magnitude the property of relative size or extent (whether large or small); "they tried to predict the magnitude of the explosion"; "about the magnitude of a small pea"
signal level the amplitude level of the desired signal
amplitude -
The maximum absolute value of some quantity that varies.
Wikipedia
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation. If a variable undergoes regular oscillations, and a graph of the system is drawn with the oscillating variable as the vertical axis and time as the horizontal axis, the amplitude is visually represented by the vertical distance between the extrema of the curve.