How do echoes take place?

An echo happens when a sound is reflected back to the listener after it hits a surface. When you shout nice and loud, your voice travels as sound waves. These waves move outward until they hit a large, hard surface. The surface bounces off the sound and it returns to your ears. Think of it like a ball bouncing back from against the wall. You throw the ball towards the wall and it bounces back.

Not an everywhere instance

Of course, not all places are built for echoes. There are some factors that need to be taken into consideration for that echo factor.

The reflecting surface needs to be far enough for the returning sound to be heard separately, usually 17.2 metres or more. If it is any closer, the reflected sound mixes with the original sound. This mix of the echo with the original sound is what we call reverberation.

Echoes occur best with hard, smooth and large surfaces are required for that reflection. Rock, cement, marble, and glass are common materials which can facilitate an echo. Soft materials like carpets, curtains, and grass absorb the sound waves rather than reflecting it. That’s why they are often used in soundproofing rooms during studio recordings, and why auditoriums and halls are often decked with carpets and curtains.

So, where are echoes commonly heard? They are common in areas such as a mountain, large, abandoned buildings, canyons, and cliffs.

The Gol Gumbaz is the tomb of Mohammed Adil Shah (r. 1627-1656) in Bijapur (now Vijayapura). It is a spectacular and majestic monument set in a serene garden. The hemispherical dome is one of the largest free-standing domes in the world. It is also very echo prone.
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SPECIAL ARRANGEMENT

A formula

As we all know, sound travels at a very high speed, at 343 metres per second in air that is at 20℃. The distance between the reflecting surface and the source of sound is calculated with this very formula,

D = V x T / 2

Where:

• D = is the distance to the surface.

• V = is the speed of sound

• T = is the total time elapsed from the original sound to the heard echo.

Echo-tech

While echoes may not be needed in studio recordings, they do come handy elsewhere. Echoes are used for navigating and detection, like in SONAR; which measures ocean depth and finds objects underwater, in ultrasound; and in industrial testing, to find internal cracks, voids or flaws. Animals like bats and dolphins use it to navigate themselves in dark environments.

Echoes are a fascinating example of how sound behaves in the environment. From mountain valleys to advanced technology, they reveal the remarkable journey that sound waves take through the world around us.