Introduction

This chapter describes test and evaluation procedures of performance associated with the various voice-quality applications. The telecommunications equipment marketplace is filled with a variety of echo canceler (EC) and voice-quality systems (VQS) promoted by different vendors. Noticeably, the characteristics and performance of these products are not identical. In addition, the non-uniformity and arbitrary judgment that is often introduced into the EC and VQS product-selection process makes the network operator's final decision both risky and error prone. This chapter describes the criteria and standards that are available to facilitate methods for objectively analyzing the benefits of EC and VQA technology when confronted with multiple EC and VQS selection choices. The scope includes procedures for evaluating the performance of electrical (hybrid), acoustic-echo control, noise reduction, and level optimization via objective, subjective, laboratory, and field-testing methods.

This chapter brings to light a list of tools and standards designed to facilitate the voice-quality assessment process. It is intended to provide a methodology for objectively analyzing the benefits of voice-quality assurance technology in situations where network operators are confronted with multiple VQA system choices.

Voice-quality application features required by network operators typically include the following capabilities:

• network hybrid (electrical)-echo cancelation,

• acoustic-echo control,

• automatic volume control,

• adaptive level control (noise compensation) as a function of surrounding noise,

• noise reduction,

• non-voice applications.

Voice-quality application and performance assessment criteria encompass the following areas:

• application features and performance,

• maintenance features,

• environmental considerations,

• reliability thresholds,

• density and heat-dissipation characteristics,

• level of integration with key infrastructure elements.

Judging audio quality and performance of hybrid-echo cancelation

The literature and descriptive material distributed by many VQS vendors tends to concentrate on specific strengths, while glossing over the technical details that are vital in deriving a complete and accurate assessment of the VQS capabilities.