Dealing with measurement uncertainties in building acoustics

Reine Johansson,Sean Smith,María Machimbarrena,Stefano Pedersoli,Carolina Rodrigues A Monteiro,Bernard Larquier

doi:10.1051/metrology/20150004005

Abstract

Building acoustics is a field where uncertainties have traditionally been reported as stated by an existing standard, or not reported at all. In a world where acoustic performance of building elements (measured in accredited laboratories) and acoustic performance of constructive solutions (measured in the field) must be tested and often judged to comply with a requirement, it is recommended to perform detailed uncertainty calculations. The existing standard “ISO 12999–1:2014 Determination and application of measurement uncertainties in building acoustics - Part 1: Sound insulation ” includes general uncertainty values for typical measurands such as airborne and impact sound insulation under different measurement situations, both for third octave bands and single number quantities. This paper supports the idea of making individual uncertainty calculations not only for sound insulation measurements but for any acoustic measurement in building acoustics. A collection of such calculations are shown to support the thesis, showing that this individual uncertainty calculation becomes more important when single number quantities are considered.

Highlights

The measurement of sound insulation in buildings and of building products is a continuously changing field
Some parts consider that the uncertainty of a sound insulation measurement shall be stated as the uncertainty of the corresponding measurement method, based on the results of interlaboratory measurements described in ISO 12999-1 and no individual uncertainty calculation is performed
This frequency dependent result can be converted into a single number quantity (SNQ) following different procedures [19, 20], and it is the SNQ which must be reported in order to verify compliance with a Building Code requirement

Summary

Introduction

The measurement of sound insulation in buildings and of building products is a continuously changing field. According to some authors [7, 8], it is not possible to follow a GUM [9] approach to determine uncertainties of sound insulation measurements, or it seems reasonable to keep the idea of reproducibility and repeatability. The measurand can for example be the sound pressure level, sound power level, sound reduction index or a single number quantity like DnT,A In reality this usually means to sample one value out of a universe of possible values, since in general, when one repeats a measurement, one will obtain different answers. If experience indicates that the estimated correlation coefficient is not bigger than for example 0.8, this is the number to use in the measurement uncertainty calculations The former problem for GUM, with strongly nonlinear systems, has been solved by introducing a GUM Supplement [9]. This is why making individual uncertainty calculations in the field of building acoustics is encouraged in this paper

Objective

Results from a case study

Conclusions