Positive decibels report signals that are ______ in strength or getting ______.

• A. Decreasing; Smaller
• B. Increasing; Larger
• C. Increasing; Smaller
• D. Decreasing; Larger

Answer: (B)

Positive decibels mean the signal is above the reference level, i.e., the strength has grown. In the decibel scale, a ratio greater than 1 yields a positive value, and as that ratio increases, the dB value increases. For power, dB = 10 log10(P/P0); if P > P0, the result is positive and grows with P. For voltage or current (with the same impedance), dB = 20 log10(V/V0); again, a larger V than V0 gives a positive, larger value. So positive decibels report signals that are increasing in strength or getting larger. If the signal weakens, the decibel value would be negative. For example, doubling power is about +3 dB, eightfold is about +9 dB.