On the combined effects of early- and late-arriving sound on spatial impression in concert halls.

This paper describes six new experiments involving subjective ratings of the listener envelopment, LEV, and the apparent source width, ASW, of simulated sound fields. Previous work has identified LEV and ASW as the principal components of spatial impression in concert halls and has shown that ASW is primarily influenced by the level of early lateral reflections and LEV by late-arriving lateral reflections. The new results in this paper show that LEV can result from nonlateral late-arriving sounds and demonstrate the conflicting effects of early- and late-arriving lateral sound on ASW and LEV when both are present, as would occur in real halls. While it is possible to create simulated sound fields with only either LEV or ASW, in typical concert halls, the balance between early- and late-arriving lateral sound will determine the relative importance of LEV and ASW. LEV and ASW are shown to be perceived when the critical components of the sound field are salient relative to other components. The results of the new subjective studies were used to estimate expected ASW and LEV in 16 halls. In these halls LEV is predicted to be the stronger component of spatial impression.

On the combined effects of signal-to-noise ratio and room acoustics on speech intelligibility.

Speech intelligibility in rooms is influenced by room acoustics effects and by the signal-to-noise ratio (S/N) of the speech and ambient noise. Several measures such as useful-to-detrimental sound ratios and the speech transmission index predict the combined effects of both types of factors. These measures were evaluated relative to speech intelligibility test results obtained in simulated sound fields. The use of simulated sound fields made it possible to create the full range of combinations of room acoustics and S/N effects likely to be found in rooms for speech. The S/N aspect is shown to be much more important than room acoustics effects and new broadband useful-to-detrimental ratios were validated. Useful-to-detrimental ratios, speech transmission index measures, and values of the articulation loss for consonants were all reasonably accurate predictors of speech intelligibility. Further improvements to these combined measures are suggested.