Learning outcomes of the course unit
Knowledge and understanding:
For students of all branches of engineering this is a key course, it is practically the only opportunity to see (or, rather, hear) the techniques learned in previous courses, in which the purely theoretical foundations of modern advanced mathematical methods are taught. When the "numbers" are transformed into sound, abstruse and difficult mathematical procedures (such as differentiation and integration) quickly become very clear and immediate, and the possibilities offered by sound editing systems on the PC, used extensively both during lectures and during laboratory exercises, make it possible to listen immediately (usually in real time) to the "effects" of filters or other devices (compressors, gates, convolvers, denoising, etc.).
Applying knowledge and understanding:
The course is tailored to practical application, not to theoretical knowledge. Great emphasis is given to measurement methods, simple computations performed in Excel, and solution of practical problems. The student will learn to use the decibel scale, to “think in decibels”, and to perform the common math operations on dB values.
In the whole course the judgment method is always based on human listening experience, not on numerical evaluation of the results. Acoustics is a perceptual science, and the final judgement can only by given by our hearing system, and not by means of “objective” numerical quantities. The students are consequently trained to listen and evaluate perceptually the most relevant acoustical effects, such as frequency-domain filtering, reverberation, echo, noise contamination, etc.
The goal of this course is not, definitely, to train the students to perform as actors on stage. However, a significant part of the course is devoted to the study of the verbal and musical communication between performers and audience. In this part of the course, the students learn some tricks employed by professional actors and musicians, and become skilled in diagnosis and correction of communication problems due to room acoustics, improper design of the electro-acoustical systems, or improper use of them by the performers and the audience.
Course contents summary
The course of Applied Acoustics is an introductory course to a scientific and technological field undergoing a very rapid development, which offers great employment opportunities, and which involves disciplines apparently very different: architecture, structural engineering, physiology, psychology, statistics, physics, electronics, vibration mechanics, fluid dynamics, digital signal processing, telecommunications, measurements, hygiene of the workplace, music, musicology, virtual reality.
Because of its multidisciplinary nature, the Course of Applied Acoustics is attended by students from various degree programs (almost all branches of Engineering, but also some Architecture students).Obviously in a course of 6 CFUs we can only provide the methodological basis of the topic, which must then be furthered in more in-depth courses.
Definition of quantities. Propagation of mechanical disturbances in an elastic medium.
Sound pressure and particle velocity. The speed of sound.
The wave equation.
Sound intensity and sound energy density. Active and reactive intensity. Propagating and stationary sound fields.
Physiological and psychological mechanisms of sound perception by humans.
The logarithmic scale of decibels (dB), elementary operations on quantities expressed in dB. Frequency weighting curves.
Masking phenomena in time and in frequency. Audio compression algorithms based on psychoacoustic principles.
Plane waves, spherical waves, standing waves. Sound reflection and absorption.
Sound propagation outdoor.
Room acoustics: reverberation, sound quality in concert halls and opera houses, ISO3382 acoustical parameters.
Advanced methods for impulse response measurement.
Digital Signal Processing applied to audio and acoustics.
Fundamentals of spectral analysis and Fourier transform.
Sampling of signals.
The DFT and the FFT algorithms. Convolution.
FIR and IIR filters, calculation of Inverse numerical filters.
Active control of sound.
Virtual acoustics and 3D audio.
Electroacoustics and instrumentation for acoustic measurements:
Acoustic transducers (microphones, loudspeakers).
Devices for processing analog and digital acoustic signals: amplifiers, equalizers, reverbs, compressors, etc...
Sound level meters, spectrum analysers, impulse response measurement systems.
Virtual Instrumentation on PC and software for acoustical measurements, with practical experiments.
Techniques for numerical simulation of sound propagation:
Fundamental of finite element methods, boundary element methods, and ray tracing.
The recommended textbooks for an introduction to this topic are:
P. Fausti: Acustica in Edilizia , Rockwool, Italy, Milan, 2005 (free download in PDF format)
R. Spagnolo: Acustica: Fondamenti e applicazioni, UTET Università, 2015, ISBN: 9788860084460
T. D. Rossing (ed.): Springer Handbook of Acoustics, Springer Science+Business Media, New York, 2014
L.E. Kinsler, A.R. Frey, A.B. Coppens, and J.V. Sanders: Fundamentals of Acoustics, Wiley & Sons, 2000
F. Fahy: Foundations of Engineering Acoustics, Academic Press, 2000,
The course includes a combination of frontal lectures and workshop/laboratories.
The theoretical background of the material covered by this module will be explained during frontal lectures. Computer-based and practical demonstrations will often be used during lectures to demonstrate the practical aspects of this discipline.
Hands-on workshop or laboratories, with the aid of computers or measurement equipment, will also be carried out to allow students to familiarise themselves with numerical simulations and signal processing and with experimental measurements.
Class tests will be carried as formative or summative assessment to monitor and evaluate student progress.
Assessment methods and criteria
The assessment consists of two separate tests:
1) a written examination, consisting of a number of exercises. Some students may be exempted from the written test, on the basis of the results obtained during in-class tests.
2) Oral examination, which focuses mainly on theoretical topics, and which can be accessed only after passing the written test.