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March 16, 2007 7:32 AM CDT

Sound Management Technologies


According to industrial audiologist Brad Witt, the days of striving to develop hearing protection devices (HPDs) that could simply block the most sound are over. "Today, the focus is definitely more on sound management - on attenuating the hazardous noise to a level that still allows communication and warning signal detection," said Witt, who is audiology and regulatory affairs manager for the Bacou-Dalloz Hearing Safety Group.

"In noise-hazardous environments, we are not trying to eliminate all sound," Witt said. "There are still sounds we want to hear, such as co-worker voices, warning signals, mobile radios and even some machinery noise that may alert us to malfunction or maintenance needs. Wearing high-attenuation protectors without regard to communication creates a feeling of hazardous isolation, being cut off from the verbal and audible cues that keep us safe and connected with our work."

In response, Witt said, HPD manufacturers are increasingly working to develop more innovative products that protect without compromising these basic communication needs. One way this has been accomplished, according to Witt, is by designing HPDs with "flatter" attenuation characteristics.

"First-generation earplugs and earmuffs were not so effective against low-frequency noise, but attenuated high-frequency noise quite easily. These ski-slope attenuation curves created a distorted sound while wearing HPDs, making speech difficult to understand."

In contrast, newer generations of hearing protectors have raised low-frequency attenuation significantly, nearly matching the high-frequency attenuation. "This flatter attenuation curve creates a sound while wearing HPDs that is more natural," Witt said. "It still blocks the noise, but with less distortion of speech and warning signals. The effect is most noticeable for workers who have some existing hearing loss, even a mild loss."

Another innovative approach to managing the sound in loud environments is through sound amplification earmuffs. "How many times have we seen workers remove their earplugs to hear a radio call, or lift up their earmuff to talk to a co-worker?" Witt asked. "Sound amplification earmuffs have microphones, placed directionally on the ear cups, which amplify normal sounds to a safe level, while still protecting [wearers] from the hazardous workplace noise. The result is that workers have more control over hearing what they need to hear, without compromising protection."

Witt predicts this trend will guide new product development for several years to come. "We are just now beginning to take full advantage of recent advances in material and manufacturing technology that make these new approaches to hearing protection possible and economically viable," he said. "This, in turn, has sparked new developments in the design of these systems so we can better control not only how much, but the manner in which sound reaches the human ear."

But new technology is not the only way safety officers are seeking to "manage" sound in their workplace environments. "One of the simplest things they can do is provide HPDs with a range of attenuation ratings (NRRs)" said Witt. "By targeting attenuation to the level of the noise hazard, workers can be assured of adequate protection, while not totally blocking their ability to hear and communicate on the job."

Carrot More Effective Than the Stick
Knowing what safety precautions need to be followed and getting workers to follow through can be a tough sell.

"The word 'motivation' does not appear in OSHA's regulations on hearing conservation," Witt said. "But the safety-savvy employer will know motivation is the keystone to preventing noise-induced hearing loss. Motivated employees take responsibility for protecting their hearing both on and off the job, rather than just viewing hearing protectors as a workplace compliance issue."

Witt said there are three ways to instill the level of risk awareness that motivates workers to take proper defensive action by wearing their hearing protectors.

"First, is to dispel their illusion of invulnerability," Witt said. When it comes to ignoring hazardous noise, it's not only the young who feel invulnerable. Even seasoned workers will claim that the loud noise does not bother them because they are "accustomed" to the noise. While the brain may grow accustomed to constant noise, anatomically, the ears can never "toughen up" against hazardous noise. Ears respond by losing hearing.

Dispelling the invulnerable illusion can be done in several ways, Witt explained. One of the most effective is to show workers exactly how noise affects them. "Several studies have found that the incidence of noise-induced hearing loss drops significantly when workers are provided a copy of their annual audiometric tests, with an explanation of the results. It is hard to argue with an objective test that historically shows the progression of hearing loss from year to year."

Demonstrating "future risk" is the second method Witt suggested for bringing home the need for hearing protection. "We live in a culture of the 'here and now,' but noise-induced hearing loss displays no visible signs of injury and typically develops over years of exposure," Witt said. Many employers use audio demonstrations to simulate hearing loss, so that the worker has a clear understanding of the future risk and the need for adequate protection today.

A cheaper, yet equally effective tool is to have employees talk to older workers who have suffered hearing loss and regret their disregard for hearing protection.

The third motivating tool Witt recommends is to remove the barriers to wearing hearing protection. "This can be as simple as ensuring an adequate supply of earplugs by installing dispensers, but oftentimes the barriers run deeper," Witt said. Studies have shown that workers resist wearing hearing protection if the devices are not comfortable, or if they interfere with communication and job performance. Offering workers earplugs that don't overprotect and isolate the worker, as well as provide a comfortable fit can combat this.

"Unlike other occupational injuries, noise-induced hearing loss causes no pain or visible trauma," Witt said. "It is unnoticeable in its earliest stages, and generally takes years to diagnose. By showing these workers their susceptibility to noise damage, demonstrating the future risk, and removing the barriers to proper wearing of hearing protection, an employer invests in a workforce that takes responsibility for their own hearing protection, both on and off-the-job."

About the Author

Bacou-Dalloz is the world's largest supplier of personal protective equipment. Learn more at


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