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The threshold of hearing is 10-12 watts/m2 or 0 dB. How many times more intense than the threshold of hearing is 70dB and what is the actual intensity (in watts/m2) at the 70 dB level? Show the physics.
Solution:
The threshold of hearing is assigned a sound level of 0 decibels (abbreviated 0 dB); this sound corresponds to an intensity of 1*10-12 W/m2.
A sound that is 10 times more intense ( 1*10-11 W/m2) is assigned a sound level of 10 dB. A sound that is 10*10 or 100 times more intense (1*10-10 W/m2) is assigned a sound level of 20 db. A sound that is 10*10*10 or 1000 times more intense (1*10-9 W/m2) is assigned a sound level of 30 db. A sound that is 10*10*10*10 or 10000 times more intense (1*10-8 W/m2) is assigned a sound level of 40 db.
Hence a sound that is 10 ^ 7 (10 to the power of 7) or 10000000 times more intense (1*10-5 W/m2) is assigned a sound level of 70 db.
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