Shift in Speech Quality and Acceptability Level between 2008-2012

Although listening quality measurement is well standardized the MOS scale may be to fine and not so easy for interpretation of results, for example for mobile operators. Therefore we thought that in some cases mapping to acceptability scale with less points would be more useful and we tried to find how to map these two scales on each other. For our purposes we used three points scale. We had an opportunity to carry out same test three times with similar group of listeners and therefore we were able to find whether there was actually systematic shift in our results between these test sessions, which took place with two years span. It was already proven that perceived quality varies with listener’s age in Holub and Šmíd & Bachtík (2003). But test performed by authors was performed at the same test session with listeners of different age. Moreover we focused on comparing shift in listening quality and acceptability level. On first sight it could seems reasonable that the shift should be same or at least very similar. We will also investigate whether this supposed shift is same through all tested conditions or if it differs depending on used coders and background noise.