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PowerPoint File:

Webinar_24_Seismic_Shock.pptx

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Matlab script: Vibrationdata Signal Analysis Package

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See also:

Smallwood Algorithm

Seismic Peak Ground Acceleration

Vibrationdata Webinars

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- Tom Irvine

Here is a paper showing how fatigue damage can be calculated from a stress response PSD for a plate excited by an acoustic pressure field:  acoustic_fatigue_plate.pdf

The calculation method is given at:
Fatigue Damage for a Stress Response PSD

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See also:

Steady-State Response of a Rectangular Plate Simply-Supported on All Sides to a Uniform Pressure:  ss_plate_uniform_pressure.pdf

Steady-State Vibration Response of a Plate Fixed on All Sides Subjected to a Uniform Pressure: fixed_plate_uniform_pressure.pdf

- Tom Irvine

This Webinar unit shows how to perform spectral analyses on sound files using the Matlab Vibrationdata package.

PowerPoint File:

Webinar_sound_files.ppt   -  Matlab & Python

The sample data file for the CRJ900 aircraft is available at:

CRJ900 Acoustics

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The Matlab & Pythons packages are available at:

Matlab script: Vibrationdata Signal Analysis Package

Python Signal Analysis Package GUI

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See also:

Vibrationdata Webinars

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- Tom Irvine

PowerPoint File:

Webinar_23_Classical_Shock_Pulses.pptx

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Matlab script: Vibrationdata Signal Analysis Package

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See also:

SRS Educational Animation

Laplace Transforms in Shock & Vibration Analysis

Vibrationdata Webinars

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- Tom Irvine

American-Airlines-CRJ-200

Figure 1. Typical Bombardier CRJ-200 Aircraft

 

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Figure 2. General Electric CF34-3B1 Turbofan Engine

 

Figure 3.  Fourier Magnitude with Note Peak Frequencies (Hz)

Figure 3. Fourier Magnitude with Noted Peak Frequencies (Hz)

I recently flew as a passenger in a CRJ-200 (aka CL-65) jet similar to the one shown in Figure 1.

This aircraft has two General Electric CF34-3B1 turbofan engines, as shown in Figure 2.

Here are the rotational speeds for each rotor.

N1 Fan Speed       7300 RPM   (122 Hz)
N2 Core Speed   17710 RPM   (295 Hz)

I made an audio recording from within the aircraft cabin nearing the end of climb-out, after hearing some distinct sine tones against the background random noise. The audio file is: CRJ200.wav

A Fourier transform of the sound file is shown in Figure 3.

A spectral peak occurs at 113 Hz, which is 93% of the N1 Fan speed.

A pair of spectral peaks occur at 277 and 278 Hz.  These are about 93% of the N2 Core speed.  The 1 Hz difference could be due to the N2 rotors of each engine being slightly out-of-sync with one another.

The other peaks remain unidentified.

Again, this recording was made from inside the cabin. So the fuselage walls would have attenuated some of the engine-generated acoustic energy, particularly at higher frequencies.

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See also: Bombardier

- Tom Irvine

 

PowerPoint File:

Unit_22_integration_part_2.ppt

Audio/Visual File:

Integeration_Differentiation_part_2.wmv

YouTube Version

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Data Files:

navmat_spec.psd

two_wheeled_trailer_vertical.txt

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Matlab script: Vibrationdata Signal Analysis Package

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See also:

Vibrationdata Webinars

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- Tom Irvine

The Pierson–Moskowitz (PM) spectra is an empirical relationship that defines the distribution of energy with frequency within the ocean. The result is given as a wave height power spectra density.

Developed in 1964, the PM spectrum is one of the simplest descriptions for the energy distribution. It assumes that if the wind blows steadily for a long time over a large area, then the waves will eventually reach a point of equilibrium with the wind.

This is known as a fully developed sea. Pierson and Moskowitz developed their spectrum from measurements in the North Atlantic during 1964.

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Here is a paper: wave_height.pdf

Here is a Matlab script: ocean_wave_PSD.m

- Tom Irvine

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