This chapter deals with the evaluation of the quality produced by the different approaches for the tasks of extending the excitation signal and estimating the broadband spectral envelope. All in all we can differentiate between objective and subjective criteria. The objective quality criteria that have been used within this book have been introduced in Sect. 3.4. The subjective evaluation is done by subjects listening to the various approaches followed by a voting for the different approaches. This can be done in miscellaneous fashions. The specific method used for the subjective quality evaluation will be discussed within the respective sections. The examination of subjective quality evaluation will close with a significance analysis. At the end of the evaluation of each component for extending the bandwidth of a bandlimited speech signal the analysis of the rank correlation between the objective and subjective quality criteria will give information on the usability of the various objective quality criteria respectively the usability of objective quality criteria in general. A very popular speech quality measure (PESQ; Perceptual Evaluation of Speech Quality [ITU 01]) that tries to simulate a subjective listening test has been examined but has been discarded since it gave no reasonable results, which is due to the different kind of scenario it was designed for. Other examinations can be found in [Kallio 02].
KeywordsSpeech Signal Spectral Shift Excitation Signal Listening Test Spectral Envelope
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