How Do Noise-Canceling Earphones Work?

Origins

Noise-canceling headphones let people listen to their favorite music without the intrusion of ambient noise. Noise from the surrounding environment is the bane of anyone who wants to listen to music. Noise-canceling headphones are vitally important for anyone who likes to listen to music in total surrounding silence. Noise-canceling headphones are an invention of the Bose company, and are more than two decades old. Advancements in electronic chip technology have allowed headphones to eliminate all but the most persistent external noise.

The Technology

The most effective noise-canceling headphones come in circumaural style, which means the headphones sit around the ear, instead of directly on it. That allows an airtight seal to be established. That seal eliminates much of the ambient noise. Noise-canceling headphones come in two styles, passive and active. Passive noise-canceling headphones work primarily by using materials that absorb high-frequency sound waves. The headphones are typically stuffed with thick layers of sound-absorbing materials. Active noise-canceling headphones work on a different principle. The remaining noise is handled by the headphones' onboard computer chips, which work on the theory that noise can be eliminated or minimized by producing a sound that is 180 degrees out of phase with the incoming sound wave. For example, a sound wave looks much the same way as a wave on a river or ocean. The peaks and valleys inherent in the wave control the actual sound of the wave. As the sound waves of ambient noise enter the external headphone speaker, they are analyzed by an onboard computer chip contained within both headphone cups. The computer chips contained within the headphones then cause the headphone speaker to create a sound that is directly opposite than the incoming wave. This is known as destructive interference, and the destructive influence effectively blocks the low-frequency sound waves that threaten to interfere with a user's listening experience. The sound-dampening insulation contained within the headphone reduces the high-frequency noise, thus creating a much more effective noise-canceling effect. Of course, these active systems do require power, which in the original headsets was obtained through power cords. Newer model headsets, however, use rechargeable batteries and a charging cradle.

Health Benefits

Noise-canceling technology was a major leap forward for users who work in noisy office environments or travel frequently on planes or trains. The noise-canceling technology can help alleviate travel fatigue and jet lag, which many health experts theorize is caused by constant, low-frequency noise infiltration. Noise-canceling headphones are being prescribed by some physicians for patients who are frequent travelers.

References

• Bose