Software Development Of Sound Source Identification System Based On Near-field Acoustic Holography

The correct identification and localization of sound source is the key step to control the spread of sound from equipment or structures.After a long time of development,the Near-field Acoustic Holography(NAH)has been widely used in close distant measurement and identification of low and medium frequency noise sources.But conventional NAH method can only be applied under the free-field conditions,in addition to that all the sound sources must be on the same side of the measurement array,so does the existing noise source identification software system based on NAH method.As a general holographic measurement usually cannot been provided with a free-field condition,the sound field reconstruction result can not be accurate enough.To sum up,we have a great need for an accurate sound source identification system that can be applied to reconstruct sound field in the free-field and non-free-field cases.In order to achieve non-free field application scenarios,based on the superposition theory of the spherical harmonics with different expansion orders and the single layer microphone array based sound wave separation method,the main aim of this dissertation's work is to develop a sound source identification software system on LabVIEW platform so as to perform the identification of sound source under both free field and non-free field condition.The main work of this dissertation is as follows:(1)Present the theoretical derivation and calculation algorithm of the spherical wave superposition based sound field reconstruction and the single layer microphone array based sound field separation method,and give a general guideline for how determine the optimal number of expansion functions.(2)Develop a complete sound source identification software system with modular programming in the LabVIEW platform.Integrated with the NI hardware system,the software functions such as sound field data acquisition,sound field reconstruction and sound wave separation calculations,data processing,visualization of acoustic field and data storage are implemented.(3)Verify the system function modules with the examples of simulations and experiments,check the accuracy of the system and determine the system parameters' range according to the results of the examples of the simulations and experiments.