Effects of Cross-Sectional Partitioning on Active Noise Control in Round Ducts

Details

• Personal Author:
  Guffey S ; Slagley JM ; Guffey S ; Slagley JM
• Description:
  Active noise control (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 diameter of the duct. The lowest frequency for higher order modes will increase 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. If smaller diameters have broader frequency ranges that can be controlled with ANC, perhaps one could extend the frequency range for a large cross section by partitioning it into smaller cross sections using axial vane splitters. This hypothesis was tested by two methods of cross-sectional partitioning. Partitioning was achieved in one design by inserting a smaller duct inside a large duct. In a second design, a cross-shaped splitter was inserted inside the large duct. Summed ANC insertion loss (IL) at low frequencies (≤250 Hz) was at least 16 dB and at least 14 dB at middle frequencies (≥315 Hz). ANC IL results were 1.7 to 2 dB better for the large duct partitioned by a smaller inner duct than the large duct alone (p = 0.0146 for low frequency and p = 0.0333 for middle frequency). ANC insertion loss was 5.6 dB better for the large duct partitioned by a cross-shaped splitter at high frequencies than the large duct alone (p = 0.0003). However, the cross-shaped partition system was 5.8 dB less effective at low frequencies than the large duct ANC IL alone (p < 0.0001). [Description provided by NIOSH]
• Subjects:
  Engineering Noise Noise, Occupational Occupational Health Safety
• Keywords:
  Acoustics Author Keywords: Active Noise Control Axial Vane Splitters Engineering Controls Industrial Noise Noise Cancellation Noise Control Partitioning Round Ducts
• ISSN:
  1545-9624
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article ; Journal Article
• Place as Subject:
  OSHA Region 3 ; 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
• Volume:
  4
• Issue:
  10
• NIOSHTIC Number:
  nn:20069899
• Citation:
  J Occup Environ Hyg 2007 Oct; 4(10):751-761
• 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:
  2008
• 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-512:0cca08a777c28e99662e61241f53a97544501ec040a5aef13865614e8a055fdbab103a34b617923db0ab2fad5e3065afb8637940871f63c62c9e8fd8b0d04e22
• Download URL:
  https://stacks.cdc.gov/view/cdc/208234/cdc_208234_DS1.pdf
• File Type:
  [PDF - 795.33 KB ]