![Diagram of four waves with different frequencies.](http://static.sciencelearn.org.nz/images/images/000/004/105/full/PHYSICS_SOUND_ART_04_Sound_wave_interference_Sine_wave_interference_Wave_addition_v3.jpg?1674173139)
Two identical sound waves can add constructively or destructively to give different results (diagrams A and B). Diagram C shows addition of waves with different frequencies. Diagram D shows addition of waves with nearly the same frequency, which forms beats.