SHORT-TIME COHERENCE FUNCTIONS: INSTANTANEOUS AND TUNED

✍ Scribed by D.J. McCarthy

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 348 KB
• Volume: 11
• Category: Article
• ISSN: 0888-3270
• DOI: 10.1006/mssp.1996.0073

✦ Synopsis

The ordinary coherence function is a convenient tool for determining the extent to which two signals are linearly related and, if used carefully, can be used to help identify and rank the major sources of vibration in a structure (or sound in a room). In developing a vibration-based diagnostic methodology for reciprocating machinery, there is a need for such a tool to identify transient sources of vibration. A method is also required to emphasise the coherent vibration for diagnostic signature recovery, a process by which impulsive source waveforms are recovered from transient vibration signals measured non-intrusively on the casing of a machine. To satisfy these needs, the ordinary coherence function was extended to a time-dependent format called the short-time coherence function. The instantaneous form of the short-time coherence is useful for initial source identification efforts. The tuned form of the short-time coherence is useful for examining likely sources in more detail, and provides a means for separating the coherent and incoherent vibration signals for use in the signature recovery process.