Low Bit-rate Coded Speech Intelligibility Testing in Czech Language using Parallel Task

Abstract

This article deals with subjective tests of speech intelligibility. A set of samples in Czechlanguage, recorded by four different narrators, was distorted with different noise levels andencoded by a low bit-rate encoder. The subjective test consisted of two parts. The first part(45 participants) proceeded according to the ITU-T Recommendation P.807 - Subjective testmethodology for assessing speech intelligibility. The second part (70 participants) included anadditional (parallel) psychomotor task deploying a laser-shooting simulator, where subjectshad the roles of “shooters” and “counters”. The purpose of the parallel task is to bring thetesting closer to the real use of technology. Significant differences have been found in theresults of the intelligibility of samples from different speakers. There were also differences inevaluation with and without a parallel task. Samples from male narrators have a significantlyhigher intelligibility score in the standard laboratory test, but also show a greater decrease inintelligibility after engaging a parallel task.