Wave Interference

Wave Interference
Wave interference occurs when two or more sound waves from different sources present at the same time. At the point where they meet each other, interaction occurs and a new wave will be produced. When they have passed each other, they change back to their original pattern (in ideal condition, which no energy loss).
How to predict the shape and pattern of the new wave? It is actually easy to find the new wave formed since the new wave is the sum of all the different waves. There are two types of wave interference: constructive interference and destructive interference. Constructive interference occurs when all waves are at the same level. And destructive interference happens when waves meet at different level. In a constructive interference, the waves strengthen each other and create a wave with a higher intensity.

In the diagram (above) when waves meet at different levels at the same time, their interaction creates a wave with a dampened or lower intensity and it is destructive interference.

What happens when interference happen? What's the actual result of it that we can observe or hear?
When constructive interference happens, the waves add up and create a new wave  with higher amplitude. This higher amplitude also means a louder sound . Sometimes our ears cannot hear the sound, but a louder sound is created indeed

When destructive interference happens, the waves add up together as well but involve positive and negative numbers if we assume the top half portion is positive and the bottom half portion is negative. Then the new wave formed is smaller and have a lower amplitude than before When waves are interfering with each other destructively, the sound is louder in some places and softer in others. As a result, we hear pulses or beats in the sound.