Which unit is used as a logarithmic ratio to measure changes in sound intensity or electric signals?

The correct answer is the decibel (dB), which is indeed utilized as a logarithmic ratio for measuring changes in sound intensity or electric signals. The decibel is a unit that expresses the ratio of two values, typically power or intensity, on a logarithmic scale. This logarithmic nature allows the decibel to conveniently condense the vast range of sound pressures or electrical signal levels into a more manageable format.

In audio applications, a change of 10 dB represents a tenfold increase or decrease in the power of the sound, while a change of 20 dB corresponds to a tenfold increase or decrease in sound intensity. This scaling is essential in both audio and telecommunications, as human perception of sound is generally logarithmic rather than linear—meaning that people perceive sound intensity changes in a way that aligns more closely with logarithmic values.

Other units such as lux are used for measuring illumination, hertz measures frequency, and ohm measures electrical resistance. These units serve different purposes and do not function as a logarithmic ratio for sound intensity or electric signals.