Construction and first evaluation of the Italian Matrix Sentence Test for the assessment of speech intelligibility in noise

Speech intelligibility is a crucial factor in everyday communication which can be estimated under controlled conditions using speech intelligibility tests. Besides the application on diagnostic purposes, speech intelligibility tests can be used for evaluating speech intelligibility in realistic rooms like offices, classrooms or auditoriums. Therefore, well standardised speech intelligibility tests and methods which are comparable across languages are needed. The current work presents the evaluation procedure and results of normally hearing listeners of the newly developed Italian Matrix Sentence Test for assessing speech reception thresholds (SRT, i.e. signal-to-noise ratio of 50% intelligibility) in noise. The test is composed of a matrix of ten names, verbs, numerals, nouns and adjectives which get randomly combined to create syntactically fixed but semantically unpredictable sentences. The goal of the evaluation measurements was to investigate the equivalence of test lists, examine the training effect and establish the reference data for normally hearing listeners. Speech intelligibility measured at three fixed SNRs showed comparable list-specific intelligibility functions, which resulted in a mean SRT and slope of -7.3 ± 0.2 dB and 13.3 ± 1.2 %/dB, respectively. To investigate the training effect and establish reference data, speech intelligibility was measured adaptively with 6 test lists of 20 sentences using an open- and a closed-set test format. The major training effect of about 1.5 dB was observed for the first two consecutive measurements which was also found for matrix sentence tests in other languages. From the third till the 6th measurement improvements in SRT were rather small with average thresholds of 6.7 ± 0.7 dB and 7.4 ± 0.7 dB for the open- and closed-set test format, respectively. The optimised and evaluated Italian Matrix Sentence Test will be used for speech intelligibility measurements with pupils in classrooms.