PROJECT-BASED LEARNING IN UNIVERSITY PHYSICS. PROBLEM SOLVING IN ACOUSTICS

Active learning methods can be appropriate in Engineering, as their methodology promotes meta-cognition, independent learning and problem-solving skills. Understanding acoustic concepts is important for engineering students and project-based learning (PBL) involves posing a ‘specific acoustic problem’ to initiate the learning process. In this work, we describe and analyse results from two educational experiences using the project-based learning method.

The main objective of the Bachelor's Degree Final Project entitled “Study of the acoustic properties of materials using the two microphones method” was to learn to perform reliable measurements of sound absorption coefficient using the ACUPRO system of Spectronics (ISO 10534-2). The ISO 10534-2 cover the use of an impedance tube, two microphone locations and a digital frequency analysis system for the determination of the sound absorption coefficient of sound absorbers for normal sound incidence. The sound source is connected to one end of the tube and the test sample mounted at the other end. Plane waves are generated in the tube by a noise source. The decomposition of the interference field is achieved by the measurement of acoustic pressures at two fixed locations using wall-mounted microphones. Subsequently, the normal incidence absorption of the acoustic material can be calculated in the broadband approach. The activities that student completed were: experimental system assembly, absorption coefficient measurement of some materials, drafting of a manual describing in detail the experimental procedure to minimize uncertainties in the measurements obtained. The absence of reference materials for absorption coefficient makes this project useful for further measures in new materials.

The main objective of the Bachelor's Degree Final Project entitled “Characterization of the saxophone using acoustical analysis techniques” was to learn to characterize the sound of the instrument using techniques based on Fourier analysis. The saxophone is a family of wind instruments usually made of brass and played with a single-reed mouthpiece. The player controls several elements in the system, including the air pressure in the mouthpiece and the bore geometry via keys. One of the reasons that made this project attractive for the student was that it made coexist and interact aspects from several domains such as acoustics, signal processing and music. Moreover, understanding the physical operation of the instrument was useful for learning to perform the instrument. The activities that student completed were: experimental system assembly, sound recording and timbre analysis of several notes, drafting of a manual describing in detail the experimental procedure and timbre parameter calculation. Besides, the use of the Fast Fourier transform makes this project useful for many applications in engineering, science, and mathematics.

From an instructors’ perspective, PBL strengths include better student attitudes to their work and more instructor–student interaction. The students emphasised positive aspects such as developing the ability to apply the acquired knowledge and skills and working in a good learning atmosphere.