RESEARCH AND TECHNICAL NOTES FOCUSED GAIN OF FOCUSED LIQUID-FILLED SPHERE AND ITS FREQUENCY RESPONSE AS A FUNCTION OF PULSE LENGTH AND WALL THICKNESS OF SPHERE

The focused liquid-filled sphere can be used for a variety of purposes,for example,measure-ment of underwater sound,test and calibration of underwater sound equipment and training of pro-fessional personnel,etc.Work in the past was done only in the case of short pulse,whereas longpulse is usually used in practice. In this paper the focused gain for the focused liquid-filled sphere as a function of frequencywas investigated for different pulse lengths.Equations for outstanding gain differences were derived,and relevant experiments were done.Experimental results are in agreement with theoretical calcula-tion.We have come to the conclusion that in order to obtain larger target strength and better fre-quency response we must raise the short pulse focused gain g_s of the liquid-filled sphere as muchas possible. Experiments of focused gain as a function of wall thickness were done;the experimental resultshows that wall thickness has a clear influence on the focused gain and the frequency responsefor the focuse     

混合液声速的温度特性

本文考虑到绝热压缩系数与温度的关系,导出了混合液声速与温度、液体比例的关系式。测量了由两种挥发速度不同的液体组成的混合液的声速与温度、液体比例的关系。结果表明,由于挥发速度不同,给测量结果带来较大误差。本文结果除对充液聚焦球内液体选择和配制有重要意义外,也适用于其它各种混合液。     

充液球的聚焦增益及其频率特性与脉宽壳厚的关系

充液聚焦球形反射体(简称充液球)是一种理想的标准反射体。它有几何尺寸小、目标强度大、频率特性好、方向性均匀、成本低、海上布设方便等优点。常用于水声学测量和水声设备的检验,校准及有关人员训练之用。在文献中研究了充液球的目标强度,聚焦增益与频率、方位、折射率的关系,着重研究在温度变化的情况下提高聚焦增益的问题。国外对充液球的目标强度作过研究,但这些工作都是在短脉冲情况下做的。而实际工作中常常使用长脉冲,因此仅有短脉冲结果是很不够的,所以本文着重研究了长脉冲情况下的聚焦增益及其频率特性。