22 - 24 October 2019

Acoustics plays a major role in designing of mechanical systems. There are three main reasons for doing Acoustic simulations:

  • Legal Requirements for noise levels (e.g. Pass-By Noise)
  • Human Comfort & delight (e.g. Design of car & aircraft interiors, Exhaust Signature noise)
  • Failure of components due to acoustic excitations (e.g. Aircraft liners, fan blades).

The acoustic simulations are quite complex since it involves multi-physics i.e. vibration of the component, air/fluid flow over or within the components, changes in temperature gradient etc. and many other parameters. Hence, in order to get correct results & confidence in simulations, it becomes very important to understand the physics & the mathematics behind the problem.

This course would help users gain confidence in the simulations & achieve a better correlation with test. It will also help finding quicker, cost effective & practical solutions to the acoustic problems.



Course Location

Free Field Technologies HQ
9 rue Emile Francqui
1435 Mont-Saint-Guibert
Belgium


Course Fees

2500 €/- per participant *
* Taxes extra




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Expert Profile

Dr. Jean-Louis Migeot, PhD
Founder – Free Field Technologies




Dr. Jean-Louis Migeot holds a PhD in Acoustics from the University of Brussels and an MBA from the same university. He has spent his entire career in CAE, first in vibration analysis while working for SDRC, then in acoustics when he joined Numerical Integration Technologies. In 1998, he co-founded Free Field Technologies with Jean-Pierre Coyette and made the company a leader in the field of acoustic CAE.
Dr. Jean-Louis Migeot also teaches Acoustics at the University of Brussels and at the Royal Music Conservatory of Liège
. He is member of the Belgian Royal Academy of Sciences, Humanities and Arts.
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Course Content

Day 1

Session 1
   
Overview of acoustics: definitions, fields, relevance

• Definition of sound
• Overview of the many fields of acoustics
• Discussion on the importance of noise pollution and acoustic design in today’s
world

Session 2 From Navier-Stokes to the wave equation
• Navier-Stokes equations
• Fundamental physical hypothesis of acoustics
• d’Alembert’s wave equation
• 1-D solution
• Why do sound propagate?
• Speed of sound in various media
• Relationship between key wave indicators: speed, wavelength, wave number,
pulsation, period, frequency
• Dispersive and non-dispersive propagation

Session 3 Fundamentals of Fourier theory and frequency analysis
• Combination of two monochromatic (pure tone) sounds of identical frequency
• Introduction to active noise control
• Combination of two monochromatic (pure tone) sounds of different frequency
• Fourier analysis and synthesis
• Complex amplitudes of sound waves (phasors)
• From Fourier series to Fourier transforms
• Main properties of the Fourier transform
• Filtering and Windowing

Session 4 Helmholtz equation and acoustic levels
• Helmholtz equation
• Pressure and velocity spectra
• Active and reactive intensity and intensity measurements
• Acoustic impedance and admittance
• Plane waves and spherical waves
• Sound pressure, power and intensity levels
• Fletcher and Munson experiments and A-B-C-D fltering
• Frequency bands and band levels
• White, pink and brown noise
• Equivalent and statistical sound levels
• NR-curves


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Day 2

Session 5     
Sound reflection and room acoustics
• Reflection of a plane wave on a rigid surface and on a free surface
• Absorption at the surface: acoustic impedance, reflection and absorption coefficient
• Effect of angle of incidence (Descartes law)
• Reflection of spherical waves
• Echograms, acoustic rays, ray tracing method
• Reverberation time and Sabine law
• Anechoic room, semi-anechoic rooms, reverberant chamber
• Acoustic resonances

Session 6
Introduction to Simulation and acoustic resonance workshop
Workshop: Computing the acoustic modes and resonance frequencies of a cavity
Session 7
Guided wave propagation and duct acoustics
• Waves in ducts: cut-off frequency
• Plane wave approximation and transfer matrices (TM)
• TM of a simple tube
• TM of an expansion
• Transmission loss
• Resonators (quarter-wavelength and Helmholtz)
• Pressure and velocity sources
• Insertion Loss
• Three different noise sources in silencers: tailpipe noise, flow noise and shell
noise

Workshop:
Calculation of the transmission loss of a simple muffler
Session 8
Sound radiation and directivity analysis
• Directivity diagrams
• Monopoles, dipoles, quadrupoles
• Multipole analysis
• Near feld and far feld
• A-dimensional distance (Helmholtz number)
• Effect of frequency on directivity
• Helmholtz integral equation
• Application to loudspeakers

Workshop Sound radiation by a vibrating structure (automotive powertrain)
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Day 3

Session 9
   
Fluid-structure interaction and sound transmission analysis


• Defnition of sound
• Overview of the many felds of acoustics
• Discussion on the importance of noise pollution and acoustic design in today’s world
Workshop: Low frequency transmission through a flexible structure

Session 10

Acoustic materials
  • The physics of porous material
• Kundt’s tube and other measurement devices
• Biot theory
• Sandwich structures
• Free vs. constrained layer damping
• Layered windshield with visco-elastic core

Session 11 Aero-acoustics and convected wave propagation
Convected wave propagation:
• Prandtl-Glauert transformation
• Doppler effect
• Potential flows
• General flow; linearized Euler equations
• Application to aircraft engines
• Atmospheric propagation and effect of wind on long distance sound
propagation
Aero-acoustics:
• Fan noise models
• Lighthill and Möhring’s analogy
• SNGR technology
• Presentation of various applications: wind noise, air-conditioning noise, etc

Session 12 Numerical methods in acoustics
• The fnite element method in acoustics: fnite element, infnite element,
(automated) perfectly matched layer
• The boundary element method in acoustics
• A brief introduction to statistical energy analysis
• All methods will be illustrated by many examples