* Why? What? How? 🤔 * * Question: * Will there be resound in the hills? * Answer: * Sound waves travel in the air at a speed of about 332 meters per second. If we burn loudly in front of the hills, we will hear the same screams after a few seconds. This is called echo. Sound travels in the form of waves. Sound waves propagate in all directions from the vocal cords. Some of those sound waves are reflected when any of these are obstructed. So we hear the sound waves coming back and forth. In fact we can not hear it all, even if every noise hits an obstacle and comes back. Can't hear the echoes coming back within a tenth of a second. This means that in order for the echo to be heard we must return the sound waves that left us with a duration of more than 1/10 second. When calculated in that way the barrier that reflects the sound waves turns out to be at least 17 meters away from us. There should not b...