Sound level L in units of decibel (d_B) is determined by L = 20 log10(p/p₀) where p is the sound pressure of the sound (in Pascals, abbreviated P_a), and p₀ is a reference sound pressure equal to 20 × 10^–6 P_a (where L is 0 d_B). The following table gives descriptions for certain sound levels. Threshold of pain 130 d_B Possible hearing damage 120 d_B Jack hammer at 1 m 100 d_B Traffic on a busy roadway at 10 m 90 d_B Normal conversation 60 d_B Calm library 30 d_B Light leaf rustling 0 d_B Write a program that reads a value and a unit, either d_B or P_a, and then prints the closest description from the list above.