the partial
masking caused by the reference signal [ITUR1387].
A choice can be made between the loudness of the reference signal and the
loudness of the test signal (see Figure 5.21). As Figure 5.22Figure 5.22
shows, the scaling of the vertical axis is Sone, the horizontal axis may be scaled
in Bark or in Herz. The resulting view looks as Figure 5.23
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