Validation of a sound intensity imaging system for wall ISTC calculation, with leak detection

Roderick KT Mackenzie, Boudreault Louis-Alexis, Pearson Michel


This paper presents a comparison study of two methods that can be used for calculating the sound transmission classification (STC) of a sample wall in a test laboratory, as per ASTM E2249-2016. In both methods, the average sound pressure level within a reverberant room is taken, and the incident sound power on the wall in the source room is calculated.  In the 1st method, the traditional method of E2249, an intensity probe is swept at a constant speed, across a set path, through a wire-frame grid specially constructed for the measurement. The sound power radiating from the whole wall is then calculated from the sound intensity, and the sound transmission loss is calculated by subtracting the radiated sound power of the wall from the incident sound power. Having calculated the TL, the STC can then be calculated via ASTM E413-2016. In the 2nd method, the sound intensity probe of the I-track sound intensity imaging system is swept across the wall surface at both an irregular speed and an irregular pattern. The sound power is instantly calculated by the software, as optical tracking of the probe means the spatial and temporal sampling of the sound intensity is made automatically. The sound power is then used to calculate the STC in the same manner as the traditional method.
The paper presents the precision of the two methods (traditional vs imagery). Additionally, the paper will present a secondary benefit from the use of the imagery method not available to the traditional scan method; the ability to locate and rank acoustical weaknesses within the single surface scan.



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