The loudness level of a sound, D, in decibels, is given by the formula
$$
D=10 \log \left(10^{12} I\right)
$$
where I is the intensity of the sound, in watts per meter2. Decibel levels range from 0, a barely audible sound, to 160, a sound resulting in a ruptured eardrum. (Any exposure to sounds of 130 decibels or higher puts a person at immediate risk for hearing damage.) Use the formula to solve Exercises 117–118.
What is the decibel level of a normal conversation, $3.2 \times 10^{-6}$ watt per meter $^{2} ?$