Speech and noise levels in classrooms—signal, noise, reverberation levels as a metric for acoustic design for learning

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This study attempts to investigate the variance of speech levels in occupied classrooms during learning activities and their relationship to the total noise component (occupied, ambient, and reverberant). The methodology for the construction of a valid data base is presented, which would apply to criteria such as SNR (signal-to-noise ratio) and correlate to the term SNRL (signal, noise, reverberation levels). The interrelationship of speech and noise in any learning environment requires that the common variables associated with a stated speech level value should be stated along with the speech level value. The significance of the influences on the global value and in some cases the spectra of speech is discussed relative to variables such as the activity, the total occupancy and comportment of the audience, the volume of the room, total occupied noise in proximity to the speaker, speech directivity, effects of head diffraction among seated audience, and the distance from the source. Results from measurements taken in this study in actual classrooms are presented with an emphasis on specificity. This research has produced a strategy for the mapping of the speech-noise environment that significantly supports the use of a modeled SNR value as a goal for design.