Abstract
In general, uncertainties should preferably be determined following the principles laid down in ISO/IEC Guide 98-3, the Guide to the expression of uncertainty in measurement (GUM:1995). According to current knowledge, it seems impossible to formulate these models for the different quantities in building acoustics. Therefore, the concepts of repeatability and reproducibility are necessary to determine the uncertainty of building acoustics measurements. This study shows the uncertainty of field measurements of a lightweight wall, a heavyweight floor, a façade with a single glazing window and a façade with double glazing window that were analyzed by a Round Robin Test (RRT), conducted in a full-scale experimental building at ITC-CNR (Construction Technologies Institute of the National Research Council of Italy). The single number quantities and their uncertainties were evaluated in both narrow and enlarged range and it was shown that including or excluding the low frequencies leads to very significant differences, except in the case of the sound insulation of façades with single glazing window. The results obtained in these RRTs were compared with other results from literature, which confirm the increase of the uncertainty of single number quantities due to the low frequencies extension. Having stated the measurement uncertainty for a single measurement, in building acoustics, it is also very important to deal with sampling for the purposes of classification of buildings or building units. Therefore, this study also shows an application of the sampling included in the Italian Standard on the acoustic classification of building units on a serial type building consisting of 47 building units. It was found that the greatest variability is observed in the façade and it depends on both the great variability of window’s typologies and on workmanship. Finally, it is suggested how to manage the uncertainty in building acoustics, both for one single measurement and a campaign of measurements to determine the acoustic classification of buildings or building units.
Highlights
This paper is a revised and expanded version of the paper “Uncertainty in Building Acoustics” [1]presented at the 22nd International Congress on Sound and Vibration ICSV22.When reporting the result of the measurement of a physical quantity, it is compulsory that some quantitative indications of the quality of the result be given so that those who use it can assess its reliability
When measurements are made to verify the acoustic requirements of buildings, one single measurement might not be enough to this end, and more measurements and more results for the same requirement are necessary
A sample survey is the best solution in terms of cost and time
Summary
This paper is a revised and expanded version of the paper “Uncertainty in Building Acoustics” [1]. Two measures of precision, termed repeatability and reproducibility, have proved necessary and, for many practical cases, sufficient for describing the variability of a test method. The quantities that have to be measured and their measurement methods, for all aspect involved, are described in the international standard series EN ISO 10140 [3] for laboratory measurements and in the international standard series ISO 16283 [4] for field measurements The accuracy of these measurement method depends on several factors that influence the test, such as acoustic instrumentation, acoustic method (microphones and sources position), context (regular rooms or semi-open space, of any size), constructive details of the building (that could have effect on acoustic measures) and workmanship, and, concerning sound levels, influence of instrumentation working conditions (repeat configuration). The in situ standard deviation, corresponds to a reproducibility standard deviation of the same object in the same location
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