Scenarios for economic conversation tests in telephone speech quality assessment

Abstract

In telephony, there is a permanent need for auditory testing of the effect of different types of impairment on speech communication quality. Though quality perception is different in listening-only and conversation situations, for economic (time and money) reasons, in most cases only listening-only tests are carried out to assess telephone speech quality. For some parameters, however, conversation tests are mandatory, as the parameter under investigation affects only the conversation situation (e.g., echo, delay). In order to overcome the limitations of conversation tests, new scenarios have been developed which allow the testing of around three times as many circuit conditions within one test session compared to conventional conversation test scenarios. The scenarios cover everyday situations of information exchange, and meet most of the basic requirements of quality assessment scenarios (naturalness, balance, comparability, clarity). The scenarios are available in three languages and have been successfully used by different telecommunication test laboratories. Comparison with listening-only test results shows that differences exist between the two types of quality judgments, which underlines the necessity for conversation tests in order to get more valid quality judgments. Modifications of the scenarios for mobile and Internet telephony situations are presented.