The Nyquist frequency is equal to one-half the sampling rate. Shannon’s sampling theorem states that a sampled time signal must not contain components at frequencies above the Nyquist frequency. Otherwise, an aliasing error will occur. * * * Here are some papers: Notes on sample… Read more
A new helicopter design must undergo thorough testing to ensure the reliability of the design with respect to vibration. A new design undergoing testing may encounter severe vibration while it is on the ground, preparing for takeoff. A similar problem may occur immediately after landing. Many helicopters… Read more
Bessel Function Table: Bessel_functions.pdf * * * Tutorials Referencing Bessel Functions Newton-Raphson Method Applied to Vibration Problems: Newrap.pdf Longitudinal Vibration of a Tapered Rod: taper_long.pdf Natural Frequencies of Circular Plate Bending Modes: circular.pdf An Introduction to Slosh: slosh_intro.pdf – Tom Irvine
Ideal random vibration has a normal distribution histogram. (In contrast, measured random vibration in the field may be nonstationary and thus vary from this ideal. ) Here are some resources: An Introduction to Random Vibration Integration of the Normal Distribution Paper Here is a software… Read more
Here are some useful references: Laplace Transform Table Partial Fractions Bessel Functions * * * Examples of the Laplace Transform as a Solution for Mechanical Shock and Vibration Problems: Free Vibration of a Single-Degree-of-Freedom System: free.pdf Response of a Single-degree-of-freedom System Subjected to a Unit… Read more
The mean filter is a simple sliding-window filter that replaces the center value in the window with the average (mean) of all the values in the window. The mean filter is intended as a lowpass filter which smooths the data. It may also be used… Read more
The scripts in integrate_th.zip integrate an acceleration time history to a velocity time history and/or a velocity time history to a displacement time history. The main script is: integrate_th.m The remaining scripts are supporting functions. Integrating acceleration to velocity typically causes a spurious offset in… Read more
(Image courtesy of A. Bhatia) Hotels have central heating, ventilation and air conditioning (HVAC) systems which generate noise that may disturb guests’ sleep. The noise propagates through ducts and room surfaces. Individual room air conditioning units may also cause unpleasant noise. The transmission paths in… Read more
These Matlab scripts calculate the steady-state response of a single-degree-of-freedom (SDOF) system to a sinusoidal force or base excitation: steady.zip – Tom Irvine
I recently flew from Spokane to Seattle, Washington on an Alaska/Horizon Air Bombardier Q400 aircraft, similar to the one in the above image. This model aircraft has two Pratt & Whitney Canada PW150A turboprop engines. I captured the following video during cruise using a Motorola/Android… Read more