Applied Acoustics
Code
7368
Academic unit
Faculdade de Ciências e Tecnologia
Department
Departamento de Física
Credits
6.0
Teacher in charge
Carlos Jorge Mariano Miranda Dias, José Paulo Moreira dos Santos
Weekly hours
4
Total hours
65
Teaching language
Português
Objectives
1. Introduce students to the phenomenology associated to acoustics quantities
2. Acoustic signal analysis regarding its intensity, spectral content and temporal behaviour.
3. Noise characterization of acoustic environments.
4. Establishment and solution of the equation of physical acoustics with an emphasis on the notion of acosutic impedance.
5. Room acoustics and its conditioning through quantification of the reverberation time together with its frequency and spatial properties.
Prerequisites
There are no disciplines required prior to enrollment in this course. However it is assumed that student have general knowledge of mathematics and physics.
Subject matter
NATURE AND OBJECT OF ACOUSTIC WAVES
Waves and its attributes. Velocity of propagation of acosutic waves. Audible range. Principles of linearity and superposition. Sound Level. Acoustic energy and intensity. Decibel scale. Geometry and sound level. Sound absortion in the propagation medium.
SOUND DETECTION AND MEASUREMENT
Characteristics of sound waves: amplitude, frequency, phase. Transducers: microphones and speakers. Measurment of frequency and amplitude. Measurment of sound levels. Frequency weight and Sound weigthed curves.
SPECTRAL ANALYSIS
Sound pressure level. Octave and third-octave bands. Spectral analysis.
NOISE
Definition of Leq and Lepd. Noise dose. Statistical analysis of noise. Dosimeters. Nonometers. Transmission and noise reduction.
WAVELIKE PHENOMENA ASSOCIATED TO ACOUSTICS
Beats. Coherence. Interference of point sources. Difraction. Sound protecting barriers.
SOUND EQUATIONS
Definitions. State, continuity and Euler equations. Lineaized sound equation. Plane harmonic equation. Acoustic intensity and acoustic impedance. The equation for spherical and cillindrical waves.
ROOM ACOUSTICS
Types of reflections. Stationary waves in rooms. Room acoustics evaluation criteria. Uniformity in frequency and Schroeder criterium. Reverberation time: definition. Sound reverberating fields. Absorption coeffcients and its measurement. Sound reinforcement.
TUBES AND RESONATORS
Guided waves. Acoustic impedance. Inertance, compliance and acoustic resistance. Electrical and mechanical analogues. The Helmholtz resonator. Reflection and stationary waves in tubes.
Bibliography
Slides used in the course available through the MOODLE system
Fundamentals of Acoustics - L. E. Kinsler, A. R. Frey, A. B. Coppens and J. V. Sanders, John Wiley 2nd ed. 1982
Basic Acoustics - D. E. Hall, John Wiley 1987
Principles of Vibration and Sound - T. D. Rossing and N. H. Fletcher, Springer-Verlag 1995
Engineering Noise Control - D. A. Bies and C. H. Hansen, Chapman & Hall 1988
Noise Control - Bruel and Kjaer 1982
Acústica de Edificios - P. Martins da Silva, LNEC - ICT Informação Técnica, Edificios ITE 8, reimpressão1995
Teaching method
Theoretical classes with datashow. Problem solving classes with student participation.
Practicals include theory preparation, experimental procedure and production of a report.
Availability of the study material in the internet.
Evaluation method
ADMISSION TO THE EXAM: Six practicals are performed from which one is chosen to make a report (NRel) that will be discussed (D)
PASS: Two minitests are performed during the semester.
The final classification is,
N=0.3MT1+0.3MT2+0.2NRel+0.2D