The second biggest cause of hearing loss in the United States is noise, much of it produced in the workplace. Preventing that noise from damaging a worker’s hearing has been the mission for some 30 years of earplug maker Howard Leight Industries in Smithfield.
Leight, along with a Swedish company called Bilsom, form the hearing safety group of the Bacou-Dalloz Cos. based in San Diego. Originally, hearing safety experts sought to block – blocking as much sound as possible. But in recent times, they’ve modified their thinking, adopting a more holistic sound management approach.
The Providence Business News spoke with Leight’s audiology and regulatory affairs manager, Brad Witt, about this and other trends in hearing safety technology.
PBN: The buzz in your industry now is all about “sound management.” What do you mean by sound management in noise attenuation devices?
WITT: The hearing protection industry is geared around blocking sound. That worked fine for the first few years. But we quickly found that blocking sound is only part of the equation.
There are certain sounds that we don’t want to block. There is hazardous noise out there, but there are sounds that a worker wants to hear – his communication radio, co-workers talking to him, a telephone, the public address system or a warning signal from a forklift backing up.
PBN: Has blocking too much sound been a barrier to greater use of noise attenuation devices in the workplace?
WITT: It definitely has. Workers will often compromise the fit of a hearing protector – back it out of the hearing canal a bit so it’s not protecting as much – so they can hear what they want to hear.
PBN: How has technology contributed to the better sound management of your attenuation devices?
WITT: With new materials, we can actually shape the attenuation curve. Hearing protectors can block the low frequency bass tones or the high frequency treble tones or something in between. We have a better ability to shape that response curve so it will favor certain frequencies more than others.
PBN: How do you shape attenuation? Through design? Through materials?
WITT: Both. We have an earplug now that looks like a normal earplug but it has a flat, or uniform, frequency response.
For years and years, conventional earplugs did two things: they turned down the volume for the listener, and they also turned down the treble control because they block more of the high frequencies than the low frequencies. That can be a real disadvantage because a lot of the cues we get for understanding speech are in the high frequencies. If someone tells you, “Tie your shoe,” without the high frequencies, it sounds like “I er oo.”
Now, with materials and design, there are earplugs that turn down the volume but don’t mess with the bass and treble controls.
PBN: Are there noise frequencies that we can’t hear that can harm us?
WITT: You see press reports about that sometimes, but in reality, we don’t worry about that too much because the vast majority of hazardous noise exposures are in that range that we can hear.
PBN: One industry that is notorious for hearing loss among its workers is the construction industry. Is that industry noisier than others?
WITT: It’s not so much noisier as much as there are some difficult challenges there. There are very intermittent noise levels in construction. If you work in a factory, noise will be constant all day so you know to use your hearing protection. In construction, you might be exposed to high noise levels, but you might be exposed to them for a minute or two at a time, so you might not bother to use your hearing protection.
Another problem is the misperception that if you use your hearing protection you won’t be as sensitive to hazardous warning signals on the site. Construction also doesn’t fall under the same OSHA regulations as general industry. In general industry, we have a clear standard about hearing protection. Construction is not the same.
PBN: There have been news reports about hearing loss attributed to digital music players. Apple has even been sued over the issue. You’re making an ear muff model with an AM/FM radio in it. Is there any concern that you may be contributing to hearing loss with something like that?
WITT: The decibel scale is a logarithmic scale. So 80 decibels plus 80 decibels doesn’t equal 160 decibels. It equals 83 decibels. Every three-decibel increase equals a doubling of the sound energy. When we make amplification and radio earmuffs that put sound into the ear, they have limiting filters built into the circuitry that cuts off at 82 decibels. So no matter how high you turn up the volume on that ear muff, the most you will get out of that radio earmuff is 82 decibels.
With the radio off, let’s say you enter a high noise level – 100 decibels of noise. The ear cups alone will block 20 decibels of noise. So without the radio on, your exposure is about 80 decibels of noise. When you turn on the radio, the most you’ll get out of that radio is 82 decibels. That combination of 82 decibels of radio noise and 80 decibels of outside noise gives you exposure of only about 84 decibels, which is still a very safe level.
Those radio earmuffs aren’t for everyone, but they’re safer than wearing an iPod at work.
