Semester

Spring

Date of Graduation

2005

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Industrial and Managements Systems Engineering

Committee Chair

Steven Guffey.

Abstract

Noise enclosures are an important tool in reducing noise exposures. Holes in enclosures are known to reduce the effectiveness of such enclosures. There are methods to predict the effects of openings, but those methods are largely untested in real enclosures. This study investigated the effects of hole size (0%, 0.024%, 0.379%, 0.675%, 1.492%,and 5.063%) at a distance of 5 feet (1.524 m) in a 96 inch (2.46 m) x 37 inch (0.94 m) x 31 inch (0.79 m), 3/4 inch plywood enclosure with a noise source centered in the box and the openings centered on one long face of the box. The enclosure was tested inside a relatively live room (Approx. R = 3000 ft2).;Results showed that no predictive model accurately predicted behavior. As expected, noise reduction (NR) values varied inversely with opening areas. However, the relationship was not monotonic, possibly due to resonance frequencies inside the box. In fact, spikes in NR and values occurred at the wavelengths corresponding to 500 Hz. At 4000 Hz, it was observed that even a small opening area of 4 sq.inch reduced the insertion loss by 14 dB. On the other hand, at 500 Hz small openings did not significantly affect the Insertion Loss.

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