Author(s): Brezas Spyros, Wittstock Volker
For the establishment of traceability in sound power measurements, two major types of sound sources are proposed to be used. The first is a primary source which is a baffled vibrating body. The second source type is called transfer source, and it generates sound aerodynamically. It is planned to calibrate transfer sources by comparison with the primary source by applying an enveloping surface method using sound pressure. Therefore, the sound field created by a primary source and three transfer sources was measured in terms of sound pressure over a fully enveloping hemisphere. The measured sound pressure values formed the basis for the sound field decomposition by implementing a spherical harmonics transform. This enabled the detailed visualization of the sound pressure distribution over each source. The emission characteristics described by the spherical harmonics order were compared to the corresponding characteristics determined from measurements at various ambient temperatures, and the results are presented.
Name: Mr Spyros Brezas