But governments all over the world based ultrasonics-related regulations on those studies, Leighton said. The problem with those 1970s studies, Leighton said, is that they were conducted mostly on adult men, many of whom worked in loud jobs and likely had fairly weak hearing. (Anyone who was in high school in the late 2000s will likely remember the annoying "mosquito" ringtone that teenagers could hear but teachers generally could not.) And men tend to lose their hearing in those ranges before women do, according to most research into hearing loss.
Just about everyone loses some hearing at the high end of the spectrum as they age. (But I can't say for certain that this isn't the result of my headphones maxing out, rather than my hearing.)īut it's not too high for all humans to hear. I'm a 26-year-old man, and I can't hear anything once the tone rises past about 16 kilohertz. In the video below, a tone slowly rises from a superlow 20-hertz tone to a 1,000-times-higher 20 kilohertz. That's a very high-pitched sound - much higher than most adults can hear. Based on those studies, governments around the world arrived at a common guideline for ultrasonics in the workplace: 20 kilohertz at medium volumes, or 20,000 vibrations per second. But why can't everyone hear these sounds?īack in the late 1960s and early '70s, researchers for the first time systematically examined what sort of sounds could cause problems in the workplace but were high-pitched enough that they didn't become problematic in limited, low-volume doses. Rather, ultrasonics are likely exposing a large, young, vulnerable fraction of the population to discomfort, annoyance and the stigma of hearing things others can't. In reality, Leighton said, the reason ultrasonics are a problem is not that in bizarre, extreme cases they might expose a tiny fraction of the population to brain or permanent hearing damage. (Leighton, like most scientists, is skeptical that ultrasonic weapons were actually involved in that event.) And although the claim hasn't held up under scrutiny, that was perhaps not entirely nutty the most severe symptoms of ultrasonic-wave exposure do include headaches, tinnitus and hearing loss similar to what the U.S. The most famous supposedly ultrasonic event occurred when American diplomats in Cuba suffered a strange constellation of symptoms that officials initially attributed to some sort of ultrasonic weapon. Still, Leighton is one of a handful of experts on the subject, and he has no idea how many people are impacted by ultrasonics or how severe the effects are on a population scale. But it's backed up by decades' worth of consistent experiments by a number of different researchers. The illness in response to ultrasonic exposure might sound spooky to the point of superstition or quack theory, and researchers don't understand quite why it happens. "If you're in the zone and you're one of the sensitive people, you'll get headaches, nausea, tinnitus and ," Leighton said.
"So it dawned on me that we were putting ultrasound into public places where a minority but a large number of people are going to be affected." "These are places where you might have a footfall of 3 or 4 million people a year," he said.
While he couldn't hear the sounds, he recorded them using his microphones and consistently found ultrasonic frequencies. Leighton started his early work on ultrasonic waves by going to buildings where people reported having symptoms. But most acoustical researchers just aren't studying high-frequency sound in human spaces when Live Science reached out to a number of acoustics experts outside Leighton's immediate circle of colleagues for comment on this article, the vast majority said they didn't have the knowledge to comment. That isn't to say that Leighton's work is outside the scientific mainstream he was one of two co-chairs of an invited session on high-frequency sound at the ASA meeting and has received The Royal Society's Clifford Paterson Medal for separate research into underwater acoustics. "And that's, I think, why many sufferers ended up at my door." "I think you'd be lucky to find even six people around the world working on this," Leighton said.
0 kommentar(er)
