The loudness level of a sound can be expressed by comparing the sound's intensity to the intensity of a sound barely audible to the human ear. The formula D = 10 ( log l- log lo ) describes the loudness level of a sound, D, in decibels, where I is the intensity of the sound, in watts per meter , and lo is the intensity of a sound barely audible to the human ear. Use this information to answer parts (a) and (b) below. . . . a. Express the formula so that the expression in parentheses is written as a single logarithm. Choose your answer below. O A. 10 O B. D = 10 log (1 -10) D = log O C. D = 10log OD. D = 10 log (1 . 10) b. Use the form of the formula from part (a) to answer this question. If a sound has an intensity 1/10th of the intensity of a louder sound, how much smaller on the decibel scale is the loudness level of the less intense sound? decibels softer