Measuring Noise Level Reduction Using an Artificial Noise Source and Test House

Measurements and analyses were performed to characterize methods of measuring Noise Level Reduction (NLR) for buildings using a loudspeaker. The study was tasked with quantifying the impacts of various factors such as the angular and elevation location of the loudspeaker. NLR measurements were taken using a "test house" that was constructed for the study. The results of the analysis may provide a better understanding of NLR measurement procedures. NLR is a common metric used to quantify the ability for a building element to reduce the transmission of exterior noise. While NLR may be measured using an actual traffic source (e.g., aircraft fly-overs), another option has been to perform measurements using a loudspeaker. Among NLR measurement procedures evaluated here, "moving microphone" methods were found to be most repeatable. Variations in NLR results with respect to angular and elevation position of the loudspeaker did not exhibit controllable, predictable behavior. These results imply that while single-point loudspeaker based methods may be suitable for assessing relative changes in NLR ('before" vs. "after"), they may not be robust for estimating absolute NLR. To obtain acceptable agreement between flyover-based vs. loudspeaker-based measurements will likely require additional loudspeaker measurement locations, and possibly variation in the source signal.