Measurement of the ambient in relocateable modular classrooms.

Abstract

The ambient in a classroom consists of noises internal to the classroom (e.g., HVAC, lighting, IT equipment, refrigerators, and fish tank pumps) and noises external to the classroom (e.g., street traffic, aircraft, children in the playground, and adjacent classroom noise). Currently, ANSI S12.60, Classroom Acoustics, requires that the A‐weighted ambient level, unoccupied, be less than 35 dB at the noisiest position in the classroom. A basic reasonable procedure to implement the required measurements has been developed and tested. The authors find that the procedures developed can be readily used by inexperience but technically oriented individuals. The procedure separates the measurement of internal and external noises into two measurements, typically at different positions. Because the two noises are variable, unrelated in position, and uncorrelated in time, it does not make sense to combine them in any fashion. Rather, in the procedure to be recommended by WG 68, the two measurements are to be reported and evaluated, separately, against the 35 dB criterion. Other notable changes are expansion of the measurement hours to include busy traffic periods (high environmental noise periods) prior to and after school and on Saturdays, and implementation of HVAC duty cycles to better estimate a typical A‐weighted hourly equivalent level from HVAC equipment (the subject of a companion paper).