British Telecommunications Public Limited Company

British Telecommunications Corporation

Psytechnics Limited

Philip Gray

Michael Peter Hollier

Antony William Rix

Richard J B Reynolds

Richard Jb Reynolds

Philip J Sheppard

Ludovic Malfait

Non-intrusive speech-quality assessment uses vocal-tract models, in particular for testing telecommunications systems and equipment. This process requires reduction of the speech stream under assessment into a set of parameters that are sensitive to the types of distortion to be assessed. Once parameterized, the data is used to generate a set of physiologically-based rules for error identification, using a parametric modeling of the shape of the vocal tract itself, by comparison between derived parameters and the output of models of physiologically realistic forms for the vocal tract, and the application of physical constraints on how these can change over time.

Speech-quality assessment method and apparatus that identifies part of a signal not generated by human tract

The degree of degradation imposed on signals transmitted over a communications link from a transmitter to a receiver is tested. A predetermined test signal is transmitted using spare capacity detected by a voice activity detector when no speech is to be transmitted over the communications link. The test signal received by the receiver is compared with the reference signal, and a measure of the degradation of signals caused by the communications link is generated therefrom.

Test signalling

A non-intrusive speech quality assessment system. A method and apparatus for training a quality assessment tool in which a database comprising a plurality of samples, each with an associated mean opinion score, is divided into a plurality of distortion sets of samples according to a distortion criterion; and a distortion specific assessment handler for each distortion set is trained, such that a fit between a distortion specific quality measure generated from a distortion specific plurality of parameters for a sample and the mean opinion score associated with said sample is optimised. A method and apparatus for assessing speech quality in a telecommunications network in which a dominant distortion type is determined for a sample; a distortion specific plurality of parameters are combined to provide a distortion specific quality measure for each sample; and a quality measure is generated in dependence upon the distortion specific quality measure.

Quality assessment tool

The perceptual quality of voice signals used for Voice over IP (VoIP) systems is assessed. The content of the voice data packets may be altered in order to increase the perceived quality of the VoIP system.

Method to reduce the distortion in a voice transmission over data networks

The present invention provides a test method which can determine whether a user terminal is capable of supporting a real time connection, such as a computer telephony link, with a network terminal while simultaneously supporting a connection with a WWW server.

Method to assess the quality of a voice communication over packet networks

The perceptibility of degradations caused to signals transmitted over a transmission medium is measured by generating one or more predetermined transmission degradation conditions (e) and subjecting a test signal (S) to the transmission degradation conditions (e) in a network simulation device. The degree M(e) to which the or each transmission degradation condition (e) is perceptible to the human perceptual system is measured and a data set is generated and stored for converting one or more transmission degradation conditions (e) to respective values of perceptibility M(e). The data set may be a look-up table or an empirically determined formula. The data set may then be used on live traffic (S'), by identifying objectively measured transmission degradation conditions (e) in the received signal (S&#x2032;) and retrieving from the data set in the data storage means (7) a value of perceptibility (M) associated with the transmission degradation conditions (e) so identified. In this way a measure of the subjective significance of degradation in the signal (S&#x2032;) can be derived from objective measures of degradation.

Training process for the classification of a perceptual signal

Trained artificial neural networks using an imperfect vocal tract model

A training apparatus for establishing the network definition function of a trainable processing apparatus, such as, for example, a neural network, is disclosed. The training apparatus analyzes a signal and includes means for providing a training sequence, the training sequence including a first signal and a distorted version of the first signal. The training sequence is transmitted to an analysis means which generates a distortion perception measure that indicates the extent to which the distortion would be perceptible to a human observer. The network definition function is determined by applying the distortion perception measure to the trainable processing apparatus.

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Ipswich, United Kingdom

Philip Gray