Final Discussion and Conclusions

Abstract

The quality of telephone speech is a multidimensional property. It arises when certain perceivable characteristics of the speech itself meet the users expectations and desires. Speech as such does not carry a quality in itself. Quality is an event, and consequently it can only be established in a specific situation. A schematic describing the constitutional components of the quality of a telecommunication service has been developed. This schematic is meant to be user directed, in the sense that different dimensions of quality are related to concepts of usability, utility or acceptability. The latter describe at which different levels the performance of a telecommunication service is affected in the eyes (ears) of the user. The entities of the schematic have been put into relation with characteristics of the transmission system that have an impact on certain quality features. To gain a better understanding of the perceptive factors which result in percepts of loudness, articulation or disturbance during the conversation, the psychoacoustic background has been presented. This background is also the basis of one of the transmission rating models discussed later on.