Sounds humans can't hear

Elephant rumbles:
 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. 

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. 

Bat echolocation:
Bats do this by using squeaks and clicks up to 160 times per second, which range in frequency from 20 to 200 kilohertz. 

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

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

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.

Acoustic weapons:
Acoustic weapons may emit audible and inaudible sounds that humans can't even hear.

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