Root mean square (RMS), often referred to as an average level, is a measurement of the signal variance from zero. The average of a sine wave would always result in zero because the positive and negative values would average to zero. Therefore, an averaging calculation alone would not be meaningful to us. RMS performs squaring so all the values will be positive. Because the values are squared initially, the square root is taken to recover the value. The average is taken from these positive values to give us a meaningful result.
RMS - Defintion
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