Objective and subjective assessment of the speech intelligibility in rooms with an Active Acoustic Enhancement Systems

Abstract

Speech Transmission Index (STI), apart from the Reverberation Time (RT), remains an important parameter used for the speech intelligibility assessment indoors. As the Active Acoustic Enhancement Systems (AAES) are getting more and more commonly used, it was verified how such systems affect speech perception. In accordance with the 3382-1 and 3382-2 regulations, objective parameters were measured in two enclosures with the AAES. The RT values varied from 0.91 to 1.61 [s] for the hall in Mińsk Mazowiecki and from 0.75 to 1.52 [s] in Puławy. The STI values varied from 0.57 to 0.64 in Mińsk Mazowiecki and 0.64 to 0.69 in Puławy. Despite the significant differences in the RT values, STI coefficients remained almost unchanged. The listening test was designed to verify if the subjectively assessed intelligibility would confirm the objective measurements' results. 50-element nonsense words (logatome) lists were used for in-situ experiments and, in the second part, binaural laboratory arrangement. Both parts involved over 120 listeners. Three scenes were selected: without AAES and two different AAES setups. In summary, subjective measurements' results were compared with the obtained STI, RT and Clarity (C50, C80) values to prove their importance in indoors speech intelligibility evaluation.