Wave Interaction, Beats, Destructive Interference

When waves come into contact with each other they can interact together to increase or decrease amplitude.

If two sound waves are slightly off in frequency you can hear the peaks where the waves add together (constructive interference), called “beats.”

If two identical waves are off by a phase angle of pi then there will be complete destructive interference, meaning that all the energy will be cancelled while they are in contact.

Sound cancelling headphones take advantage of this property by creating waves that cancel background noise.