Wave interference can be constructive or destructive in nature. Shown here in purple are two oscillators each emitting an identical frequency. When frequency waves meet the effects are multiplied.
Where two crests of a wave meet, they amplify each other and a higher crest is formed, this is known as constructive interference. When a crest meets a trough they neutralise each other and this is referred to as destructive interference.
Interference effects can be observed with all types of waves, including, light, radio, acoustic, surface waves and more.