Improved Artificial Low-pass Extension of Telephone Speech

In this contribution a new method for artificial bandwidth extension of telephone speech towards frequencies below 300 Hz is proposed. The method defines a self-contained module which can be applied to any artificial bandwidth extension system, designed for extending the bandwidth only to frequencies above the telephone-band. At this, the amplification of a separate ARMA filter with a pass-band characteristic below the telephone-band is adapted such that the spectral tilt is continued to the frequencies below the telephone-band. In comparison with traditional artificial extension systems based on codebook approaches the new method produces less roughness and rattling background noise in the synthesized signal.