On the importance of early reflections for speech in rooms

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...

Effects of source-to-listener distance and masking on perception of cochlear implant processed speech in reverberant rooms

“…The results of Poissant et al ͑2006͒ suggest that signals comprised largely of early reflections may be less intelligible for implant users than signals comprised largely of direct arrivals. This hypothesis, if true, has important implications for implant users since recommendations for improving classroom acoustics often include increasing the level of early reflections ͑Siebein et al, 2000;Bradley et al, 2003͒. One simple way to evaluate this hypothesis is to compare intelligibility scores for speech received at small SLDs ͑hav-ing strong contributions from direct sound͒ with those for speech received at large SLDs ͑having strong contributions from reflected sound͒. Listeners with normal temporal integration abilities would be expected to recognize speech at the front and rear of the room with equal facility ͓assuming equal sound pressure levels ͑SPLs͔͒; listeners showing deficits in integration ability would be expected to show significant differences between the two locations.…”

The Measurement and Calibration of Sound Reproducing Systems

“…Germane to this discussion are the findings of Bradley et al [23] indicating that for speech intelligibility-a crucial consideration for movies-it is the early reflections that are the main contributors. They concluded that early reflection energy arriving within about the first 50 ms following the direct sound has the same effect on speech intelligibility scores as an equal increase in the direct sound energy.…”

Relationship between room characteristics and speech intelligibility in contemporary churches in Malaysia

“…These room models may not only have a short distance between the sound source and its surrounded walls but also sloped ceilings above the sound source.It can be generally concluded that the lower ceiling height above the sound source and shorter distance between the sound source and its surrounding walls may provide higher speech intelligibility in the most parts of the room because they will help to provide strong early sound energy reflections. However, if the room ceiling height is not adequate enough to distribute the early reflections to the rear room, speech intelligibility will be poor relative to the other parts of the room [20]. …”