MEASURING THE SOUND FIELD INSIDE A LARGE SPACECRAFT ACOUSTIC TEST CHAMBER

摘要

Space flight hardware is frequently tested for its vibrational response to the types of high sound pressure levels that might be encountered during the launch stage. The flight hardware is placed in a large reverberant chamber and is exposed to high sound pressure random noise. The vibrational response measured can then be compared to that predicted via a number of standard modeling techniques. These models use the conventional assumption that the sound field inside the test chamber is diffuse. However, this assumption has never been put to the test and unpredicted vibrational responses are not uncommon. In November 2008, a large (50,000 cubic foot) acoustic test facility was measured and mapped over a period of 3 days. This was done by moving a 100 microphone array throughout the chamber volume while operating the chamber. A 3 dimensional sound pressure map was produced, offering a stunning view of something never before seen. The map showed that indeed the sound field was not as diffuse as expected. This paper shows how the 3 dimensional sound field was mapped and shows some of the results obtained. It concludes by discussing how future testing might be improved armed with this new knowledge at this particular acoustic test facility.