“There’s such an enormous range of abilities and loudness in animals, it’s very easy to get swept up by it all. I just love this stuff,” said bioacoustician Christopher Clark of Cornell University.
While every animal sound is amazing in its own right, the result of millions of years of evolution, Clark and other researchers have a few favourites. In this gallery we review the best, and look at the physics that produce them.
While not one of the loudest animals on the Earth, lions’ 115-decibel calls travel as far as 8km across the Serengeti.
Sound: San Diego Zoo
Though inaudible to human ears, their infrasonic calls can travel more than 1600km in the open ocean and can make nearby boat hulls resonate.
Their rumbles can top 188 decibels. The decibel scale is a measure of sound intensity that jumps 10-fold in energy for every 10 decibels.
Loudness in the water, however, isn’t the same out of it. “If you try waving your arms in air, it’s easy. Air is flimsy and not very dense. It takes more work to propagate sound in water,” Clark said.
A generally accepted water-to-air conversion is to subtract 62 decibels, making blue whale calls equivalent to 126 decibels in air – about as loud as an amped-up rock concert.
Counter to popular notions, however, blue whales are not the loudest creatures. Researchers in 2003 reported a 236-water-decibel bellow from a sperm whale.
Special microphones can measure the pressure waves of such impossible-to-hear sounds, allowing us to compare their “loudness” to audible sounds.
Also called pistol shrimp, these crustaceans unleash the most intense sounds in nature.
An over-sized spring-loaded claw produces a 200-decibel snap lasting for just one millisecond. The snap is so loud and intense that it momentarily heats a small area of water to temperatures hotter than the sun’s surface.
Called cavitation, the following implosion of plasma emits light and creates shock waves able to stun small and unwary prey. The sounds frustrated early submarine engineers, as the pops interfere with sonar readings.
“Their sound dominates all oceans of the world. It’s like an incredibly potent popcorn going off,” said organismal biologist Sheila Patek of the University of Massachusetts Amherst.
The clicks and squeals of dolphins are more than cute communication. Their entire head is a fine-tuned biological sonar machine that allows them to see in pitch-black waters.
“These are very brief but very intense high-frequency sounds. It’s like they have a laser beam or a strobe light coming out of their forehead,” Clark said. “It’s designed to illuminate their environment and get images back.”
A chamber in their rounded forehead, called the melon, emits the ultrasonic pulses. Fat-filled jaw bones conduct the echoes to their ears. Although outside the range of human hearing, some species’ echolocation calls peak around 220 decibels.
Clicks, whistles and other audible sounds (listen below) often accompany the higher-pitched and inaudible noise of echolocation.
Similar to whales, elephants can communicate with rumbles that dip below the lower end of human hearing, which is roughly 20 hertz (our hearing tops out at a high-pitched 20,000 hertz).
Elephant rumbles can exceed 117 decibels in the air – comparable to a football stadium full of cheering fans, but inaudible to us – making elephants perhaps the loudest land animals on Earth.
The soundings can travel more than 10km in open air,. They are ultimately felt through the trunks, skin and feet of listening elephants.
Some species’ howls can be heard through thick Central and South American jungle cover from more than 5km away.
Researchers think howler monkey troops use the vocalisations to announce territorial borders and avoid competition for food.
The frumpy-looking creature uses the muscles to vibrate their swim bladders, producing grunts and hoots. Some species’ territorial and mating calls are so loud in water (129 decibels) that they can be heard on land.
“A few decades ago, people near San Francisco Bay thought they heard a Soviet submarine attack underway, and they called the police,” Patek said. “It turned out toadfish were making the sounds.”
The strange calls also contain an extra layer of complex information, perhaps allowing for richer communication than was thought possible in the fish.
Image: A transparent view of a toadfish. The two-chambered swim bladder is seen at centre between the animal’s fins. (Aaron Rice)
Sounds: The hoots and grunts of a three-spined toadfish. (Aaron Rice)
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