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Noise cancellation, also known as noise reduction, is a method for reducing unwanted sound. There are generally two methods of noise cancellation, passive noise cancellation (PNC) and active noise cancellation (ANC).PNC utilizes sound absorbent to absorb noise or sound-proof materials to block noise. ANC reduces unwanted sound by the addition of a second sound specifically designed to cancel the first.
ANC comprises an electronic sound device, which generates inverted wave (anti-noise) of the amplitude identical with that of unwanted sound (noise). The anti-noise acoustically merge with the noise and offsets the noise as a result.Figure 1 depicts the waveform of the residual noise after the superposition of the primary noise and the anti-noise. ANC system is as effective as the accuracy in generating the amplitude identical with that of the noise.
TECHNOLOGY TREND : ANC IN AUTOMOBILES ANC is not exclusive to earphones and headphones any longer, and is being applied to new models such as Impala and QM6. While ANC is effective in limited space associated with earphones and headphones, it is difficult to block noise from the ground or wind from larger spaces like vehicle interiors. However, ANC is applicable against the steady noise from engines and has been applied to new vehicle models. We predict ANC technology will improve and become commercialized further.
| ANC SPEAKER SPECIFICATION | |
|---|---|
| SPECIFICATION | FULL RANGE SPEAKER TYPE : Speakers that cover all frequency range are required. However, their roll in mid-range frequencies is especially important as cancelling audible noise to human ears is the priority.
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| SIZE | 2 inches or smaller : ANC is more effective with the devices covering wider spaces. Therefore, the smaller the better. |
| F0 | 130 Hz ±30% |
| SPL | 80 dB ±5 |
