Visualization of vibration and sound using scanning and holographic methods

Two scanning techniques are now being used to determine the vibrational patterns and far‐field sound radiation of complex vibratory systems. One technique is a near‐field scanning apparatus which scans the vibrator and gives a three‐dimensional display on graph paper of the nodal patterns. The other scanning technique uses the principles of holography to locate far‐field sound sources on the vibrator. These two methods, coupled together, have demonstrated a unique capability to locate acoustic sources and hot spots on vibratory systems.