According to industrial audiologist Brad Witt (pictured), the days of striving to develop hearing protection devices (HPDs) that could simply block the most sound are over. “Today,” said Witt, who is audiology and regulatory affairs manager for the Bacou-Dalloz Hearing Safety Group, “the focus is definitely more on sound management: on attenuating the hazardous noise to a level that still allows communication and warning signal detection.
“In noise-hazardous environments, we are not trying to eliminate all sound,” he adds. “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 ear plugs and ear muffs 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 which is more natural,” said Witt. “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 ear muffs. “How many times have we seen workers remove their ear plugs to hear a radio call, or lift up their ear muff to talk to a co-worker?” Witt asked. “Sound amplification ear muffs have microphones, placed directionally on the ear cups, which amplify normal sounds to a safe level while still protecting 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 which 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.”