Date of Award

2019

Document Type

Open Access Master's Report

Degree Name

Master of Science in Mechanical Engineering (MS)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Andrew R. Barnard

Committee Member 1

Jason R. Blough

Committee Member 2

Darrell L. Robinette

Abstract

In today’s world, noise pollution is growing as a major concern and it is becoming more and more difficult to find quiet places. But when the problem escalates to the extent that people are annoyed with loud noises even in their apartments, it becomes an alarming issue for engineers. Around the world, cities have defined some basic performance requirements for buildings, and isolation of residents from noise is one of the cardinal performance requirements. In the United States, building codes use the Impact Insulation Class (IIC) rating to characterize the performance of floor/ceiling assemblies. This method uses the response measured in one-third octave (OTO) bands from 100 Hz to 3150 Hz and compares it with a reference curve to obtain the rating. However, this standard suffers from some limitations. The standard assumes the receiving rooms in the testing labs to be modally dense for all frequency OTO bands under consideration but the labs usually have a non-modally dense acoustic environment for low-frequency bands. Due to this, different labs give different results for the same assembly, thereby making it difficult to get reproducible IIC measurements. With the method proposed in this report, the room contribution for these low-frequency OTO bands could be removed, paving a way to obtain more reproducible IIC measurements. This room contribution is removed by using a reference calibration assembly with a known sound power and employing the comparison technique. The comparison of measurements of the reference assembly in the test labs with the known sound power gives a calibration factor, defining how the room contribution affects the measurement data. These calibration factors are then used for the actual assemblies to get to the “true” sound power, unbiased by the effects of room contribution. This report uses a simply supported rectangular plate as a reference assembly and analytically calculates the mode shapes, mobility, and sound power radiation. These analytical predictions are compared with the experimentally obtained values. This reference assembly is then used in a reverberation room to characterize the room contribution in one-third octave bands. The reference assembly is then replaced by a new, unknown assembly, and the “true” sound power information is predicted using the proposed method.

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