声激励简单导管的声辐射特性研究

采用NASTRAN无限元技术,对简单导管受声激励的声辐射特性进行了研究,建立了导管声波模态和辐射声能量之间的直接联系,并考虑了导管半径、长度、长径比三种因素对管内声波模态、管外辐射声功率和远场声指向性的影响。研究结果表明:影响导管声波模态和辐射声功率的参数主要有两个,一是无因次波数,二是导管长径比;导管的长径比越小,总辐射声能量变小,但侧方屏蔽效应也变差,因此需综合考虑长径比变化对总辐射声能量和声指向性的影响;和导管的侧方屏蔽效应主要作用于中高频,低频时导管外的声场与入射声场基本相同。

Study of sound radiation of a simple duct excited by sound source

Based on NASTRAN infinite element technology, the sound radiation of a simple duct excited by sound source was studied detailedly. The relationship between wave mode and radiated energy was founded, and the influence of the duct's radius, length, length-to-diameter ratio on wave mode, radiated power and directivity of far field was considered. The results show that: there are two parameters that affect duct's wave mode and radiated power, the non-dimensional wave number and the length-to-diameter ratio; and with the ratio becomes smaller, the radiated power becomes smaller, and the lateral shielding effect becomes weaker. It should be considered comprehensively to choose proper size of duct for the best effects of sound power reduction and lateral shielding; the lateral shielding effects act on high frequency band rather than low frequency band.