Chapter 1: Where Do Sound and Noise Come From? — From Microscopic Vibrations to Airborne Acoustic Radiation
A comprehensive physical acoustics and mechanical engineering guide on how sound and noise originate: longitudinal air compression waves, four microscopic excitation mechanisms of mechanical noise (impact shock, time-varying mesh stiffness TVMS, stick-slip friction, aerodynamic turbulence), transmission paths (structure-borne vs. airborne), gearbox casing soundboard amplification and coincidence effect, and decibel (dB) vs. Pascal (Pa) physics.
Chapter 2: What Sounds Is the Human Ear Most Sensitive To? — Equal-Loudness Contours & Psychoacoustics Demystified
A deep dive from auditory physiology and mechanical engineering perspectives into the non-linear acoustic filtering of human hearing: why the external ear canal's quarter-wavelength resonance amplifies 2.5k–4kHz by +15dB, how middle ear ossicles achieve impedance matching, why bass is inaudible at low volumes and overwhelming at high volumes (ISO 226), why dB(A) sound level meters fail in gear whine diagnosis, and the four core psychoacoustic metrics: Loudness (Sone), Sharpness (Acum), Roughness (Asper), and Prominence Ratio (PR).
Gearbox NVH & Mechanical Noise Diagnostic Handbook
A practical, easy-to-understand engineering handbook on gearbox noise and vibration testing. Covering sound pressure and decibels (dB/dBA), why human ear listening is unreliable, the difference between gear whine and rattle, sensor setups, and transitioning to digital FFT diagnostics.
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