Instantaneous and overall judgements for time-varying speech quality: Assessments and relationships

This study investigates the perception of time-varying speech quality in te lephony. Two experiments were conducted, in which a method of continuous ju dgement was used in order to study instantaneous reactions of listeners fac ing quality fluctuations over time, and their consequences on overall perce ived quality. The aim of the first experiment was to validate the method us ed for various quality evolutions over time. In a second experiment, the re lationship between instantaneous and overall judgements was investigated. T he results of the first experiment validate the method and show that subjec ts react with different time constants to large sudden quality degradations (about 10 seconds) or improvements (about 30 seconds). The second experime nt demonstrated that the location of a quality degradation or improvement i nfluenced subjects' overall judgements, revealing a recency effect.