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5 Sounds You Probably Can't Hear

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Think you have perfect hearing? There are still plenty of sounds in the world that you can’t detect. The low range of human hearing starts around 20 hertz, and tops out at about 20,000 [PDF]. By contrast, bats can hear ultrasonic sounds with frequencies up to 110,000 hertz. Other animals, like elephants, hear sounds many times lower than those a human can perceive. And as people age, their hearing gets even worse, eliminating even more sounds from the range of audible noises. Here are just a few sounds most people are missing out on: 

1. Sounds for young people 

As humans age, their hearing changes. Age-related hearing loss, called presbycusis, means that older people can’t hear some high-pitched sounds they would have heard in their youth. Most people over the age of 18 cannot hear the 17,400 hertz tone in the video above. 

2. Music designed for cats

In 2014, activists from Pussy Riot rigged an electric piano to play music designed specifically for cats. Cats possess ultrasonic hearing, meaning they can hear a much wider frequency of sounds than humans (or most other mammals, for that matter) can [PDF]. Although people could hear portions of the concerto Pussy Riot staged to protest Internet censorship, the melody is a whole lot more complex from the feline point of view. For what it's worth, the cats seemed to enjoy it. Research has shown that cats are pretty into feline-specific tunes, in general. (We have some video evidence.) 

3. A dog-specific Beatles’ song

In the Beatles’ song “A Day in the Life,” the band included a whistling noise at a frequency of 15,000 hertz right after the last chord of the song, designed to be heard by canine Beatles fans. “We’d talk for hours about these frequencies below the sub that you couldn’t really hear and the high frequencies that only dogs could hear. We put a sound on Sgt. Pepper that only dogs could hear,” Paul McCartney told the BBC in 2013. (The sound starts just after the 5-minute mark.)

4. Ultrasonic finger friction

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When you gently rub your thumb and index finger together, the friction creates an ultrasonic signal [PDF]. The action is a useful way to test out the function of a bat detector, which converts ultrasonic sound from bat echolocation into noise humans can hear. In the book Insects Through the Seasons, entomologist Gilbert Waldbauer writes that pet bats can be trained to respond to the sound, and fly toward it. 

5. Infrasonic elephant calls 

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Elephants can hear and make sounds well below human range, to as low as 14 to 16 hertz. They can also produce these infrasonic calls at extremely high volumes, around 85 to 95 decibels. For comparison purposes, 95 decibels is the equivalent of the noise of a subway train from 200 feet away. These loud, low sounds allow elephants to keep in touch with each other over distances of more than a mile. Listen to an example of these elephant rumbles from the Elephant Listening Project

See Also: 9 Strange Sounds No One Can Explain

[h/t: reddit

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holidays
Bleat Along to Classic Holiday Tunes With This Goat Christmas Album
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Feeling a little Grinchy this month? The Sweden branch of ActionAid, an international charity dedicated to fighting global poverty, wants to goat—errr ... goad—you into the Christmas spirit with their animal-focused holiday album: All I Want for Christmas is a Goat.

Fittingly, it features the shriek-filled vocal stylings of a group of festive farm animals bleating out classics like “Jingle Bells,” “Rudolph the Red-Nosed Reindeer,” and “O Come All Ye Faithful.” The recording may sound like a silly novelty release, but there's a serious cause behind it: It’s intended to remind listeners how the animals benefit impoverished communities. Goats can live in arid nations that are too dry for farming, and they provide their owners with milk and wool. In fact, the only thing they can't seem to do is, well, sing. 

You can purchase All I Want for Christmas is a Goat on iTunes and Spotify, or listen to a few songs from its eight-track selection below.

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Animals
If You Want Your Cat to Poop Out More Hairballs, Try Feeding It Beets
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Have you ever wondered if there’s a way to get your cat to poop out its hairballs instead of hacking them up? If so, you’re likely a seasoned cat owner whose tolerance for gross stuff has reached the point of no return. Luckily, there may be an easy way to get your cat to dispose of hairballs in the litter box instead of on your carpet, according to one study.

The paper, published in the Journal of Physiology and Animal Nutrition, followed the diets of 18 mixed-breed short-haired cats over a month. Some cats were fed straight kibble, while others were given helpings of beet pulp along with their regular meals. The researchers suspected that beets, a good source of fiber, would help move any ingested hair through the cats’ digestive systems, thus preventing it from coming back up the way it went in. Following the experiment, they found that the cats with the beet diet did indeed poop more.

The scientists didn’t measure how many hairballs the cats were coughing up during this period, so it's possible that pooping out more of them didn’t stop cats from puking them up at the same rate. But considering hairballs are a matter of digestive health, more regular bowel movements likely reduced the chance that cats would barf them up. The cat body is equipped to process large amounts of hair: According to experts, healthy cats should only be hacking hairballs once or twice a year.

If you find them around your home more frequently than that, it's a good idea to up your cat's fiber intake. Raw beet pulp is just one way to introduce fiber into your pet's diet; certain supplements for cats work just as well and actually contain beet pulp as a fiber source. Stephanie Liff, a veterinarian at Pure Paws Veterinary Care in New York, recommends psyllium powder to her patients. Another option for dealing with hairballs is the vegetable-oil based digestive lubricant Laxatone: According to Dr. Liff, this can "help to move hairballs in the correct direction."

[h/t Discover]

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