F.4 Maths( log )
2010-04-01 4:51 pm
A cassette player is playing at a sound intensity level of 55 dB. If the sound intensity increases by 8 dB, find the % increase of the sound intensity.
回答 (1)
2010-04-01 5:56 pm
✔ 最佳答案
Let A = reference sound intensityB = original sound intensity
C = new sound intensity
so 55 = 10 log B/A = 10 log B - 10 log A ..........(1)
and (55 + 8) = 10 log C/A = 10 log C - 10 log A ...........(2)
(2) - (1) we get
8 = 10 log C - 10 log B
8= 10 log C/B
so C/B = 10^0.8 = 6.3
% increase = (C - B)/B x 100% = 530%.
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