Cóser, L., Oliveira, A., and F.Arruda, J., "Experimental Validation of Simple Acoustic Sources using a 3D System for P-P Intensimetry," SAE Technical Paper 2015-36-0107, 2015, doi:10.4271/2015-36-0107.
Simple and complex sound sources can be constructed using loudspeakers assembled on the surfaces of platonic solids such as the cube and the dodecahedron, whose implicit mathematical properties enable their application in acoustic radiation studies. By using special phase combinations of the electric signals applied to each loudspeaker, complex sound fields can be produced with their distinct spatial patterns. In many applications (such as aeroacoustics of cars and airplanes) monopoles, dipoles and quadrupoles are sufficient in the investigation of acoustic phenomena. Their experimental validation is usually performed using a circular microphone array to measure the sound pressure field around the test object. This approach can be very complicated and poses many challenges in terms of test setup, execution and post-processing. Therefore, there is a need for new experimental methods to characterize acoustic sources. This work presents the results from an alternative method using a 3D measurement system for sound intensity measurement based on a p-p intensity probe. Known as SoundBrush®, it can measure in real time both the sound pressure and sound intensity fields in a very convenient way. In this work, a cubic speaker array was constructed to generate acoustic dipoles and quadrupoles at different operating frequencies. The properties of their radiated sound fields were then determined and, although limited to 4 kHz and to the study of stationary phenomena, the technique proved to be very effective not only for the verification of the sound pressure field predicted by the simulations, but also for the acoustic intensity field. Finally, the methodology can be extended to more complex sound sources such as radiating structures commonly found in transportation vehicles, of which the produced sound fields are usually very complicated to visualize, understand and validate.