Acoustic signals. structure borne, have long been used to detect the integrity of various machinery. This presentation discusses the state of the art of using the ultrasound (high frequencies beyond the audible range) of machine elements and structures to detect failure or malfunction conditions. The paper will describe a recently developed technique, the High‐Frequency Resonance Technique (HFRT), its principles, and results of applications in detecting rotating machine element failure especially in bearing inspection, as well as its potential for extensive machinery condition monitoring. A brief discussion of the use of fiber optics in the monitoring of vibrations and detection of flaws in rolling element bearing will be presented. This relatively new technique shows promise for fault detection in the areas of inspection and vibration measurement in general. The paper will also discuss the use of high frequency signal detection of pulses generated in structures failing under dynamic loads and the potential of the method for nondestructive testing of various structures in important applications.