Acoustic Tube Interpolation for Spectral Envelope Estimation in Artificial Bandwidth Extension

Abstract:
For historical reasons, today’s telephony frequencies are mostly still restricted to a narrowband of 3.4 kHz. Meanwhile wideband speech coding, also called HD voice, with a bandwidth of 7 kHz, is increasingly on the move into the networks and terminals. In the transition phase quite often a wideband terminal is receiving a narrowband signal. In order to achieve speech quality as close as possible to HD voice, artificial bandwidth extension (ABWE) has been developed as add-on for wideband equipment. State-of-the-art ABWE algorithms estimate and reconstruct missing frequency components with the help of the source-filter model of speech production. In this paper, a new method for estimating the model filter is presented, which is based on geometrical interpolation of the well known acoustical lossless tube model of speech production. Objective evaluation and subjective listening tests prove similar or even better quality compared to traditional more complex approaches.