What is Resonance Explained in Simple Terms

Resonance of sound waves is an effect which makes all the beautiful sounds around us possible. If you love the sound of pipe organ, you should give thanks to resonance.

Resonance of sound waves is an effect which makes all the beautiful sounds around us possible. If you love the sound of pipe organ, you should give thanks to resonance.

What Is Resonance: Sound is a wave as I explained in my Factoid What Is Sound: Explain The Physics To A Layman!. This wave can be visualized as shown in the picture on the left. The wave in this picture has a middle point and two maxima points, one on top and one on bottom. For the sake of easy identification these points can be called maxima (the one at the top) and minima (the one at the bottom).

By any reason, if the wave were to be reflected back either at a middle point, or at one of the maxima, the original and reflected waves would fall just opposite to each other. There will be a minima opposite a maxima, and vice versa. The result is called a resonance or a standing wave. Interestingly, whenever a resonance is produced, the audible sound feels louder and even sweeter. This is the principle used in all wind-blown musical instruments, more so in those instruments that use pipes to create resonance.

In the picture on the left you can see the resonant wave or standing wave of four different frequencies when they are reflected at the middle (mean) position. The reflected wave stands exactly opposite in the maxima-minima arrangement of the waves. Such reflection from the "mean" or middle position can take place only when one end of the tube is closed.

A similar resonance effect is produced when reflection takes place at either the maxima or the minima of the wave. Such reflection can take place both in a closed as well as in an open tube. The picture on the left shows the reflection of waves of three different wavelengths at the maxima/minima points in an open tube. The same would happen if the tube were closed at the ends.

The two effects mentioned above, reflection at the middle position or at the maximum/minimum positions of a wave produce a special effect, and this effect is called "resonance". The resonant wave is always louder than the original wave, and often it is also sweeter.

Uses Of Resonance: You must have noticed that almost all wind-driven instruments have a hollow space inside them. This hollow space or cavity provides the area where sound can resonate. Once it resonates, the resonance coupled with many other factors creates the sweet musical sound of the instrument that you and I enjoy. The hollow space is called a resonant cavity.

When you whistle, your tongue and mouth create a resonant cavity. When a policeman or a coach blows a whistle, it is the cavity in the whistle that produces the loud sound via resonance. The wind-driven sirens of yesteryears also use the same effect. In fact the use of resonance is so common in human life that it would be dull if resonance did not exist.

Note: If you found this Factoid useful, then you need to see the rest of my factoidz at Shastri

Pictures: Wiki Commons

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