Learning outcomes of the course unit
The course is aimed to providing just a basic level of knowledge on Acoustics. For becoming a professional acoustician, the student will need to be further trained after the degree, as the minimum duration of a serious training in Acoustics is 160 hours or 20 CFU.
No previous knowledge about acoustics and digital signal processing is required for following this course, which starts from a basic level.
Course contents summary
The course provides an overview of Acoustics, form basic physical facts and definitiosn, up to advanced methods implemented by means of digital signal prossing.
Phisical Acoustics: definition of the quantities, propagation of mechanical perturbations in an elastic medium: sound pressure, particle velocity, sound wave speed. Acoustical wave equation.
Energetic Acoustics: sound propagation view as energy transport. Definition of Acoustic Intensity, and Sound Energy Density. Active and reactive energy, traveling and stationary sound fields. The sound energy speed, the reactivity index.
Sound propagation: Outodoor acoustics: gorund absorption, effects of temperature gradient and wind, shielding due to obstacles. The Maekawa and Kurze-Anderson formulas for estimating the sound reduction obtained by a noise barrier.
Indoor acoustics: multiple reflections, stationary reverberant field. Equation of the reverberant and of the semi-reverberant field. Transient phenomena occurring when switching on or off the sound soruce: the sound tail, the impulse response of a room, Schroeder’s backward integration. Definition of the reverberation time and of the other acoustical parameters related to time transients. Sabine’s Eyring’s and millington’s formulas for estimating the reverberation time. Apparent acoustic absorption coefficient, and measurement of it inside a reverberant room.
Sound propagation through bulding’s structures: sound insulation of walls, windows, sound impact insulation of floors. Measurement technique and Italian legislation.
Electroacoustics: transduction between electrical and acoustical signals, microphones, loudspeakers. Analog and digital processing of the acoustical signal: amplifiers, equalizers, reverb units, compressors, etc. . Applications to consumer electronics, telecommunication systems, broadcasting systems, recording and media industries, automeotive industry, aeronautics and naval applications.
Numerical simulation of the sound propgation: models based on finite elements, boundary elements, ray tracing, beam tracing. Practical usage of simulation software. Auralization, virtual acoustics reality. Modern applications to entertainment industry and musical performances, future developments about real-time, “live” usage.
Instrumentation and equipment for acoustical measurements: sound level meter, spectrum analyzer, impulse response measurement system. Virtual instruments implemented on PC, software for acoustical measurements, with practical training in the lab.
Numerical acoustic signal processing: from general theory to practical applications running on the PC. The “plugins” employed for numerical acoustics effects, development of code for practical implementation of real-time processing algorithms exploiting the techniques already learned in previous courses: FIR and IIR filters, fast convolution by FFT processing, computation of numerical inverse filters, active sound cancellation, with practical training in the lab.
Acoustical imaging and applications for underwater sonar, medical imaging, acoustical tomography and holography.
R. Spagnolo - Manuale di Acustica applicata, 2001, Anno ristampa 2005, pp.928 € 46.00 Editore: UTETLIBRERIA
S. Cingolani, R. Spagnolo - Acustica musicale e architettonica 2004, pp.992 € 45.00 Editore: UTETLIBRERIA
Lessons are held in a classroom equipped with a beamer, which is employed both for Powerpoint presentations (which are made available on the web site of the course) and for employing interactively a number of sound procssing programs, together with loudspeakers, microphones, and other equipment.
At the end of the course, two training sessions are done inside a lab, where each student performs eloctroacoustical measurements and computer simulations of sound propagation.
Assessment methods and criteria
Oral examination, but students who took part to the lab training will present a small technical report, which can be evaluated for 3 additional CFUs.
Since academic year 2010/20111, the frontal lessons are recorded, and the resulting AVI files can be downloaded from the web site of the Applied Acoustics course.