INTERSPEECH 2007
8th Annual Conference of the International Speech Communication Association

Antwerp, Belgium
August 27-31, 2007

Reconstructing Audio Signals from Modified Non-Coherent Hilbert Envelopes

Joachim Thiemann, Peter Kabal

McGill University, Canada

In this paper, we present a speech and audio analysis-synthesis method based on a Basilar Membrane (BM) model. The audio signal is represented in this method by the Hilbert envelopes of the responses to complex gammatone filters uniformally spaced on a critical band scale. We show that for speech and audio signals, a perceptually equivalent signal can be reconstructed from the envelopes alone by an iterative procedure that estimates the associated carrier for the envelopes. The rate requirement of the envelope information is reduced by low-pass filtering and sampling, and it is shown that it is possible to recover a signal without audible distortion from the sampled envelopes. This may lead to improved perceptual coding methods.

Full Paper

Acoustic Examples

fspeech.wav Original unmodified speech sample
fspeech0.wav Original speech file bandpass filtered to match the system transfer function
fspeech1.wav Speech signal reconstructed from envelopes: first estimate using monochromatic carriers
fspeech2.wav Speech signal reconstructed from envelopes: final estimate after 200 iterations
fspeech3.wav Speech signal reconstructed from modified envelopes: envelopes for channels above 1500Hz sampled at 1.2 times their CBW.
fspeech4.wav  Speech signal reconstructed from modified envelopes: envelopes for channels above 1500Hz sampled at 1.2 times their CBW, below 1500Hz sampled at 250Hz.
organ0.wav Original music sample, bandpass filtered
organ1.wav Music sample reconstructed from envelopes: estimate after 200 iterations
organ2.wav Music sample reconstructed from envelopes: estimate after 1000 iterations
organ3.wav Music sample reconstructed from envelopes: estimate after 200 iterations using a higher density of envelope channels (4 per CB, 123 total)

Bibliographic reference.  Thiemann, Joachim / Kabal, Peter (2007): "Reconstructing audio signals from modified non-coherent hilbert envelopes", In INTERSPEECH-2007, 534-537.