Withopf, Jochen; Schmidt, Gerhard (Christian-Albrechts-Universität zu Kiel, Kaiserstr. 2, 24143 Kiel, Germany)
Hannon, Patrick; Krini, Mohamed (SVOX Deutschland GmbH, Magirus-Deutz-Str. 16, 89077 Ulm, Germany)
The majority of current speech enhancement systems are based on generalized signal-to-noise ratio dependent weighting rules and do not take into account the characteristics of the actual speech sound being processed. The following contribution is concerned with phoneme-specific speech enhancement methods that apply specially tailored signal processing methods. The first signal processing algorithm proposed in this work - fricative spreading - enhances high frequency unvoiced sounds for bandlimited speech transmission. The spreading algorithm detects different fricatives using a vector quantization codebook and then a suitable spectral compression function is applied to map high frequency energy from above the transmission bandwidth threshold into lower frequency regions still within the transmission bandwidth. A second approach - formant boosting - provides enhancement for voiced speech. Utilizing the codebook classification from fricative spreading, voiced speech phonemes are identified and accentuated by boosting formant regions and attenuating in between the formant frequencies.