What is destructive interference?

Destructive interference occurs when two waves meet in such a way that their crest aligns with the trough of another wave, effectively cancelling each other out. This results in a reduction of amplitude. In practical terms, if the two waves have the same frequency and are perfectly out of phase, the combined amplitude can be significantly lowered or even completely nullified, resulting in silence or minimal output in some cases.

This phenomenon illustrates how wave interactions can lead to altered sound levels, as seen in scenarios like noise-cancelling headphones. When sound waves from the environment are met with waves produced by the headphones that are out of phase with the incoming sound, the resulting interference can cancel out the noise. Hence, the answer accurately reflects the nature of destructive interference in wave behavior.