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T5B10
Which decibel value most closely represents a power decrease from 12 watts to 3 watts?
Pick an answer to check it.
Answer: C. -6 dB
dB = 10 x log(P2 / P1). Step: 3 W / 12 W = 0.25, and 10 x log(0.25) = about -6.02, so about -6 dB. Another way: 12 to 6 W is half (-3 dB), and 6 to 3 W is half again (-3 dB), for a total of -6 dB.
Tip: Each halving of power = -3 dB.