Parameters Impact on Speech Quality

To illustrate the impact of the considered parameters (Codec, LR, CLP and PI) on speech quality, we have drawn a set of 3D Figures and a bar-graph. To generate the data necessary to draw these Figures, we used an RNN trained and tested by the ``Spanish'' quality databases described and evaluated in Chapter 5. We did the same tests using the ``Arabic'' databases, but the results were approximately the same, therefore, we omitted the resulting Figures as they will not provide further useful information concerning our study here. For all the figures shown in Figure7.1, on the left-hand side, we show the variation of the quality as a function of LR and CLP for the different codecs and for PI=20ms. In this Figure but on the right-hand side, we show the variation of the quality as a function of LR and PI for the different codecs and CLP=1. In Figure 7.2 on the left-hand side, we show the variation of the quality as a function of CLP and PI at LR=5 %. On the right-hand side we do the same but for LR=10 %. Note that the Z-axis scale is the same for each pair of Figures. We show also in Figure 7.3 the variation of the quality as a function of LR and the different codecs for PI=20ms and CLP=2. In the next subsections, we study the effect of each parameter to the quality.