Bandwidth Extension of Speech Signals
Peter Vary, Rainer Martin · 2023
The characteristic sound of telephone speech with its restricted audio quality goes back to the frequency bandwidth limitation of the old analog narrowband (NB) telephone. Due to the progress of the digital signal processing technology, speech codecs for the so-called wideband (WB) telephony have been standardized with a bandwidth of B = 7kHz and a sampling rate of f s = 16 kHz. The attractiveness of new WB services and devices would be increased, if the received NB speech signal could be improved by means of bandwidth extension (BWE). This chapter discusses two BWE concepts on the basis of the source-filter model of speech production. It explains basic BWE concepts with and without side information for the extension of high frequencies. These methods may also be used for the extension of low frequencies.