Why did I hear echoes when I shouted on the top of the mountain, but in the room?

Why can echoes be heard in the mountains and not in the room?

According to ScienceABC, in a popular story of the Greeks, Zeus often left Mount Olympus to visit Earth and tease beautiful people on earth. In the end, Hera, Zeus' wife, was also suspicious and decided to go back to her amusing husband.

On the way, Echo - a beautiful goddess in the forest - accompanied Hera. With his nature or "talkative" , Echo constantly follows and talks, telling the goddess. Of course, Hera couldn't find Zeus because of this harassment. Too angry, the goddess Hera cursed Echo, making Echo only repeat what she heard. Since then, the phenomenon of repeating sounds - or echoes - is called Echo .

That echo sound is called echo.

When you stand on a hill or in the middle of a large forest and shout your name, after a while you will hear the sound of your name repeating again (though it breaks down and gets smaller). That echo sound is called echo.

The echo returned to the source emitting it like a boomerang. In order to return to the direction of the source, sound or light waves must travel through space in an oval or more orbital way or reflecting from a certain surface. Another type of echo is the reflection of sound waves from objects in the vicinity of the source.

However, if the echo is merely a reflection of sound , why don't we listen to them in small rooms, where there are more surfaces to reflect on? The answer lies in how the human brain perceives sound.

How does echo happen?

For a well-reflected sound, the sound must have a loud enough intensity and return with a certain delay. This delay is directly proportional to the distance between the reflected surface from the sound source and the listener.

Our hearing aids are ears pair attached to both sides of the head. When the sound is heard, the human ear cannot distinguish the perceived sound from the original if the delay is less than one tenth of a second.

Sound velocity in dry air is about 343m / s at 25 ° C. Therefore, the reflector must be 17.2 meters longer than the sound source for echoes to be seen in the sound source. When a sound echoes for two seconds, the reflector is 343m away.

In nature, canyon walls or water-facing cliffs are the most common natural settings for echoes. The power of echoes is usually measured in dB of sound pressure (SPL) compared to the direct wave.

Echo is the single reverberation of a sound source. The time between the sound emission and the echo is due to the "distance" that the sound wave must pass until it encounters an obstacle and turns back.

Therefore, the reason the echo is not heard in the room is the reflection sound received in less than 0.1 second or reflective surface at a distance of less than 17 meters.

Another reason you can't hear echoes in the room is wood and sound absorbing mattresses, not reflecting it.