Mobile phones as well as tablets are omnipresent and belong to everyday
life. Today audiovisual communication takes place at different locations
and in a large variety of acoustic environments. In consequence, the
intelligibility as well as the quality of speech may significantly be
degraded by ambient background noise. In order to improve speech
intelligibility and to ensure a convenient communication with high audio
quality, speech enhancement techniques are required. In this thesis all
critical components contributing to the enhancement of the up-link
signal are addressed:
• signal capturing at the acoustic front-end with a
new near field beamformer,
• new codebook based speech and noise
estimation procedure generating and exploiting reliability information,
and
• actual noise reduction exploiting spectral dependencies of human
speech.
For the acoustic front-end of the digital processing chain a
novel concept for the filter optimization of a near field beamformer is
introduced. The optimization scheme allows to closely approximate a
predefined reception characteristic which can be freely chosen according
to the application. The output of the beamformer provides a
pre-enhanced signal with improved SNR for subsequent single-microphone
based speech enhancement.
