2S5: Acoustic vibration monitoring

Tom Murphy, Corporate Training Manager, SDT Ultrasound Solutions


Ultrasound is gaining increasing acceptance in the world of rotating machinery condition monitoring either because of its capability, versatility, simplicity or a combination of all three. There is no doubt that considering ultrasound as the advancement of the screwdriver in the ear appeals to many engineer and technician alike.

In this presentation the operation of a modern-day ultrasound system is explained along with how that instrument can record a signal which can be used for analysis and diagnostics.

Ultrasound detects friction, impacting and turbulence. These three characteristics exhibit themselves in many of the traditional defects we try to locate using vibration analysis. Ultrasound is therefore an ideal assistant in that process of detection and identification.

There are two operating modes for ultrasound: airborne and structure borne. Airborne ultrasound is frequently labelled as the tool for air leaks, steam leaks and electrical inspections. However, ultrasound has many applications in the rotating machinery world in this airborne mode. In this presentation you will hear mechanical looseness, coupling misalignment and defective bearings all of which have been identified using airborne ultrasound.

Contact ultrasound appears on many vibration wallcharts as one of the ways to detect Stage 1 bearing failures – and rightly so. Friction and high frequency intermittent clicks and pops are the key characteristics of these early failures which are easily detected using ultrasound. In this presentation you will hear bearing defects and see how those defects can be diagnosed using standard vibration analysis methods.


Degree in Acoustics Chartered Engineer Certified Reliability Leader 33 years in vibration measurement, 22 years using IR and 16 years using ultrasound. Tom Murphy has worked in the field of vibration measurement and specifically condition monitoring for most of his professional life. He now assists Companies to develop or re-vitalise their programs with a clear focus on the overlap between the various technologies.