And now that We are so deep into sound... 
Here´re some fun facts about it

-white cats with blue eyes are usually deaf
-wind doesn´t make a sound until it blows against an object

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  -there is no sound in space
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  -sound travels 4.3 times faster through water than in air
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•  -dolphins can hear underwater sounds from 24km (15miles) away
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  -most cows produce more milk when they listen to music.
• -elephants communicate in sound waves below the frequency that humans can hear
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  -sound travels 15 times faster through steel than air
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  -a cat can keep purring while inhaling and exhaling
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  -a whip makes a cracking sound because its tip moves faster than the speed of sound
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  -when baby polar bear cubs are born they cannot see or hear for their first month
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  -akousticophobia is the fear of noises
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  -lion's can't roar until the age of 2
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How to calculate the depth of ocean?

When we want to know the depth of ocean, we need to use sound equipment.
the name of this equipment is Sonar.
The principle is simple. Sonar makes the sound to ocean. Then sound travels the ocean until the bottom. After touching the bottom, the sound come back to mechine. Now we have to calcuate. Calculating the velocity of sound times the seconds to come back, we can get the distance from the ship to the bottom
In this way, we can find the group of fishes when we are fishing with ship.

Are you aware of all the applications of sound? Here is a video of some of the coolest ones: