Peter Barclay of the Gatwick Area Conservation Group said a second runway would mean significant extra noise for 20, 000 people.

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This should lead to a significant reduction of noise, air pollution and congestion.

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"It's been more noise than significant money, " said Collin Lau, former head of real estate at the giant state-run China Investment Corp.

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It was found background noise had a "significant effect" on stress levels.

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But unless you are very careful and disciplined, it is perilously easy for the noise to overwhelm the signal and for the tumult of your inbox to exact a significant cognitive overhead on your daily productivity.

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Chrysler has also put a significant amount of unit-cost into soundproofing, with acoustic windshield and front-window glass and other noise abatements.

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