  The throat microphone is a body-attached transducer that is worn against the
neck. It captures the signals that are transmitted through the vocal folds,
along with the buzz tone of the larynx. Due to its skin contact, it is more
robust to the environmental noise compared to the acoustic microphone that
picks up the vibrations through air pressure, and hence the all interventions.
The throat speech is partly intelligible, but gives unnatural and croaky sound.
This thesis tries to recover missing frequency bands of the throat speech and
investigates envelope and excitation mapping problem with joint analysis of
throat- and acoustic-microphone recordings. A new phone-dependent GMM-based
spectral envelope mapping scheme, which performs the minimum mean square error
(MMSE) estimation of the acoustic-microphone spectral envelope, has been
proposed. In the source-filter decomposition framework, we observed that the
spectral envelope difference of the excitation signals of throat- and
acoustic-microphone recordings is an important source of the degradation in the
throat-microphone voice quality. Thus, we also model spectral envelope
difference of the excitation signals as a spectral tilt vector, and propose a
new phone-dependent GMM-based spectral tilt mapping scheme to enhance throat
excitation signal. Experimental evaluations are performed to compare the
proposed mapping scheme using both objective and subjective evaluations.
Objective evaluations are performed with the log-spectral distortion (LSD) and
the wide-band perceptual evaluation of speech quality (PESQ) metrics.
Subjective evaluations are performed with A/B pair comparison listening test.
Both objective and subjective evaluations yield that the proposed
phone-dependent mapping consistently improves performances over the
state-of-the-art GMM estimators.

Audio and Speech Processing;Signal Processing