APFIVE Decibel Reduction from a Noise Barrier
Suppose traffic noise from a highway is measured at 70 decibels (dB). If a newly installed noise barrier is claimed to reduce the sound level by 40 percent, all of the following statements are true EXCEPT:
A
A 40% reduction lowers the noise level from 70 dB to $$70 \times (1 - 0.4) = 42$$ dB.
B
The noise level remains unchanged at 70 dB after the installation of the noise barrier.
C
Noise barriers are effective devices for decreasing ambient sound levels in urban settings.
D
Percentage reduction calculations imply a proportional drop in the noise level in this context.
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