Effects of Cross-Sectional Dimensions on Active Noise Control in Rectangular and Round Ducts

Details

• Personal Author:
  Guffey S ; Slagley JM ; Guffey S ; Slagley JM
• Description:
  Active noise control (ANC) works best to reduce low frequency noise. Because many industrial noise sources are broadband, ANC may be used more if it can be successfully applied to higher frequency ranges. This study explored one method to increase ANC effectiveness at higher frequencies. ANC is particularly useful in hard-walled ducts where plane waves propagate. Higher order mode waves are much more difficult to control. Basic acoustic principles dictate that the cut-on frequency at which higher order modes will first begin to eclipse simple plane waves in a duct will be determined by the cross-sectional geometry of the duct. The lowest frequency for higher order modes increases as duct diameter decreases; therefore the range of frequencies where plane waves dominate will be greater and effective control using ANC will be better as duct diameter decreases. The result is that somewhat higher frequencies can be controlled with ANC for smaller diameters. Below the first higher order mode cut-on frequency for the largest size studied, there should be little difference in ANC effectiveness between the duct sizes. To test those suppositions, a commercially available ANC system was used to reduce random noise in rectangular and round ducts having different diameters. Results showed that insertion loss (IL) ranged from 5 dB to 29 dB in frequencies ranging from 40-1000 Hz and varied inversely with cross-sectional size as expected. There was no difference in IL below 280 Hz (p = 0.7751) between the different diameter ducts. There was a significant difference between duct diameters above 280 Hz (p < 0.0001). The same tests were conducted on a rectangular duct with one cross-sectional dimension fixed and one varied at seven different sizes. Results showed similar IL from 5 dB to 29 dB that varied inversely with size. [Description provided by NIOSH]
• Subjects:
  Engineering Noise Noise, Occupational Occupational Health Safety
• Keywords:
  Acoustics Author Keywords: Active Noise Control Duct Diameter Engineering Controls Engineering Noisecontrol Industrial Noise Noise Cancellation Noise Control Noise Frequencies
• ISSN:
  1545-9624
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article ; Journal Article
• Place as Subject:
  Ohio ; OSHA Region 3 ; OSHA Region 5 ; West Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH) ; National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health ; Workplace Safety & Health
• Location:
  North America ; North America
• Pages in Document:
  492-501
• Volume:
  4
• Issue:
  7
• NIOSHTIC Number:
  nn:20069898
• Citation:
  J Occup Environ Hyg 2007 Jul; 4(7):492-501
• Contact Point Address:
  Jeremy M. Slagley, Air Force Institute of Technology, Systems and Engineering Management, AFIT/ENV Bldg. 640, 2950 Hobson Way, Wright-Patterson AFB, OH 45433-7765
• Email:
  jeremy.slagley@afit.edu
• Federal Fiscal Year:
  2007
• Performing Organization:
  West Virginia University
• Peer Reviewed:
  True
• Start Date:
  20050701
• Source Full Name:
  Journal of Occupational and Environmental Hygiene
• End Date:
  20100630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:c9f922974f0514de1341388660505f309ea32faa5747b22af44d9eb3ea561856dadb8ce035fe941a02d2a26993906e6dba7a844a4c3c413a512bfac300a024c8
• Download URL:
  https://stacks.cdc.gov/view/cdc/208233/cdc_208233_DS1.pdf
• File Type:
  [PDF - 602.13 KB ]