Time to read: 15 minutes
Human hearing is pretty impressive all things considered.
Our hearing kicks in at about 20Hz and tops out at 20,000Hz, although the bulk of the sounds we process fall in the 2000-5000Hz range.
We have two ears which work in concert with our brain to work out the direction and distance a sound is from us. They are also integral in helping us manage our balance and spatial awareness.
But over time the range of sounds we can hear is reduced. And that reduction begins as young as eight years.
Over the age of 40, men have approximately 5 to 10 dB greater loss in the upper frequencies and when that decline continues, it is important to be tested and wear hearing aids if prescribed.
But as good as our hearing is, animals have a far more impressive range.
Let’s take a look at the top 10:
Pigeons have incredible hearing and there is some scientific speculation that they use their exceptional ability to hear infrasound as part of their impressive in-built navigation system. Infrasound simply means sound waves with frequencies that fall below what humans can hear.
Pigeons incredible ability to navigate and first their way home has been invaluable during war time, so much so The founder of the PDSA (People’s Dispensary for Sick Animals), Mrs Maria Dickin, instituted the PDSA Dickin Medal. This is awarded to any animal displaying conspicuous gallantry and devotion to duty. Of the 53 Dickin Medals presented during World War II, 32 went to pigeons.
Pigeons excel in the lower frequency range but rats rule the higher frequencies. Rats hear sounds up to 90,000Hz and they chat to their young at frequencies around 50,000 Hz - which is far higher than we can detect with our ears.
Did you know that rats can giggle when tickled? Pet rats love to receive belly tickles and will actively seek out more. They will also behave dogs and cats who are ready to play with a particular type of frolicking that scientists have dubbed Freudensprünge, or “joy jumps”.
Horses can hear quite a bit better than humans. They can detect sounds at a lower frequency 14Hz (compared to 20Hz) and up to 2500Hz (2000 Hz for humans). But more than that, horses have 10 muscles in their ears which allows them to move 180 degrees. We humans have only three muscles in our ears.
Another thing which distinguishes horses from humans is they don’t appear to suffer from age-related hearing loss like humans do.
Given elephants have such big ears, it shouldn’t be a surprise that they have good hearing. Their hearing excels in the higher frequencies six times higher than humans at 12,000Hz.
Their ears also help them keep cool. In the hot climates where they live, the large surface area and thinness of the ears help regulate the mammal’s body temperature, keeping it cooler for longer.
They can also hear the calls of other elephants up to 4km away.
Dogs can identify sounds 800 metres away which means they can hear the sound of your car returning home and be right there at the front door with tails wagging to greet you.
Their average hearing range is between 67 Hz to 45,000 Hz. That high end frequency perception is why ultrasonic whistles have been used as part of training. Doggie hearing is so acute, it can pick up the high-frequency pulse of the crystal resonator used in digital alarm clocks and even bodily vibrations of termites in the walls!
The ears are a big part of how dogs express themselves. Erect ears facing forward indicate interest and alertness. Slightly pulled-back ears are a sign of friendliness, while ears laid tightly back against the head suggest a fearful or timid reaction.
Cats rule! Not just as a matter of course, but also on the hearing league table too. They can hear lower frequencies and higher frequencies better than dogs. They also have about three dozen muscles controlling their ears to give them a 180-degree coverage.
Cats also engage with music and have very specific preferences related to the sounds they like to hear like purrs and the chirping of birds. The Smithsonian Magazine has a fascinating article on this and an example of a cat concerto!
Dolphins use echolocation to hear - just like bats. Their super power is in the higher frequencies where they can hear sounds to 20,000Hz. By contrast, whales use low frequencies to communicate.
You might be surprised to hear that the ocean is a noisy place. Not only are the animals talking to one another, there is also the sound of submarines, ship engines, underwater drilling, blasting and more.
Researchers in the Netherlands and Russia have discovered dolphins have learned to reduce their hearing by 10-20 decibels at will to protect themselves from loud sounds.
The scientists measured the animals’ brain activity while hearing sounds loud enough to evoke a response, but below the threshold of causing temporary hearing loss. Each of the trained captive animals learned to reduce its hearing sensitivity by 10 to 20 decibels when the scientists played a warning signal before producing the loud sound, the researchers report in a paper in press at Integrative Zoology.
“That’s similar to a human putting in foam earplugs,” says team leader Paul Nachtigall, a marine biologist and director emeritus of the Marine Mammal Research Program at the Hawaii Institute of Marine Biology in Kailua. “It’s really fascinating to be able to have that switch inside of your head.
Owls are avian champions with exceptional hearing ability as well as outstanding vision.
A barn owl hearing ranges from about 200 Hz up to 12,000Hz. By comparison, a parakeet can hear up to 8000Hz and the chicken only hears high frequencies as high as 2000Hz.
A bird's ear openings are actually located behind and slightly below its eyes. In owls, one opening is higher and one is lower to aid in locating prey at night. Because of the difference in the location of the openings, an owl will hear a sound at two slightly different times. The owl uses that very small difference – a 3 microseconds - to pinpoint the location of its prey.
Even the owl’s slightly concave fact is optimised for collecting and directing sound to its ear openings.
Bat can hear in the range of 9000 Hz to to 200,000 Hz. And the sounds they make are incredibly loud indeed! Some species of bats call as loud as 120dB (equivalent to a pneumatic drill). That call would seriously harm human hearing, but fortunately the sound is in the ultrasonic frequency so we don’t detect it at all.
Bats are also extremely sensitive to miniscule changes in frequency. This an important tool as hearing is a bat’s primary sense. Blind as a bat is an absolutely true saying!
But it is the creature with the most simple ear structure which has the best hearing of all animals in the animal kingdom (that we know of so far).
The Greater Wax Moth (Galleria mellonella), found in most places in the world (and considered a pest here in Australia) is capable of hearing frequencies up to 300,000Hz (300kHz).
Moths have a pair of eardrums on its flanks that each vibrate four receptor cells but that is enough to alert them to potential predators. The Greater Wax Moth is particularly well adapted to avoid bats with their exceptional hearing.
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