How Do Noise Canceling Headphones Work?by Dwight Valdez
There are two types of headphones designed to reduce the interference of background noise. Passive noise canceling headphones muffle external sound to lessen the interference with music or recorded speech. Active noise canceling headphones electronically decrease external sound to produce a quiet listening environment.
Passive noise cancellation
Passive noise canceling utilizes the natural muffling characteristics provided by circum-aural headphones. This design is shaped like a cup with the rim surrounding your ear. The rim is made of high-density foam and sound dampening material. It is soft and creates an acoustic seal that blocks up to 20 decibels of noise.
Active noise cancellation
Active noise canceling headphones can produce 20 decibels more noise reduction than passive noise canceling headphones. It takes advantage of the circum-aural sound dampening design of passive noise cancellation and uses phase canceling technology.
Phase cancelling technology
Phase canceling technology is the key feature of active noise canceling headphones. It uses a microphone inside the headphone to pick up the external noise that the circum-aural cushions are unable to block out. The phase canceling circuit analyzes the frequency (pitch) and intensity (loudness) of the noise. Then the circuit generates a mirror image of the noise that is 180 degrees out-of-phase. The headphone speaker plays the "anti-noise" along with your music or recorded speech. The artificially generated "anti-noise" is the exact opposite of the external noise that made it past cushions. So when the two noises meet, they cancel each other out. The net effect is that the volume of the external noise drops dramatically, and the audio you are listening to becomes easier to hear.
Noise canceling headphones are ideal for places and activities where there is a lot of background noise. The sound isolation from ambient noise reduces fatigue on long trips. Active noise canceling headphones require a power source so you will use a battery, which usually is incorporated into the left or right earphone. Passive and active noise canceling headphones are larger and heavier than ear buds or earphones. However, they can be more comfortable when worn for long periods of time because they have soft cushions that don't press into or on the ears.
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