Hearing Through the Protectors
How hearing protection changes speech understanding and what to do about it.
Continued from page 8 • Hearing-impaired listeners wearing hearing protection: results are not as definitive, however suggest, • SD is unchanged in high noise levels, greater than or equal to 85 dBA • SD is worse in low-to-moderate levels of background noise, 80 dBA or less.
Hearing Protector Effects on Speech Discrimination Low Sound Levels < 80 dBA Moderate Sound Levels About 80 dBA High Sound Levels > 85 dBA Decreased Unchanged Improved Decreased Decreased Unchanged
• Hearing protector type Studies aren’t extensive enough to differentiate SD differences based on the type of hearing protector. However hearing protection type is a factor in the ability to localize sound. Finding a sound in open space depends on subtle differences in amplitude and timing between when the sound reaches the right and left ears. Maintaining the natural state of the outer ear is important to receiving these clues. Earplugs, which only occlude the earcanal, have less of an effect than earmuffs that block the entire outer ear. If localizing sound is critical to job performance, earplugs are generally a better choice than earmuffs. Tactics for improving speech communication in noise Based on the information already discussed, how can an employer help workers improve speech communication in a noisy work environment? The tactics discussed here presume the employees are wearing hearing protection.
• Teach employees to speak more loudly and distinctly To compensate for the occlusion effect and the tendency to speak quickly in noise, instruct employees that speaking LOUDLY and CLEARLY (more loudly than they think they need too) is critical to understanding. It is most helpful for the speaker to make these accommodations; the listener should not be removing hearing protection. • Know the background noise Remember that speech understanding becomes poorer for persons wearing hearing pro- tectors as background noise levels decrease. Hearing protection isn’t generally needed in environments less than 80 dBA, and if used, may jeopardize communication and safety. However in moderate-to-high noise environments, speech understanding can improve. Ensure that employees are properly using hearing protection in noise at 85 dBA and higher. • Use visual clues for speech whenever possible Teach employees to watch the speaker’s face. The listener can watch the lips and facial expressions of the speaker to supplement the auditory information, ultimately increasing understanding. Use hand gestures when possible. • Develop key words or phrases specific and meaningful to the work environment Most jobs have repetitive cycles and use language specific to the job task. Work with employees and supervisors to identify specific words or short phrases that can convey the same information as longer messages. Train employees to substitute “code” words. For example: “go fiber 3” might be substituted for “deliver packaging supplies to Building- 3 fiber room. Develop a “wait & hear” approach to verify communication takes place before the employees leave. • Practice makes perfect Research has shown that employees who routinely work in noise will adapt to the poor listening conditions, and eventually outperform inexperienced subjects. Because of the brain’s plasticity, it has the ability to adapt its neural connections. Thus, with time it can learn to fill in the gaps for what it doesn’t hear by integrating all the information - visual, contextual, and behavioral - so that SD can improve with experience. Encourage new and seasoned employees to work together. • Increase the signal-to-noise ratio Understanding speech becomes easier as the speech signal becomes louder than the back- ground noise. Specialty hearing protection devices are available that amplify speech while limiting the output to a safe level. These are particularly useful in intermittent noises and for hearing-impaired workers or for jobs where communication is critical.
• Use visual or vibrotactile alerting systems When hearing is difficult, add vision. Flashing lights, colored light sequences, etc., can supplement or be substituted for horns or beepers. Cell phones on vibrate mode and text messaging may also be helpful for alerting workers, particularly those with hearing loss. • Develop individual plans for hearing-impaired workers Recognize employees with hearing loss who may need special accommodations. Often the professional supervisor (audiologist or physician) of the audiometric testing portion of the hearing conservation program can be a resource for developing plans for individ- ual workers with hearing loss. For more information, refer to Occupational Safety and Health Administration Safety and Health Information Bulletins: Hearing Conservation for the Hearing Impaired Worker at
http://osha.gov/dts/shib/shib122705.html and Innovative Workplace Safety Accommodations for Hearing Impaired Workers at
http://osha.gov/dts/shib/shib072205.html. •Develop a job-specific protocol for determining auditory needs Some jobs require more critical communication capabilities than others. There is no “one-size-fits-all” approach to determining what hearing criteria should be applied or how employees should be evaluated for hearing/communication ability. Key to develop- ing a protocol is to investigate the job tasks, employee responsibilities, and the work environment for each job. Next, the individual employee’s hearing ability should be con- sidered. Some situations will require evaluation beyond pure-tone hearing tests and an audiologist may need to be consulted (Tufts, 2009). Examples of hearing protection con- siderations include use of earplugs rather than earmuffs when sound localization is imperative, and use of lower-attenuation devices rather than higher-attenuation devices when background noise is low.
“Is it reasonable to expect my employees to hear the sounds they need while they are wearing hearing protection?” Clearly, employers and employees both win if the answer to this question is a resounding “Yes!” To achieve this definitive answer, each individual case should be considered regard- ing noise exposure, hearing protection, the job tasks specific to communication needs, and the individual employee’s ability to perform them. Many times, simple modifications such as fitting hearing protection appropriately and teaching employees better communication strategies can be made to enhance communication while reducing the risk of hearing loss from hazardous noise. When hearing-critical jobs are identified, more elaborate investigation may be needed. Employees who consistently remove hearing protection in order to hear are essentially giving a cry for help. Can you hear it?
References Berger, E. H. (1980). “EARLog #3 – The effects of hearing protectors on auditory commu- nications,” Sound and Vibration 14( 1), 16-17, provides references for the findings in this paper. It is available at
www.e-a-r.com/hearingconservation/earlog_main.cfm Tufts, J.B., Vasil, K.A., and Briggs, S. (2009). “Auditory fitness for duty: a review,” J. Am. Acad. Audiol. 20( 9), 539-557.
Elliott H. Berger, M.S., is a Division Scientist for 3M’s Occupational Health & Environmental Safety Division. For over 30 years he has studied noise and hearing conservation with an emphasis on hearing protection. He chairs the ANSI working group on hearing protectors, has been lead editor for two highly-regarded texts in noise and hearing conservation, served on a National Academy of Science committee evaluating hearing loss in the military, and has presented his research in numerous text book chapters and over 60 published articles.
American Academy of Audiology
www.audiology.org Council for Accreditation in Occupational Hearing Conservation
www.caohc.org E-A-R Hearing Conservation Educational Page
www.e-a-r.com/hearingconservation/ National Hearing Conservation Association
www.cdc.gov/niosh/topics/noise/ OSHA etool: Noise and Hearing Conservation
Hearing Conservation Resources