May 28th-29th, 2018
Presenter: Prof. Dr. Wolfgang Klippel and Dipl. Ing. Christian Bellmann
Schedule: 9:00a.m. – 5:00p.m.
This Seminar is dedicated to the evaluation of the sound field in the 3D space (near and far field) and the relationship to the mechanical vibration on the sound radiating surface (cone, surround, panel, enclosure).
The first day starts with the measurement of the directional characteristics based on direct far field measurements and holographic near field scanning. The seminar shows in practical hands-on measurements how to measure the complex transfer functions with sufficient angular resolution and accuracy in a minimum measurement time while coping with imperfect measurement conditions (sound reflections, room modes baffle diffraction, insufficient distance, inhomogeneous distribution of air temperature, ambient noise, …). The new possibilities provided by near field scanning and holographic processing are illustrated on different loudspeaker systems including consumer and professional equipment (e.g. line arrays) and transducers in small baffles. This new technique provides highly accurate data not only for system design, installation and stage application but can be also used to calibrate small anechoic rooms and to perform simulated free field measurements in a non-anechoic environment (workshop, office, EOL test box,…).
The second day explains the sound radiation on the vibrating surface while using modal vibration analysis and other analysis techniques based on laser vibrometry. Those information are required to understand acoustical cancelations and to cope with undesired rocking modes on flat speakers, headphones and microspeakers. The seminar also addresses the optimal measurement of the material parameter and the verification of Finite Element Analysis and the practical verification of those results. Finally, the relationship nonlinear modal vibration and the relationship to the harmonic and intermodulation distortion found in the acoustical output are discussed.