Final answer:
The signal-to-noise ratio is the mathematical ratio between the power of a primary signal and the power of background noise present simultaneously. For barely discernible differences in sound intensity of the same frequency, this ratio corresponds to a 1 decibel difference.
Step-by-step explanation:
The question refers to the signal-to-noise ratio (SNR), which is a measure used in science and engineering to quantify how much a signal has been corrupted by noise. The SNR is the mathematical ratio between the power of the primary signal and the power of the background noise that is present at the same time. For example, when dealing with sounds of identical frequency, if the first sound is just barely discernible as louder than the second, then the first sound is at the threshold of the just noticeable difference in sound intensity, which is related to the concept of the minimum audibility curve in psychoacoustics. In general, this ratio can vary depending on the threshold of human hearing, but a standard reference value is often taken as a ratio of 1:1.26 in power, which corresponds to a difference of around 1 decibel (dB).