In the last few years there has been a dramatic development in voice communications technology with a significant move towards Voice over the Internet Protocol (VoIP). However, since IP was primarily designed for best-effort networking technology, good quality conversation and intelligibility are not always guaranteed. In this chapter, the authors address the most relevant methods used to evaluate the voice quality in the communications context of modern enterprises, where VoIP is used as an emerging technology with impact in their activity. Relevant factors for service providers and enterprises using VoIP technology are described, such as those related to the measurement of intelligibility and with impact on the overall voice communications quality. In addition, the most important voice quality evaluation methods recommended by the International Telecommunication Union (ITU) are presented in this chapter, along with the main features that can be used to improve voice communications. Fundamental concepts behind voice quality evaluation models are highlighted, such as intrusive, non-intrusive, objective, subjective, and parametric methods. After addressing the most relevant theoretical and methodological aspects, a recent application of voice quality monitoring for VoIP communications is described as the result of a research and development project. After its successful implementation, this monitoring system is now fully operational and integrated in voice quality assessment equipment currently in the market.
