Method for analyzing sound pressure and sound particle velocity using cardioid microphones

Abstract

A method for analyzing the sound pressure and sound-particle velocity in sound fields using cardioid microphones—that is, the c-c method—was developed. First, the response and directivity of a cardioid microphone were defined using the sound pressure and particle velocity in the sound field. Unlike conventional definitions, these new definitions were generalized mathematical models that did not assume a specific sound source or sound field, the c-c method algorithm being derived from these definitions. To verify the new response and directivity definitions, as well as the c-c method itself, experiments were conducted in near-sound fields where the sound pressure and particle velocity did not exhibit the same phase. Consequently, the directivity changed with distance from the sound source and frequency. This change corresponded well with the theoretical value generated using the proposed model, demonstrating the validity of the new directivity definition, even in the near-sound field. The sound-pressure and particle-velocity measurement results obtained using the c-c method corresponded well with the theoretical values. These results demonstrated the c-c method to be valid, even in the near-sound field.