Predicting Speech Intelligibility In University Classrooms Using Geometrical Acoustic Simulations

Abstract

In university classrooms a suitable acoustic condition is necessary to enhance the productivity of students and the vocal comfort of lecturers. With this purpose international standards recently introduced new requirements on the quality of verbal communication. The goal of this work is to propose a procedure for predicting speech intelligibility in large learning spaces through geometrical acoustic simulations. The performance of the present approach is investigated using analytical prediction models as well as the measurements results in six university classrooms surveyed.

Effect of loudspeaker position and model on cognitive load, quality, clarity, and sentence recognition performance

“…3 This finding could have important ramifications not only for classrooms, but any venue involving a talker and listeners, such as auditoriums, indoor concerts, and speaking engagements. Our findings of the importance of loudspeaker position may be most helpful in drawing classroom designs for geometrical acoustic simulations, 39 Any speaker system designed to improve clarity in the speech range, such as use of low mass transducers, or increase signal-to-noise ratio, such as with line arrays, will only enhance the benefits shown by our findings. 40…”

“…3 This finding could have important ramifications not only for classrooms, but any venue involving a talker and listeners, such as auditoriums, indoor concerts, and speaking engagements. Our findings of the importance of loudspeaker position may be most helpful in drawing classroom designs for geometrical acoustic simulations, 39 Any speaker system designed to improve clarity in the speech range, such as use of low mass transducers, or increase signal-to-noise ratio, such as with line arrays, will only enhance the benefits shown by our findings. 40 It should be noted that in the current study that measures of word clarity and sound quality were subjectively measured, and the classic measure of mental effort or cognitive load-that of asking listeners to judge the amount of mental effort taken to transcribe the sentences-all three measures would point to "listening effort."…”

A Trial Acoustic Improvement in a Lecture Hall with MPP Sound Absorbers and FDTD Acoustic Simulations

“…With this purpose, the acoustic condition of a large university lecture hall has been simulated with a ceiling-mounted system of double-layer MPPs. Such a kind of large rooms shows the highest values of reverberation time at 500 and 1000 Hz (see Figure 4 in [27]), the same frequency range occupied by the human voice [47]. As too high values of reverberation time deteriorate speech intelligibility, a material whose sound absorbing properties are mostly centered in such a frequency range may return useful outcomes in acoustic treatments of existing university halls.…”

“…The room chosen as a case study is a historical lecture hall in the University of Bologna (see Figure 14). A previous campaign of acoustic measurements [27,49] in the hall allowed to collect the main room criteria [50] and intelligibility indexes [47]. The setting of sound source and receiver locations chosen for the measurements campaign is also provided in Figure 14.…”

“…After the experimental phase, the performance of MPPs was evaluated focusing on the application to large-scale rooms. In particular, the effects of MPPs as an acoustic treatment in an existing lecture hall previously surveyed [27] were explored by means of full-spectrum finite-difference time-domain (FDTD) simulations [28].…”