Title page for ETD etd-08242006-180234


Type of Document Master's Thesis
Author Schwartz, Kyle Wayne
Author's Email Address kschwart@vt.edu
URN etd-08242006-180234
Title Acoustic Characterization and Preliminary Noise Control of Pneumatic Percussion Tools
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Burdisso, Ricardo A. Committee Chair
Inman, Daniel J. Committee Member
Johnson, Martin E. Committee Member
Keywords
  • Noise Control
  • Pneumatic Percussion Tools
  • Acoustic Characterization
  • Chipping Hammer
  • Phased Array
Date of Defense 2006-08-04
Availability unrestricted
Abstract
Pneumatic percussion tools are extensively used in the construction industry. They are one of the noisiest machines in the construction industry generating noise levels above 110 dBA which are well beyond the permissible exposure limit (PEL) of 85 dBA. This work presents a comprehensive methodology for the acoustic characterization and noise source identification of these percussion tools. The methodology is applied to a representative pneumatic tool and the characterization results are described in detail. A mechanical analysis was performed on a chipping hammer finding mode shapes and natural frequencies of individual components. The mechanical analysis included modal hammer measurements and creating FE models. Fluid measurements were performed on the chipping hammer to find the velocity of the exhaust and pressure in the upper and lower chambers. The fluid tests found that the velocity of the exhaust is approximately Mach 1.0 or greater. Noise measurements were carried out on the chipping hammer to determine the spectral characteristics, overall sound power level, and spatial source strength maps of the tool. A spherical array of microphones was used to obtain an accurate estimate of the overall sound power levels and the directivity. The overall sound power radiation was found to be in the range of 110-115dBA. An advanced 63 microphone phased array was used to successfully locate and identify the major sources of noise from this tool via the use of beam-forming maps. This thesis also presents a preliminary noise control method employing commercial-off-the-shelf pneumatic silencers. The outcome of the tests is illustrated in detail in this thesis.
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