An estimated one-third of the US's three million farmers have some level of hearing loss caused by their inner ears' daily bombardment from sounds that can rival a rock concert's sonic impact. Even farmers still in their 20s can end up with the muffled hearing of someone in middle age if they fail to protect their hearing.
"You just can't get away from the machinery. We're driving those tractors and they're so goddamn loud," said Tom Duerst, a 55-year-old dairy farmer with partial hearing loss he attributes to farm noises he was exposed to in his youth.
Many farmers are on their own when recognising their elevated risk of hearing loss, because only the largest US farms operate under federal workplace safety regulations. Though the risks have been known for decades, only more recently have nonprofits, university researchers and federal agencies focused on trying to educate farmers and their children how to avoid hearing loss by wearing sound-cutting earmuffs or ear plugs.
Design changes in farm machinery, such as tractors, has made some equipment run quieter, but many still use older, noisier models. And livestock can still produce the same cacophony of noises; a squealing pig, for example, can be as loud as a running machine.
To nudge farmers to protect themselves, farm extension service educators often highlight sobering noise-impact facts at trade shows or conventions. And 4-H programs and some Future Farmers of America chapters use online resources to urge the next generation to wear ear plugs to ward off noises such as operating a tractor without a cab - which can damage hearing in only 15 minutes without protection.
Duerst recalls spending hours as a youth around rumbling tractor engines and loud milking machines on the 500-acre dairy farm he now co-owns.
"That was just normal when you were a kid. That was just life," he said. He is certain now those noises are the cause of his partial hearing loss.
In his late 20s, Duerst began using earmuffs during clay pigeon shoots. He realised the same equipment could protect his hearing when he operated an open-cab tractor. Now, all of the farm's tractors are equipped with headphones that are permanently attached by cords for convenience - and as a constant reminder to use them.
"We kind of stumbled into it and it's worked out well for us since then," Duerst said.
Grain farmer Charles Schmitt, a 63-year-old who farms more than 2,000 acres of corn and soybeans near the southwestern Indiana town of Haubstadt, said he also suffered hearing loss in his youth from exposure to tractors and other noises. He's worn ear plugs and earmuffs for about five years, as does his son.
Schmitt said most of the machinery he uses these days isn't as loud as earlier models.
"Sometimes you'll get a piece of equipment that's louder than it ought to be. It's a blast compared to what most people are used to," he said. "When it's loud we either stay a little farther away, or add to our hearing protection."
Implement manufacturers have started making quieter tractors and machinery. Deere & Co, the maker of John Deere tractors, has added sound-dampening panels to the roofs of their tractor cabs and incorporated sound-absorbing laminated glass and other features to help cut noise, company spokesman Ken Golden said.
While the general adult US population has seen improvements in hearing since the 1970s, when federal workplace safety rules began, the threat to farmers really only entered the spotlight in the past five or so years, said Gordon Hughes, director of clinical programs for the National Institute on Deafness and Other Communication Disorders.
Hughes said repeated exposure to noises in excess of 85 decibels - comparable to the sound of heavy city traffic - damages tiny nerve endings called hair cells inside the cochlea, the inner ear's pea-sized hearing organ.
"This is all cumulative, not just one day, but the next day adds more, the day after that adds even more. And farm activities tend to be repetitive," he said.
Hughes estimates more than a third of the nation's three million farmers likely have some level of noise-induced hearing loss, but notes that's a conservative figure as some research suggests nearly three-quarters of farmers have some level of hearing loss.
Billy Martin, an audiologist at Oregon Health & Science University in Portland, said more farmers than ever are aware of the risks, but many don't seem to recognise they can take steps to protect their hearing.
"The culture can be sort of like, 'Don't worry about it, it's just part of life and if you get hearing loss, well your grandfather had hearing loss and his father before him did - it's part of the deal'," Martin said.
Research published in 2006 found that 2700 male farmers from mostly Illinois, Indiana and Iowa showed dramatically higher levels of hearing loss between the ages of 20 and 60 than people who don't work in loud environments.
James Lankford, a now-retired professor of audiology at Northern Illinois University who co-authored the study, said many of those farmers already had hearing loss by their early 20s.
"The younger farmers, the ones who were going to take over the farm, realised how significant a hearing loss they could face by working without ear protections when they're around high-intensity noises," he said. "It was really enlightening for them."