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Scheda Riassuntiva
Anno Accademico 2017/2018
Scuola Scuola di Ingegneria Industriale e dell'Informazione
Insegnamento 097468 - NOISE AND VIBRATION ENGINEERING
Docente Corradi Roberto
Cfu 5.00 Tipo insegnamento Monodisciplinare

Corso di Studi Codice Piano di Studio preventivamente approvato Da (compreso) A (escluso) Insegnamento
Ing Ind - Inf (Mag.)(ord. 270) - BV (483) MECHANICAL ENGINEERING - INGEGNERIA MECCANICA*AZZZZ097560 - NOISE AND VIBRATION ENGINEERING
Ing Ind - Inf (Mag.)(ord. 270) - MI (473) AUTOMATION AND CONTROL ENGINEERING - INGEGNERIA DELL'AUTOMAZIONE*AZZZZ097468 - NOISE AND VIBRATION ENGINEERING

Programma dettagliato e risultati di apprendimento attesi

Course overview

The course is an advanced module on mechanical vibrations and related noise generation phenomena. In the first part, the analysis of vibration in one-dimensional continuous systems, previously introduced in the course Dynamics of Mechanical Systems, is extended to the two-dimensional case. The second part of the course deals with sound waves and sound radiation from vibrating structures. Finally, the third part of the course is devoted to engineering applications, to experimental techniques and to numerical methods for vibroacoustic modelling.

 

Syllabus

Vibration and waves in one-dimensional continuous systems. Review of the partial differential equation governing transverse vibration of stretched strings and axial vibration of bars (one-dimensional wave equation). Traveling waves vs. 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, phase and group velocities, point mobility. Bending vibration of finite plates. Vibration modes of rectangular and circular plates with different boundary conditions (analytical and finite-element numerical solutions).

Sound waves. Derivation of 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.

Sound radiation from vibrating structures. General formulation of the vibroacoustic problem. Sound radiation from an infinite plate. Wave/boundary matching. Critical frequency. Sound radiation from finite plates. Radiation efficiency. Reciprocity principle. Mechanical and acoustic excitation.

Experimental techniques in vibroacoustics. Fundamentals of experimental modal analysis: test equipment and test procedure, data processing and identification algorithms. Sound intensity and sound power measurement techniques. Introduction to sound source mapping through microphone arrays. Practical examples.

Numerical methods in vibroacoustics. Introduction to finite-element and boundary-element methods for the simulation of the sound field in case of an acoustic enclosure and of free-field radiation. Statement of the problem and corresponding numerical formulation. Examples of application.

Noise and vibration mitigation measures. Overview of noise and vibration transfer mechanisms. Mitigation measures at the source, along the transmission path, at the receiver. Sound transmission through partitions: transmission loss, noise reduction. Acoustic enclosures: insertion loss, design criteria.


Note Sulla Modalità di valutazione

Course organization and examination

In addition to traditional lectures and class exercises, the course includes experimental labs and numerical simulation sessions in computer room (4 in total), focused on specific methodologies, case studies or practical applications. Students are requested to prepare short reports on these activities, to be delivered at the final exam. The examination consists in an oral test only.


Bibliografia
Risorsa bibliografica obbligatoriaNorton, M. P., Fundamentals of noise and vibration analysis for engineers, Editore: Cambridge University Press
Risorsa bibliografica facoltativaSoedel, W., Vibrations of shells and plates, Editore: Marcel Dekker
Risorsa bibliografica facoltativaNilsson, A. and Liu, B., Vibro-acoustics (Vol.1-2), Editore: Springer-Verlag
Risorsa bibliografica facoltativaFahy, F., Foundations of Engineering Acoustics, Editore: Academic Press
Risorsa bibliografica facoltativaFahy, F. and Walker, J., Advanced Applications in Acoustics, Noise and Vibration, Editore: Spon Press

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Mix Forme Didattiche
Tipo Forma Didattica Ore didattiche
lezione
34.0
esercitazione
10.0
laboratorio informatico
8.0
laboratorio sperimentale
6.0
progetto
0.0
laboratorio di progetto
0.0

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schedaincarico v. 1.7.2 / 1.7.2
Area Servizi ICT
30/09/2022