When two waves with similar but slightly different frequencies move in the same medium, a distinctive interference pattern emerges.
The combination of the two sililar waves oscillates between large and small amplitudes. When this happens with two sound waves, the process is called beats
Notice that when the two original waves are in phase they combine to create the largest amplitude on the combined wave.
When the original waves are completely out of phase, they mostly cancel each other out.
When two sounds of similar frequency are played the oscillating amplitude of the combined wave is heard as an oscillation in loudness. The sound hear gets louder and quieter over time. The frequency of the beats is equal to the absolute value of the difference of the two original frequencies.
Use the input boxes below to experiment with beats. You will need to turn on your sound. Each time you adjust the frequency you must hit the play button again to activate the new frequency.