Industrial Hygiene News - July/August 2010

The classic scene Supervisor: Hey – you aren’t wearing your earplugs. That’s the third time this week! Employee: I know I know! But I just can’t hear Joe’s instructions! I had to take them out. It’s not my fault! This classic interaction is played out everyday in the workplace. Employees, who struggle to hear, may remove their hearing protection temporarily and some may simply stop wearing hearing protection altogeth- er. This response is likely to create a much bigger permanent communication problem: noise-induced hear- ing loss. In the meantime, worker complaints like this one may cause an employer to wonder:

“Is it reasonable to expect my employees to hear the sounds they need while they are wearing hearing pro- tection?” After all, it does seem a bit counterintuitive to block the same sounds the wearer is trying to hear.

Understanding how hearing protection changes sound is an important step towards ensuring employees are appropriately protected from hazardous sound without impeding their safety or productivity. Hearing pro- tection, worn properly, will decrease all sounds: both unwanted sounds (noise) and useful sounds such as speech and warning signals. With some attention, most communication issues can be resolved or at least improved. This article explains how hearing protection affects auditory communication and suggests approaches to overcoming difficult listening situations. The ears on overdrive The human hearing mechanism works most effectively at low and moderate sound levels. High sound lev- els, 85 dBA or greater, overdrive the auditory system and introduce distortion within the ear itself. Like the poor fidelity of overdriven speakers, overdriven ears cause signals to lose clarity, making speech difficult to understand. Wearing earplugs or earmuffs in a high noise environment is comparable to wearing sunglasses in intense sunlight. The filtering decreases the intensity and glare of bright sunlight to permit a more relaxed viewing experience. Like the photos in Figure 1, a day at the beach without sunglasses is harsh, causes squinting and perhaps a headache and early fatigue. But viewed through sunglasses the scenery is much more pleasant, the details easier to discern and the shadows and colors apparent. Likewise, hearing protec- tion reduces the overall sound input that reaches the inner ear, allowing the auditory system to work more comfortably and effectively. It takes two to communicate Wearing hearing protection causes other changes. First, is a phenomenon called the occlusion effect. When the ears are blocked or plugged, external sounds become softer, but internal sounds seem louder and “echo” inside the head. People describe their own voice as “booming” or like “talking in a barrel.” As a result, when wearing hearing protection, employees are likely to speak more softly. Secondly, people tend to talk more quickly when wearing hearing protectors in noisy environments. The combination of talking more softly and quickly has obvious implications; the listener has more difficulty understanding the speaker. In the opening scenario, the employee removed his hearing protection to hear better, however, the speaker is still talking less loudly and too quickly, and the listener is hearing the factory sound at high levels. The problem isn’t solved by removing hearing protection and will only become worse over time as hearing is damaged.

Figure 1 - Visual analogy demonstrating how sunglasses improve vision by reducing visual overload.

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HazMatShower.com 800/589-2849 Heath Consultants Inc. 800/432-8487 Hexarmor 616/459-4144 Honeywell Analytics 800/323-2000, www.honeywellanalytics.com ICx Technologies ; ; 800/391-4527 Idaho Technology Inc. ; 801/736-6354 Impacto Protective Products Inc. 613/966-0062, www.impacto.ca Industrial Scientific Corp. 800/338-3287, www.indsci.com INFICON ; 800/223-0633 Instinct Performance Hand 800/796-3235 International Medcom 707/823-0336 Interscan Corp. 703/796-6063 J. J. Keller & Associates Inc. 800/843-3174 Kappler Inc. 800/600-4019 Kimberly-Clark Professional 800/255-6401, www.kc-safety.com KWJ Engineering Inc. ; 800/472-6626 L P Royer Inc. 819/549-2100 Landauer Inc. 708/755-7000 Laurus Systems Inc. ; 410/465-5558 LIFE Corporation 800/700-0202, www.lifecorporation.com Magid Glove & Safety Mfg. Co. LLC ; ;; 800/444-8030 MAPA Professional 800/537-2897 MCR Safety 800/955-6887 MITI Mfg. Co. Inc. 866/545-6484, www.mitico.com Mil-Ram Technology Inc. ; 888/464-5726, www.mil-ram.com Mirion Technologies Dosimetry Services Division 800/251-3331 Moldex-Metric Inc. 310/837-6500 Morphix Technologies ; 800/808-2234 MSA ; 800/672-4678, www.msanet.com Nasco Industries Inc. 812/254-7393, www.nascoinc.com National Safety Apparel Inc. 216/941-1111 Nextteq LLC ; 877/312-2333, www.nextteq.com Occupational Health Dynamics 888/464-3872 Optics Laboratory 626/350-1926 Pelsue Company Inc. 303/936-7432 Photovac Inc. ; 781/290-0777 Protective Apparel Team 866/723-3212 Protective Industrial Products 800/262-5755 PureAire Monitoring Systems ; 847/726-6000 Quest Technologies, a 3M Company 262/567-9157 QRP Gloves Inc. 520/790-3533 Ritz Safety ;;;;;;; ; 800/451-3077 Ronco Protective Products ; 905/660-6700 RWC Testing & Lab Supplies ; 915/852-3375 S. E. International Inc. ; 800/293-5759 Safetec of America Inc. ; ; CR 716/895-1822