Measurement of Axial Velocity Profiles and Resulting Acoustical Fields of a Rod

摘要

Sinusoidal stress waves over the frequency range 10-100 KHz were transmitted down a cylindrical aluminum rod twelve feet long and one and one-half inches in diameter. Using a modified Twyman-Green interferometer and a high sensitivity, fast rise time photo-diode radial distributions of axial displacement were measured at the radiating face of the rod while it was under continuous-wave excitation. Measurements verified the almost piston-like displacement profiles for low frequencies and indicated increased distortion of the face with increasing frequency. Nodal cylinders of axial displacement in the rod were found to occur beginning at about 30 KHz with only the lowest symetric mode propagating in the rod. (Author)