How do noise cancelling headphones/earphones work?

No ise - c anc elling head phones / ear phones work by using active or passive noise - c anc elling technology to reduce the amount of external noise that reaches the user ' s ears . Active noise - c anc elling head phones use micro phones to pick up external noise and then generate an in verted sound wave that can c els out the noise . Pass ive noise - c anc elling head phones use materials like foam or memory foam to absorb sound waves and reduce noise . Some head phones also use a combination of both active and passive noise - c anc elling technology . Overall , noise - c anc elling head phones / ear phones can help users focus on their work or music without being distract ed by external noise . </s>