The microphone is a small device installed in the Quietcomfort 3 headphone. The microphone is to capture noise from the surroundings. It is placed inside the ear cup and it "listens" to the external sound that cannot be blocked passively. Inside the ear cup, noise canceling circuitry electronics also been placed. The electronics sense the output from the microphone. Then, the noise canceling circuitry electronics generated a "fingerprint" of the noise, noting the frequency and the amplitude of the upcoming wave. After that, they created a new wave that is 180 degrees out of phase with the wave associated with the sound. The new wave will be transferred to the speaker.
The speaker in the Quietcomfort 3 headphone is an electronic device that creates another sound with different amplitude. The "anti-sound" created by the noise canceling circuitry is fed into the speaker along with the normal audio. The "anti-sound" created by the noise canceling circuitry erases the noise by destructive interference, however, the destructive interference does not affect the desired sound waves in the normal audio. Thus, the Quietcomfort 3 headphone is able to provide an additional noise reduction of 20 decibels. In addition, the headphone is compact with on-ear design. The Quietcomfort 3 ear cushions established a critical acoustical seal between the headphones and the ears. The ear cushion outside dimensions is measured 2 7/8" H x 2 1/4" W (7.5 cm x 6 cm).
Left: The rechargeable lithium-ion battery; Right: The charger
The battery is an electronic device that gives life to the Quietcomfort 3 headphone. Inside the Quietcomfort 3 headphone, a rechargeable ba ttery is inserted, that is the lithium-ion battery. The rechargeable lithium-ion battery provides approximately 25 hours of reliable run time. The rechargeable lithium-ion battery output power is 3.7 VDC, 200 mAh. The lithium-ion battery may be considered expensive; however, it is more convenient compared than using the average AAA batteries. The rechargeable battery is mainly designed for long hours of travel and thus, it is much comfortable to bring along. The lithium-ion battery charger is small and collapsible prongs for easy storage. The charger is dual rated, with input of 100-240 VAC 0r 50-60 Hz.
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