No abstract

/npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://dx.doi.org/10.1121/1.1570439 America, 113, 6, pp. 3233-3244, 2003-06-01 On the importance of early reflections for speech in rooms Bradley, J. S.; Sato, H.; Picard, M. Journal of the Acoustical Society of On the importance of early reflections for speech in roomsBradley, J.S.; Sato, H.; Picard, M. Lochner and Burger's results suggest that speech energy in early arriving reflections is more or less equivalent to similar amounts of direct speech energy in terms of increasing speech intelligibility scores. They developed the concept of useful-to-detrimental sound ratios in which 'useful' is defined as the sum of the direct and early-reflected speech energy and 'detrimental' is the sum of the later-arriving speech reflections and the ambient noise. This concept has been shown to be well correlated with speech intelligibility test scores in a wide range of rooms [5][6][7] and to be strongly correlated [8] with the newer speech transmission index (STI) concept. NRCC-45431 A version of this document is published in / Une Early reflections for speech -3However, Bess [9] has recently claimed that the benefits of early reflections are not experienced by impaired listeners. This is in contradiction with the results of Náb lek and Robinette [10] that indicated normal hearing and impaired listeners benefited equally from a single added early reflection. In addition, the importance of early reflections in rooms is apparently not well appreciated in conventional room acoustics design which is usually based primarily on obtaining a particular preferred reverberation time [11]. A lack of appreciation of the importance of early reflections is no doubt responsible for some recommendations for very short reverberation times for rooms for speech. There is often a misconception that reverberation time must be minimized rather than optimised.Of course, very short reverberation times require increased absorption on room surfaces which is likely to lead to reduced early reflection energy and hence to reduced speech intelligibility.There are many situations in speech communication in rooms where early reflections would appear to be particularly important such as a teacher talking to students from somewhere in the middle of a classroom or an actor on a thrust stage. Students behind the teacher would receive muc...

No abstract

This is the second of two papers describing the results of acoustical measurements and speech intelligibility tests in elementary school classrooms. The intelligibility tests were performed in 41 classrooms in 12 different schools evenly divided among grades 1, 3, and 6 students (nominally 6, 8, and 11 year olds). Speech intelligibility tests were carried out on classes of students seated at their own desks in their regular classrooms. Mean intelligibility scores were significantly related to signal-to-noise ratios and to the grade of the students. While the results are different than those from some previous laboratory studies that included less realistic conditions, they agree with previous in-classroom experiments. The results indicate that +15 dB signal-to-noise ratio is not adequate for the youngest children. By combining the speech intelligibility test results with measurements of speech and noise levels during actual teaching situations, estimates of the fraction of students experiencing near-ideal acoustical conditions were made. The results are used as a basis for estimating ideal acoustical criteria for elementary school classrooms.

No abstract