Variable-Speed Testing

Chapter 2.2: How to Diagnose Gearbox Noise Under Variable Speeds? — From STFT Spectrograms to Order Maps & Campbell Diagrams

An intuitive, plain-language engineering guide to diagnosing mechanical noise under variable-speed sweeps (run-up/coast-down) and reciprocating strokes: why a single global FFT goes blind under changing speeds, how to choose the STFT sliding window length, how to read diagonal order rays, horizontal modal bands, and vertical impact stripes, and how to pinpoint critical resonance speeds using Order Maps, Campbell Diagrams, and Order Slices.