Ing Ind - Inf (Mag.)(ord. 270) - BV (483) MECHANICAL ENGINEERING - INGEGNERIA MECCANICA
097560 - NOISE AND VIBRATION ENGINEERING
Ing Ind - Inf (Mag.)(ord. 270) - MI (473) AUTOMATION AND CONTROL ENGINEERING - INGEGNERIA DELL'AUTOMAZIONE
097468 - NOISE AND VIBRATION ENGINEERING
The aim of the course is to enable students to master advanced engineering methods for analysing noise and vibration problems, with a specific focus on industrial and transportation applications. The course covers fundamental analytical models, experimental techniques and numerical methods. Each topic is treated both theoretically and practically, through traditional lectures and experimental/computer labs.
Risultati di apprendimento attesi
The course will provide students with:
a knowledge of the modelling approaches to vibration and wave propagation analysis of one-dimensional and two-dimensional continuous systems (DD1);
a knowledge of sound waves, acoustic quantities and wave propagation models (DD1);
an understanding of the basic physical principles of sound radiation and sound transmission (DD1);
the ability to apply theoretical knowledge to the handling of complex vibroacoustic problems in real structures (DD2, DD3);
the ability to perform standard vibroacoustic measurements and to critically apply data processing techniques (DD2, DD3);
an opportunity to develop skills in summarizing and presenting the results achieved during lab activities (DD4).
Vibration and waves in one-dimensional continuous systems
Review of the partial differential equation governing transverse vibration of strings and axial vibration of bars (one-dimensional wave equation). Traveling waves and standing waves. Wave propagation speed, wavenumber, mechanical impedance. Transmission and reflection at an impedance change. Review of the partial differential equation governing bending vibration of slender beams (Euler-Bernoulli beam). Dispersion, phase and group velocities, evanescent waves.
Vibration and waves in two-dimensional continuous systems
The partial differential equation governing bending vibration of thin plates (Kirchhoff plate). Bending waves propagation, the wavenumber vector, point mobility. Bending vibration of finite plates. Vibration modes of rectangular and circular plates with different boundary conditions (analytical and finite-element numerical solutions).
The homogeneous acoustic wave equation. Sound pressure, particle velocity and acoustic velocity potential. Propagation of plane and spherical sound waves. Acoustic impedance. Far-field and near-field. Sound intensity and sound power. Fundamental acoustic source models. Directivity. The description of sound through levels, decibels and frequency-band spectra. Sound perception and weighting networks. Acoustics of enclosed spaces: direct and reverberant field, average sound absorption coefficient of a room, reverberation time.
Interaction between sound waves and solid structures
Sound radiation from vibrating structures: formulation of the problem, the Kirchhoff-Helmholtz integral equation, sound radiation from an infinite plate, wave/boundary matching, critical frequency, sound radiation from finite plates, radiation efficiency, Rayleigh’s equation.
Sound transmission through partitions: sound transmission through a single rigid panel subjected to a normally incident plane wave, sound transmission through a single flexible panel in case of obliquely incident plane wave and diffuse incident field, transmission loss, double-leaf panels, sound transmission from one room to another, noise reduction.
Sound pressure and sound intensity measurement techniques. Test equipment and test environment. Anechoic and hemi-anechoic chambers, reverberation chambers. Methodologies for estimating sound intensity and sound power levels of noise sources.
Introduction to finite-element and boundary-element methods for sound field simulation in case of an acoustic enclosure and of free-field radiation. Statement of the problem and corresponding numerical formulation. Examples.
Engineering applications and noise and vibration mitigation
Overview of noise and vibration transfer mechanisms. Mitigation measures at the source, along the transmission path, at the receiver. Transportation noise: railway noise (issues, common mitigation measures, a simple model of wheelset-track dynamic interaction) and tyre/road noise (generation mechanisms, design criteria, pass-by homologation test).
The topics covered by the course on Mechanical Systems Dynamics are prerequisites to this module on Noise and Vibration Engineering. However students with a different background are welcome and the lecturer is available for verifying with interested students the possibility for them to successfully attend the course.
Modalità di valutazione
In addition to traditional lectures, the course includes experimental and computer labs, focused on specific methodologies, case studies or practical applications. Students are requested to prepare short reports on the assignments given during the labs, to be delivered at the final exam. The exam consists of an oral test and a discussion on lab reports.
With reference to the expected learning outcomes: the oral exam is intended to verify items 1, 2 and 3, while items 4, 5 and 6 will be checked during the discussion on lab reports.
Course handouts available on BeePhttps://beep.metid.polimi.it/M.P. Norton, Fundamentals of noise and vibration analysis for engineers, Editore: Cambridge University Press, Anno edizione: 2010
W. Soedel, Vibrations of shells and plates, Editore: Marcel Dekker, Anno edizione: 1981
F. Fahy and D. Thompson, Fundamentals of sound and vibration, Editore: CRC Press, Anno edizione: 2015
A. Nilsson and B. Liu, Vibro-acoustics, Editore: Springer-Verlag, Anno edizione: 2016
F. Fahy and J. Walker, Advanced applications in acoustics, noise and vibration, Editore: Spon Press, Anno edizione: 2004
Tipo Forma Didattica
Ore di attività svolte in aula
Ore di studio autonome
Laboratorio Di Progetto
Informazioni in lingua inglese a supporto dell'internazionalizzazione
Insegnamento erogato in lingua
Disponibilità di materiale didattico/slides in lingua inglese
Disponibilità di libri di testo/bibliografia in lingua inglese
Possibilità di sostenere l'esame in lingua inglese
Disponibilità di supporto didattico in lingua inglese