Sound Intensity The decibel level of a TV set decreases with the distance...

Sound Intensity The decibel level of a TV set decreases with the distance from the set according to the formula

where D is the decibel level and r is the distance from the TV set in feet.

a. Find the decibel level (to the nearest decibel) at distances of 10, 20, and 50 feet.

b. Express D in the form D = A + B log r for suitable constants A and B. (Round A and D to two significant digits.)

c. How far must a listener be from a TV so that the decibel level drops to 0? (Round the answer to two significant digits.)