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Dog whistles -

It has been proven that dogs can hear whispers of between negative five to negative 15 decibels. For perspective, a volume of zero decibels is considered the lowest limit of human hearing. 

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Dog whistles -

Also, dogs can hear frequencies as high as 45,000 hertz, which is almost double what a normal human ear can detect. 

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Tomato plants -

Plants are usually considered to be fairly quiet organisms. However, a 2023 study reported on how researchers placed tomato and tobacco plants under various levels of stress, such as denying them water or cutting them, and found that those plants under more stress actually emitted sounds.

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Tomato plants -

Does this mean that your tomato plants are trying to tell you to water them? Maybe, but the problem is that the plants are inaudible to people, since the sounds are ultrasonic.

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Bat echolocation -

These flying mammals use ultrasound to find their food. Bats do this by using squeaks and clicks up to 160 times per second, which range in frequency from 20 to 200 kilohertz. Known as echolocation, these sounds bounce off possible prey, mainly insects, so that bats can detect them. 

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Bat echolocation -

With the echo, bats can determine not just the location, but also the size and texture of their prey. Echolocation not only gives the bat the ability to hunt effectively at night, but it's also an incredible navigation aid.

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Whale song -

Whales have enchanted people for centuries, and what's even more fascinating is that these animals can vocalize and hear very low-pitched, or infrasonic, sound.

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Whale song -

Crucial for their survival, infrasound travels large distances underwater, giving whales the ability to call to one another across an ocean. 

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Acoustic weapons -

Acoustic weapons may emit audible and inaudible sounds that humans can't even hear. Research has shown that infrasonic weapons could cause nausea, vomiting, organ damage, and perhaps even death. 

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Acoustic weapons -

These types of weapons are still largely under study and development. However, long-range acoustic devices (LRADs) have been used by police in the US to disperse protesters by inflicting pain and nausea.

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Tiger roars -

A tiger's roar is known for paralyzing its victims. Still, there may be more to tiger sounds than just what humans hear. 

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Tiger roars -

Studies have shown that they produce not only the growls that we hear, but also infrasound down to 20 hertz, which they use to maintain their territory.   

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Ultrasonic finger friction -

When you gently rub your thumb and index finger together, the friction creates an ultrasonic signal.

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Ultrasonic finger friction -

By doing this, one can test out the function of a bat detector, which converts ultrasonic sound from bat echolocation into noise humans can hear. 

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Elephant rumbles -

Most of us are familiar with the trumpeting call of an elephant, but there's more to this familiar animal as a number of elephant sounds fall in the inaudible infrasonic range of between one and 20 hertz. 

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Elephant rumbles -

These unheard calls seem to be most often used by family groups to communicate, as well as to mark their territory. 

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Lightning bolts -

Lightning bolts are associated with thunder, but these powerful phenomena also produce sounds that humans can't hear. 

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Lightning bolts -

In one 2018 study, researchers found that one lightning strike generated infrasound in the 0.1 to 20 hertz range. 

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Giraffe noises -

To the human ear, giraffes are typically quiet animals. However, they are quite capable of generating infrasound using their anatomy.

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Giraffe noises -

They do this by stretching their long necks in an upward arc and pointing their heads up. Researchers believe that giraffes use infrasound to keep in touch with each other over long distances.

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Waterfalls -

One of the most emblematic sounds of nature, these natural wonders are so powerful that they also generate sounds beyond what humans hear.

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Waterfalls -

A study showed that the Niagara Falls emits powerful infrasound ranging from five to 20 hertz. Birds can hear these sounds from long distances, and it's believed that they use these sounds to help navigate during migrations.

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Volcanoes -

Volcanoes are so powerful that they release sound in the infrasonic range when they erupt. The eruption causes vibrations in the ground and pressure waves in the air. Those in the earth are seismic waves, while the pressure waves in the air translate to sound. 

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Volcanoes -

In order to keep watch over these potentially dangerous natural phenomena, scientists have established stations to monitor the infrasound emitted by erupting volcanoes.

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Mouse squeaks -

It's a known fact that mice squeak, but what you may not know is that you actually can't hear many of their squeaks. 

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Mouse squeaks -

Studies have shown that a mouse can squeak in the ultrasonic range of 30 to 110 kilohertz, which is impossible for our ears to hear. 

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Sounds for young people -

As we age, our hearing changes. Age-related hearing loss, called presbycusis, occurs gradually for many of us. 

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Sounds for young people -

This means that older people can’t hear some high-pitched sounds like they once did in their youth. 

Sources: (Grunge) (Mental Floss) 

See also: Things that are damaging your hearing, and how to protect it

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