Two Step Analysis When you hear "SN ratio", you may think "What is S and N ?". But in quality engineering , there is no answer for this question. The answer is in communication engineering.
In communication engineering,
"S" is signal. And "N" is noise.
SN ratio in other way is written as "S/N ratio".
"SN ratio" = "Voltage of signal" / "Voltage of noise"
If SN ratio of the speaker is high, the noise of the speaker is low. SN ratio is an index to evaluate the effect of noise to signal.
In quality engineering, the SN ratio for preferably target characteristics is the ratio of average and standard deviation. So we feel something about the ratio of signal and noise. But SN ratios for other characteristics are different.
"SN ratio" in quality engineering is not the ratio of signal and noise.
"SN ratio" in quality engineering is a index to evaluate unevenness.
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