93825 - ACUSTICA DEL VEICOLO M

Academic Year 2023/2024

  • Docente: Dario D'Orazio
  • Credits:: 6
  • SSD: ING-IND/11
  • Language: Italian
  • Teaching Mode: Traditional lectures
  • Campus: Bologna
  • Corso: Second cycle degree programme (LM) in Mechanical Engineering (cod. 5724)

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 3 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

SDGs

Quality education Industry, innovation and infrastructure

This teaching activity contributes to the achievement of the Sustainable Development Goals of the UN 2030 Agenda.