Issues in acoustic field testing of quiet modular classrooms

Abstract

Modular classrooms are important to American education: About 300,000 modular classrooms are currently in use by public school systems here. Good acoustical conditions for learning are no less vital for students in modular classrooms than stick-built classrooms. In an effort to promote good acoustics in modular classrooms, ANSI S12 Working Group 46 is seeking to standardize acoustic field testing. Their efforts are in response to key acoustical issues of modular classrooms: Excessive noise from HVAC (heating ventilating and air conditioning) systems, and poor airborne sound insulation from exterior noise sources. In a recent and notable advance, an HVAC system provider reported good progress in modular HVAC noise reduction: A ducted wall mounted system was used instead of the usual free blowing system with exposed fans. HVAC noise in the unoccupied room was near the maximum 35 dB level required by ANSI S12.60. Interior noise levels were so low that efforts to confirm their values were confounded by noise contamination from exterior sources. The relatively high interior ambient noise levels were due to poor airborne sound insulation. Lessons learned from recent field testing will be discussed. Results of airborne sound insulation tests, now in planning stages, will be reported if available.