Browse all publications by topic
Browse all publications by year
- I. Schwetz, G. Gruhler,
and K. Obermayer. Stationarity of Speech Radiation: consequences for
Linear Multichannel Filtering.
.
IEEE Trans. Speech Audio Proc., 12:460-467, 2004.
(FTP PDF, 881 kb)
Speech processing using multichannel microphone systems is often
based on slowly adapting, linear filters. These systems are able to extract a
single source from a mixture (and suppress the others)-if the speech
radiation can be described by a linear and time-invariant transfer function.
Here, we test this assumption using a two-channel microphone array and a
human talker as the speech source. We measure correlations between the
signals received by the two microphones for individual phonemes using the
magnitude squared coherence. Stationarity is addressed by comparing optimal
filters between different phoneme pairs using the system distance. We find
that, in particular for fricatives, the coherence of the speech signals
radiated to different directions is very low. We also find, that the transfer
functions from the mouth to the microphones differ significantly between
vowels, depending on the locations of the two microphones. These measurements
show that the general mixing model does not hold for speech for arbitrary
microphone setups, and that multichannel microphone systems have to be
carefully designed.
|
