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.