B6376 - Acoustics

Learning outcomes

Through the Integrated Course COMFORT RELATED TO SOUND AND VIBRATION, the student acquires fundamental knowledge of airborne acoustic waves and their perception by humans, as well as of mechanical vibrations and the associated challenges in marine engineering. The course provides the theoretical and practical foundations necessary to define, quantify, and measure the principal acoustic and vibrational parameters using standardized methodologies. Students develop competence in signal analysis within both the time and frequency domains, and gain familiarity with the principles of experimental modal analysis applied to naval structures and components. The course also covers the selection and application of acoustic materials in accordance with international technical standards. Finally, the student learns to evaluate and implement engineering solutions for noise control and for the reduction and isolation of vibrations in vessels, with the aim of improving onboard comfort.

Course contents

1. Fundamental concepts of physical acoustics and psychoacoustics
Main acoustic quantities (pressure, particle velocity, speed of sound, intensity, etc.). Acoustic impedances and electrical analogy. Acoustic wave equation and its solutions. Overview of the functioning of the human auditory system. Introduction to psychoacoustics.

2. Introduction to acoustic signalprocessing
Characteristics of sound signals. Decibel scale. Introduction to frequency analysis. Spectra. Filters. Weighting curves. Measurement of sound levels. ISO 2923. Sound Quality parameters ISO 532-1.

3. Instrumentation for acoustic measurements
Calibrated measurement chains, measurement uncertainty (ISO/IEC Guide 98-3:2008). Uncalibrated measurement chains: sound level meter, beamforming (overview).

4. Sound-Material Interaction
Acoustic absorption: fundamental laws and control mechanisms. Acoustic insulation: fundamental laws and control mechanisms. Materials for acoustics: porous materials, membrane and cavity resonators, microperforated materials, acoustic metamaterials.

5. Noise Control on Boats
Identification and characterization of noise sources: propulsion and exhaust noise, hydrodynamic and aerodynamic noise, Source-Path-Receiver modeling. Predictive methods. Numerical modeling (overview). Solutions for noise control on boats. Guidelines for comfort (IMO A458, MLC, ABS, RINA, BV, DNV GL, LR).

Readings/Bibliography

Handouts provided by the teacher on https://virtuale.unibo.it

Further reading: Fisher, Boroditsky: “Noise and Vibration Control on Ships. Understanding and Cutting Through the Noise”, Springer, 2024.

Teaching methods

Lectures and any experimental activities in the laboratory/on site.

Assessment methods

The final exam is oral and includes questions aimed at assessing the acquisition of the knowledge outlined in the course syllabus and evaluating the achievement of the educational objectives.

Teaching tools

Blackboard, PC, projector.

Office hours

See the website of Federica Morandi