Either it is a sound wave, light wave or any other wave depending on the way in which 2 waves superpose with each other is known as interference. Interference gives rise to a resultant wave of lower, greater, or the same amplitude.
According to the principle of superposition of waves, when two or more waves traveling with same amplitude and frequency meet on the same point, the outcome resultant wave formed will have an amplitude equal to the individual amplitudes of the waves.
Two types of wave interference are:
- Constructive interference
- Destructive interference
In constructive interference, crest (peak) of a wave meets the peak of another wave of the same frequency at the same point, then the amplitude of the resultant way is the sum of the individual amplitudes of 2 waves which superposed.
In destructive interference, the crest (peak) of one wave meets a trough (dip) of another wave, then the amplitude of the resultant wave is equivalent to the variation in the individual amplitudes of 2 waves which superposed.
The constructive interference and destructive interferenceare explained briefly in the figure below.
In the Constructive interference, the phase difference between the individual waves is an even multiple of π (180°), whereas in the destructive interferencethe difference between the waves is an odd multiple of π.
the summed variation has a less amplitude than the component variations in the headphones with the noise-canceling ability and is an example of destructive interference.
In a loudspeaker, the summed variation will have a bigger amplitude than any of the components individually and is an example of constructive interference.
The architecture of the building depends on the acoustics. Acoustics decides whether the building is ready to cancel the sound waves or sum up the sound in the surroundings. Sound is more pleasing if it is evenly dispersed with no prominent echoes, dead spots or live spots in the auditorium. Acoustics which results in silence or substantially reduced volume creates the dead spots in the building/auditorium. The cause of this effect is due to destructive interference.
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