Ville Myllylä

Pseudo-optimal regularization for affine projection algorithms

In the application of acoustic echo cancellation the adaptation process is disturbed by local background noise as well as by the speech of the local speaker. Furthermore, the loudspeaker-enclosure-microphone (LEM) system has time-variant nature. Therefore, adaptation control is absolutely necessary. If fast algorithms like affine projection are applied also numerical stability problems caused by matrix inversion arise. In this contribution both problems are addressed and by introducing a pseudo-optimal regularization a common solution is derived.

Development, evaluation and implementation of an artificial bandwidth extension method of telephone speech in mobile terminal

Artificial bandwidth extension methods aim to improve the quality and intelligibility of narrowband telephone speech by adding new, artificially generated spectral content to the highband of the received voice signal. The development cycle of an artificial bandwidth extension method from the initial idea to the implementation in a mobile terminal is discussed in this paper. Developing the algorithm in the Matlab environment was the first step in the process. The method was then evaluated in formal listening tests and simulations to verify its performance in different scenarios. Finally, the utilization of this technology in a product included its DSP implementation combined with the acoustical design of the user terminal.

Acoustic Echo Cancellation for Dynamically Steered Microphone Array Systems

A new method for integrating dynamically steered beamforming filters and acoustic echo cancellation is presented. The proposed method enables beam steering independent AEC processing without parallel AEC filters for each microphone input (a.k.a. AEC-first configuration). Especially for larger microphone arrays the proposed method can provide significant computational savings with comparable performance to AEC-first configuration.

Adaptive beamforming methods for dynamically steered microphone array systems

This paper introduces two methods for the integration of a dynamically steered beamforming filter with acoustic echo cancellation (AEC) and adaptive generalized sidelobe canceler (GSC) based beamforming methods. We evaluate the performance of a beamforming system with moving and changing source positions. Individual contributions of adaptive beamforming and steering independent AEC processing methods are evaluated for high level echo cancellation in a typical office environment. The results show that the proposed adaptive beamforming method increases the overall AEC performance even if GSC adaptation would be disturbed by dynamic beam steering.

A subjective listening test of six different artificial bandwidth extension approaches in English, Chinese, German, and Korean

In studies on artificial bandwidth extension (ABE), there is a lack of international coordination in subjective tests between multiple methods and languages. Here we present the design of absolute category rating listening tests evaluating 12 ABE variants of six approaches in multiple languages, namely in American English, Chinese, German, and Korean. Since the number of ABE variants caused a higher-than-recommended length of the listening test, ABE variants were distributed into two separate listening tests per language. The paper focuses on the listening test design, which aimed at merging the subjective scores of both tests and thus allows for a joint analysis of all ABE variants under test at once. A language-dependent analysis, evaluating ABE variants in the context of the underlying coded narrowband speech condition showed statistical significant improvement in English, German, and Korean for some ABE solutions.

Conversational quality evaluation of artificial bandwidth extension of telephone speech

Artificial bandwidth extension methods have been developed to improve the quality and intelligibility of narrowband telephone speech and to reduce the difference with wideband speech. Such methods have commonly been evaluated with objective measures or subjective listening-only tests, but conversational evaluations have been rare. This article presents a conversational evaluation of two methods for the artificial bandwidth extension of telephone speech. Bandwidth-extended narrowband speech is compared with narrowband and wideband speech in a test setting including a simulated telephone connection, realistic conversation tasks, and various background noise conditions. The responses of the subjects indicate that speech processed with one of the methods is preferred to narrowband speech in noise, but wideband speech is superior to both narrowband and bandwidth-extended speech. Bandwidth extension was found to be beneficial for telephone conversation in noisy listening conditions.

Conversational Evaluation of Speech Bandwidth Extension Using a Mobile Handset

The quality of narrowband telephone speech can be improved by artificial bandwidth extension. So far, bandwidth extension methods have been evaluated with objective measures and subjective listening-only tests, whereas realistic conversational evaluations have been rare. This article presents a conversational evaluation of two bandwidth extension methods in comparison with narrowband and wideband references. The evaluation was carried out using a mobile handset with a wired earpiece and microphone both in silence and in simulated street noise. The results indicate that speech processed with one of the bandwidth extension methods was preferred over narrowband speech.

Conversational evaluation of artificial bandwidth extension of telephone speech using a mobile handset

Artificial bandwidth extension methods have been developed to improve the quality and intelligibility of narrowband telephone speech. Bandwidth extension methods have typically been evaluated with objective measures or subjective listening-only tests, whereas realistic conversational evaluations have been rare. This paper presents a conversational evaluation of two bandwidth extension methods together with narrowband and wideband speech. The evaluation was performed using a mobile handset with a wired earpiece and microphone both in silence and in simulated street noise. The results indicate that one of the evaluated bandwidth extension methods was significantly preferred over narrowband speech in silence. The results also suggest slight preference for this bandwidth extension method over narrowband speech in street noise. True wideband speech was considered superior to bandwidth-extended and narrowband speech especially in silence.