Acoustical Standards for Classroom Design Comparison of International Standards and Low Frequency Criteria

摘要

Many countries have acoustical standards or regulations for educational facility design and construction. They are based on speaking and hearing abilities of teachers and learners. Criteria are often stipulated for reverberation decay time, sound isolation and allowable background noise. The standards may use single number A-weighted overall level descriptors (dBA), or octave band spectrum criteria (NC, RC, NR, etc.). A-weighted overall level criteria control mid- to high frequencies better than lower frequencies. Very few, if any countries specify low frequency noise standards, although limitations are implicit in spectrum criteria curves, such as (North American) Noise Criteria (NC) or Room Criteria (RC) or (European) Noise Rating (NR). Many educators focus on mid- to high-frequency effects on speech intelligibility, but low frequency noise (LFN) may cause some (upward) masking of speech with reduction of intelligibility. In addition, LFN may affect student attitudes, behavior, performance and/or fatigue. This paper compares.acoustical criteria from several countries with respect to spectrum. Frequency spans of reverberation, sound isolation and background noise are contrasted with hearing and speech characteristics of children and adult learners. Principal findings of some LFN research by others are introduced, such as annoyance, speech intelligibility and fatigue. While this paper does not present a quantitative measure or model for low frequency noise versus learning, it investigates links between acoustical environment and learner success potential. Tabular comparisons of acoustical criteria and graphic charts of representative criteria will be presented. General recommendations are made, based on findings inferred from review and comparispn of standards.