93825 - Vehicle Acoustics M

Learning outcomes

The students will be able to characterize, modify and simulate the acoustic emissions of vehicles, integrating these with other technical skills. The learning outcomes include: fundamentals of acoustics; NVH analysis; vehicle noise control (with laboratory activity); acoustic virtual reality applied to vehicles (with laboratory activity); increasing the acoustic comfort on vehicles; basic knowledge of measuring equipment and technical standards.

Course contents

1. Physical Acoustics and Psychoacoustics

Main acoustic quantities: pressure, particle velocity, sound velocity, sound intensity. Acoustic impedance and electrical analogy. Wave equation and solutions with open/closed boundary conditions. Plain, spherical and cylindrical waves. Standing Waves.
Human hearing system. Monaural and binaural paths (hints).

2. Audio signal processing

Discrete-time and continuous-time Analysis. Decibel. Audio frequency analysis. FIR/IIR filters. Weighting curves: A,C,Z. Objective and subjective metrics of sound-pressure levels.

3a. Audio transducers and audio acquisition systems

Microphones. Accelerometers. Sound level meters. Real-time processing and FFT. Sound intensity meters. Audio machine-learning tools: GMM, KM, and more. Subjective judgement criteria.
Loudspeakers: electric, mechanic and acoustic model. Thiele/Small parameters, acoustic-load examples.

3a. Sound-material interaction

 Acoustic behaviour in fluid-solid matching. Sound absorption, sound reflection, sound transmission, sound diffusion. Strategies for enhancing the sound insulation. Complex-impedance of porous materials, Helmoltz resonators, Low-frequency absorbers. Acoustic metamaterials (AMMs).

4. NVH and Sound Quality

Engine-noise generation, Exhaust-system noise, Tyre-road noise. Turbulence-related noise (hints). Noise-control strategies. Standards for sound power measurement (ISO 3741), pass-by noise. ISO 362. More on asphalts and surfaces.  Muffler design, and other applications.
Measurement and analysis of Sound Quality criteria: Loudness, Sharpness, Roughness, Fluctuation Strength.

5. Virtual acoustics and simulation

Acoustic simulation of sound source and/or complex environment (laboratory). Spatial reproduction (HOA, VBAB). Virtual reproduction of a vehicle. Geometrical acoustics, including techniques to solve scattering- and diffraction-problem. Wave-based acoustic simulation (FEM/BEM/FDTD)

Readings/Bibliography

P Saha, Acoustical Materials: Solving the Challenge of Vehicle Noise, SAE International (R-442), 2021.

ML Munjal, Acoustics Of Ducts And Mufflers, Wiley, 2021.

Y Wang, H Guo, C Yang, Vehicle Interior Sound Quality Analysis, Evaluation and Control, Springer 2023.

U Sandberg, JA Ejsmont, Tyre-road noise reference book, Kisa: Informex, 2002.

LL Beranek (editor), Noise and vibration control, Revised Edition, Institute of Noise Control Engineering, Washington DC, 1988.

L Cremer and HA Müller, Principles and Applications of Room Acoustics (II), Peninsula Publishing, 1984.

J Blauert, Communication Acoustics, Springer, 2005

Teaching methods

Lectures, in presence. Laboratory activities, using measuring equipment and specialized software.

Seminars/Webinar by professional acousticians.

Assessment methods

Development of a case-study, including a numerical application (coding/measurement/....). The case study can be presented by a single student or a group (up to 2 persons). 
Students' final judgement will be refined by further oral examination.

Teaching tools

slides and more on virtuale.unibo.it

Office hours

See the website of Dario D'Orazio