If decibels report relative changes, what does a positive value indicate about the compared levels?

If decibels report relative changes, what does a positive value indicate about the compared levels?

• A. The actual level is higher than the reference
• B. The actual level is lower than the reference
• C. They are equal
• D. The measurement is invalid

Answer: (A)

Decibels express a ratio between two quantities, not an absolute value. The sign tells you which side is larger. A positive decibel value means the measured level is higher than the reference level. For example, if you’re comparing power, and the actual power is twice the reference power, the value is 10 log10(2) ≈ +3.01 dB, clearly indicating an increase. If the measured level were lower than the reference, the decibel value would be negative, and if they’re the same, it would be zero. The exact number depends on whether you’re using power or amplitude, but the positive sign always denotes a higher level compared with the reference.

Decibels express a ratio between two quantities, not an absolute value. The sign tells you which side is larger. A positive decibel value means the measured level is higher than the reference level. For example, if you’re comparing power, and the actual power is twice the reference power, the value is 10 log10(2) ≈ +3.01 dB, clearly indicating an increase. If the measured level were lower than the reference, the decibel value would be negative, and if they’re the same, it would be zero. The exact number depends on whether you’re using power or amplitude, but the positive sign always denotes a higher level compared with the reference.