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Signal Processing (SP)
Department of InformaticsSignal Processing (SP)

Photo: Timo Gerkmann/SP

Signal Processing

Nonlinear spatial filtering in multichannel speech enhancement

This website accompanies the journal paper
Kristina Tesch, Timo Gerkmann, "Nonlinear Spatial Filtering in Multichannel Speech Enhancement", IEEE/ACM Trans. Audio, Speech, Language Proc., Vol. 29, pp. 1795-1805, 2021. [doi] [arxiv] [pdf]. ITG VDE award 2022

The sound examples on this website demonstrate the performane advantage of a joint spatial-spectral nonlinear filter TMMSE in comparison with the classical combination of a linear beamformer and a spectral postfilter, referred to as TMVDR-MMSE. We provide sound examples for the following experimental settings:

  • (Section V) An inhomogeneous noise field created by five directional sources emitting non-overlapping Gaussian signals
  • (Section IV-B) An inhomogeneous noise field created by five interfering human speakers
  • (Section IV-C) Real-world noise data from the CHiME3 database
  • (Section IV-A) Noise sampled from a Gaussian mixture distribution with varying heavy-tailedness

V. Interpretation: a nonlinear spatial filter enables superior spatial selectivity

The experimental setup is illustrated by the figure on the right. A target speech source is placed in broadside direction of the two-dimensional microphone array and five directional interfering sources are positioned as indicated by the black boxes. Here we use non-overlapping Gaussian bursts as interfering signals.

IV-B. Inhomogeneous noise field (interfering speech)

Clean Noisy TMMSE (proposed) TMVDR-MMSE TMVDR
Example 1
Example 2
Example 3
Example 4

IV-C. Real-world CHiME3 noise

The differences between the proposed spatially nonlinear TMMSE and the classical combination of a linear beamformer TMVDR-MMSE are most obvious for directed impulsive noise as the clattering of dishes in the cafeteria noise examples.

Clean Noisy TMMSE (proposed) TMVDR-MMSE TMVDR
Example 1 (CAF)
Example 2 (CAF)
Example 3 (PED)
Example 4 (PED)

IV-A. Heavy-tailed noise distribution

Example Clean Noisy TMMSE (proposed) TMVDR-MMSE TMWF TMVDR
Kurtosis factor q ≈ 8 (female)
Kurtosis factor q ≈ 8 (male)
Kurtosis factor q ≈ 4 (female)
Kurtosis factor q ≈ 4 (male)