Improving Communication in Noise When Wearing Hearing Protection

Details

• Personal Author:
  Brammer A
• Description:
  It is widely recognized that many workers in noisy occupations are unwilling to wear hearing protection because they fear they will be unable to talk to co-workers or hear warning sounds. The development of specialized hearing protectors that contain electronics to adjust the amount of hearing protection in order to increase the audibility of sounds when noise levels are low aids this situation. We wanted to improve communication when noise levels are high as well as low, and in this project have been developing algorithms for this purpose that could operate in hearing protectors equipped with suitable electronics (eHPDs). The methods developed are thus intended to enable speech and warning sounds to be heard in almost all situations, and hence reduce errors in communication between workers and the risk of injury to the user of the eHPD. The methods involve digital signal processing and were developed in MATLAB. First, band-pass filters separate sounds into parallel contiguous subbands, each with bandwidth approximately 1.5 times the effective rectangular bandwidth of the cochlea. The overall bandwidth is 200 Hz - 6 kHz and there are 16 subbands. The number of subbands and band-pass filter characteristics are chosen to enable future implementation in a stand-alone wearable device to be worn throughout a workday. The signals in each subband are separated into the sounds from outside the hearing protector to be processed, and a control signal derived in the time domain from the envelope of these sounds. Two methods for controlling the gain applied to individual subbands have been developed: in the first, the envelope is used directly to amplitude modulate the sounds from outside the hearing protector (called here direct modulation); and, in the second, the control signal switches the gain applied to a given subband on or off (so-called binary masking), depending on whether the sounds in the subband contain mostly those desired to be heard (switch "on") or undesired noise (switch "off"). After this process, the processed sounds from all subbands are combined, and the resultant audio signal is recorded so that it can be replayed to subjects. We ask people with normal hearing to come to our laboratory to listen to the audio files. The files contain standardized groups of similar sounding words spoken in noise that are chosen to confuse the listener, who must select only one from each group (e.g., select one word from - "kit", "bit", "fit", "sit", "wit", or "hit"). This test of consonant confusion, the Modified Rhyme Test, was selected to assess the performance of our algorithms as we believe it best represents the conditions under which critical communications and warnings will need to be understood, and so represents the best listening test for maintaining occupational safety. The response of our algorithms to warning sounds, such as vehicle backup alarms, is assessed numerically by the signal-to-noise ratio (SNR) of the alarm sound to that of the environmental noise, as this is known to be related to the audibility of the warning sound. [Description provided by NIOSH]
• Subjects:
  Electrical Equipment And Supplies Hearing Hearing Loss, Noise-Induced Noise Noise, Occupational Occupational Health Safety
• Keywords:
  Auditory Protection Electronic Equipment Hearing Conservation Hearing Protection Noise Exposure Noise Induced Hearing Loss Protective Measures Sound Wearable Technologies
• Series:
  Grant Final Reports
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Final Grant Report
• Place as Subject:
  Connecticut ; OSHA Region 1
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  OEP - Office of Extramural Programs
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-11
• NIOSHTIC Number:
  nn:20065787
• Citation:
  Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, R21-OH-011552, 2022 Jan; :1-11
• Contact Point Address:
  Anthony Brammer, PhD, University of Connecticut School of Med/Dnt, 263 Farmington Ave, Farmington, CT 06030-5335
• Email:
  brammer@uchc.edu
• Federal Fiscal Year:
  2022
• Performing Organization:
  University of Connecticut School of Med/Dnt
• Peer Reviewed:
  False
• Start Date:
  20180930
• Source Full Name:
  National Institute for Occupational Safety and Health
• End Date:
  20200929
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:c249b29280ea80d9d98ee0f63282ad7ae4139d96a3a3b6025a18db253ffad88b2fc4e460f2f83e6cc6eaf639143be5021caca71600a5bbe2aefbe2afd8acd6eb
• Download URL:
  https://stacks.cdc.gov/view/cdc/219124/cdc_219124_DS1.pdf
• File Type:
  [PDF - 1.10 MB ]