Subband modulation analysis, processing and synthesis

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The decomposition (analysis) of audio signals into perceptually meaningful multiband modulation components opens up new possibilities for advanced signal processing in the fields of studio audio effects, audio compression and hearing aids technology. Our signal adaptive analysis approach provides a powerful handle on the perceptual properties of the signal: pitch, timbre or roughness can be manipulated straight forward. Additionally we specify a synthesis method providing high subjective perceptual quality.

The task of decomposing a wide-band audio signal into a set of components each comprising carrier, amplitude modulation, and frequency modulation is an ill-defined problem with an infinite number of solutions. Thus we pose the constraint of the modulation decomposition being straight forward interpretable and perceptually meaningful in a sense that modulation processing applied on the modulation information should produce perceptually smooth results avoiding undesired artefacts introduced by the limitations of the modulation representation itself which is an inevitable problem if static filterbanks are used. Thus our decomposition approach is designed to be signal adaptive.

Firstly, the fullband signal is partitioned into spectral subbands by an adaptive set of band pass filters having local spectral centers of gravity as center frequencies rather than utilizing a static filter bank. Each (analytic) band pass signal is further decomposed into magnitude and instantaneous frequency yielding the desired amplitude modulation (AM) and frequency modulation (FM). After modulation processing has been applied, additive synthesis is accomplished by a bank of amplitude and frequency modulated oscillators.


A poster illustrating two exemplary use cases of AM/FM domain audio signal processing

  • AM/FM processing for coding applications
  • Carrier frequency processing for transposing/key mode change
can be viewed here: modulation_poster (file size 800 kB)

Slides and accompanying audio samples (as presented at DAFx 2008)

DAFx 2008 Slides and accompanying audio samples can be downloaded at the DAFx08 site.

Slides containing audio samples (as presented at ICASSP 2009)

DAFx 2008 Slides containing audio samples can be vied here (file size 16 MB).

Show all publications
  • Tom Bäckström, Sascha Disch
    Parametric AM/FM Decomposition for Speech and Audio Coding
    Proc. of IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA'09), October 2009
  • Sascha Disch, Bernd Edler
    An iterative segmentation algorithm for audio signal spectra depending on estimated local centers of gravity
    12th International Conference on Digital Audio Effects (DAFx-09), September 2009
  • Sascha Disch, Bernd Edler
    Multiband perceptual modulation analysis, processing and synthesis of audio signals
    ICASSP International Conference on Acoustics, Speech and Signal Processing , IEEE CNF, Taipei, Taiwan, April 2009