Extension spectrale d'un signal de parole de la bande t\'el\'ephonique \`a la bande AM

TL;DR

This paper presents a system for bandwidth extension of telephone speech signals to wideband using independent high and low-frequency methods, employing neural networks and sinusoidal models to improve sound quality.

Contribution

It introduces a novel bandwidth extension system combining excitation-filter and sinusoidal models with neural networks for spectral and amplitude estimation.

Findings

Sound quality after extension exceeds narrowband speech

Significant listener variation in perceived quality

Excitation extension techniques are promising for speech coding

Abstract

This document proposes a bandwidth extension system producing a wideband signal from a narrowband speech signal. The extension is performed independently for high and low frequencies. High-frequency extension uses the excitation-filter model. Extension of the excitation is performed in the time domain using a non-linear function, while the spectral envelope is extended in the cepstral domain using a multi-layer perceptron. Low-band extension is based on the sinusoidal model. The amplitude of sinusoids is also estimated using a multi-layer perceptron. The results show that the sound quality after extension is higher than that of narrowband speech, with a significant variation across listeners. Some of the techniques, including excitation extension, are of interest in the field of speech coding. ----- Le pr\'esent m\'emoire propose un syst\`eme d'extension de la bande permettant de produire un signal en bande AM \`a partir d'un signal de parole en bande t\'el\'ephonique. L'extension est effectu\'ee de fa\c{c}on ind\'ependante pour les hautes fr\'equences et les basses fr\'equences. L'extension des hautes fr\'equences utilise le mod\`ele filtre-excitation. L'extension de l'excitation est r\'ealis\'ee dans le domaine temporel par une fonction non lin\'eaire, alors que l'extension de l'enveloppe spectrale s'effectue dans le domaine cepstral par un perceptron multi-couches. L'extension de la bande basse utilise le mod\`ele sinuso\"idal. L'amplitude des sinuso\"ides est aussi estim\'ee par un perceptron multi-couches. Les r\'esultats obtenus montrent que la qualit\'e sonore apr\`es extension est sup\'erieure \`a celle de la bande t\'el\'ephonique, avec une importante diff\'erence entre les auditeurs. Certaines techniques d\'evelopp\'ees, dont l'extension de l'excitation, pr\'esentent un certain int\'er\^et pour le domaine du codage de la parole.