Host: The Japan Society of Mechanical Engineers
Name : Dynamics and Design Conference 2018
Date : August 28, 2018 - August 31, 2018
I am now developing a new sound localization method, Double Near-field Acoustic Holography (DNAH) method. This method is aimed to improve the resolution of low frequency sound localization. This DNAH method is converted method of conventional Near-field Acoustic Holography (NAH) method. The NAH method is said as it has best resolution in the current sound localization methods. However, the resolution of low frequency sound localization is not enough to localize the position of sound sources. In the former paper, the improved resolution of DNAH method in low frequency sound localization is proved by numerical simulations and basic experiments. By the basic experiments, the reconstructed images by DNAH method show better resolution than the images by NAH method.
In the proposing DNAH method, the measurement plane of NAH method is doubled. By the reason of doubled measurement planes, the microphone array system which can measure the sound pressure datum at all measurement points simultaneously, is not usable. Therefore, the scanning type measurement system should be used. Actually, in my laboratory, the scanning type measurement system is used for measurement of sound pressure distribution on the doubled measurement planes in DNAH method. Because of doubled measurement planes, two microphones are attached to the microphone traverse system. These microphones are characterized independently. Therefore, in DNAH method, the difference between two microphones sometimes occur problems. On the other hand, the intensity probe which is made by two microphones is widely used for acoustic measurement, measuring acoustic intensity. Since this intensity probe is one product, the calibration between two microphones are completely done by its producer.
The length between two microphones in measurement of DNH method in former research is about 0.2m. In this setting, the predominance of DNAH method is verified in former paper. On the other hand, the gap between two microphones in the intensity probe is about 0.02m. If the measurement of DNAH method can be done with 0.02m gap, the preciseness of experiments may be consolidated.
In this paper, the experimentations with variated gap between two microphones, two measurement planes are carried out. As a results, it is verified that the predominance of DNAH method is not change with the gap between two microphones.
