Nomenclature a, b = integers arg min = the argument of the minimum B = blade number C 0 = speed of sound, m∕s C M = a constant E = approximation error f = a test function g = approximation of f g min = arg min kĝk 1 J = Bessel function of the first kind k = wave number K = compressive sample number M = number of nonzero entries M j = Mach number m = circumferential mode N = dimension of a signal n = integer p = pressure, Pa r = radial axis u, v, w = velocity, m∕s V = vane number x = axial axis θ = circumferential angle, rad θ K = circumferential position of Kth microphone, rad ρ = density, kg∕m 3 ω = angular frequency, rad∕s Subscripts 0 = stationary value m = variables related to the mth mode Superscriptŝ = Fourier transform 0 = disturbance