I agree with the distinction between flow induced vibration and acoustic vibration. We (I believe mistakenly) use the word acoustic in our dynamics course notes in itemizing different types of harmonic loads in piping systems.
CAESAR II is a beam bending program. We are calculating monents and stresses resulting from deflection off the centerline. Acoustic vibration produces high frequency response that cannot develop the deflections we expect (a tremendoous amount of energy would be required). Instead, as pointed out, acoustic response would be found in shell wall vibration. It's important, but not the realm of CAESAR II.