Acoustic Techniques for Machinery Diagnostics
R. Bruce Tatge · The Journal of the Acoustical Society of America · 1968
Reliability of machinery is improved by maintenance procedures that detect malfunctions at an early date so that corrective action can be taken before failure occurs. When deterioration is recognized, spare parts can be ordered as needed and repairs scheduled for a noncritical time. Use of sound or vibration as the carrier of diagnostic information has several advantages over other techniques. First, many malfunctions are first evidenced by changes in the sound or vibration signal. Second, sensor attachment can be accomplished with minimum modification of the machine. Third, such diagnosis does not require disassembly of the device under study. Evaluations of this kind by skilled mechanics have been used for years, but the full potential can only be realized by application of modern techniques of problem definition and acoustic signature evaluation. Understanding of the processes by which signals are generated and transmitted permits the investigator to develop an analytical model by which normal and abnormal signatures can be established. Once the discriminants are known, it is possible to choose and locate sensors and decide on a data-analysis technique for extracting the desired information from the raw signal. In some instances, this may be found most easily by spectrum analysis, while on others the waveform contains more meaningful information. New tools, which have been useful for signal analysis, are transient averaging, high-speed spectrum analysis, and recognition of signal patterns by digital techniques.