43O升充水圆柱形声共振器的研究

为了在实验室内用共振法测量海水低频声吸收及研究海水低频弛豫吸收的机理(海水中的硼弛豫其弛豫频率约为1千赫),关键是需要一个容量大而附加损失小的声共振器。     

海水中硼酸弛豫声吸收机理的研究

通过共振器法测量获得了硼酸弛豫的弛豫频率和最大波长吸收与硼酸及碳酸氢钠浓度的依赖关系.实验结果可以用一个表观的一步反应:B(OH)_3+CO~2-_3(总)+H_2O(?)B(OH)~-_4(总)+HCO~-_3(总)来解释。本文的理论和实验表明可以用与此表观反应等价的耦合反应系统(包含所有的离子缔合反应)来解释Ca对硼酸弛豫参数的影响。     

INVESTIGATION OF THE MECHANISM OF SOUND ABSORPTION BY THE BORIC ACID RELAXATION IN SEA WATER

The dependencies of the relaxation frequency and the maximum absorption per wavelength ofboric acid relaxation on B(OH)_3 and NaHCO_3 concentrations were obtained by the cylindrical resona-tor method.The experimental results may be explained by an apparent one-step process:Theory and experimental results show that the effects of calcium on the relaxation parameters of boricacid relaxation can be interpreted by a coupled-reaction system,which is equivalent to that apparentone-step process,including all the ion association reactions.     

海水的低频化学弛豫声吸收

用圆柱共振器法测量了三种混合水溶液的声吸收与pH值的依赖关系,溶液中每种化学成分的浓度均参照Lyman-Fleming人造海水配方中对应成分的浓度来选取。测量的频率为2.9和6.8kHz。温度为12.4℃。结果表明,在海水的pH值范围内,B(OH)_3弛豫的弛豫频率与pH值没有明显依赖关系。另外由实验结果可以看出在B(OH)_3/CO_2/Ca/Mg/NaCl水溶液中还存在一个由MgHCO~+_3引起的低频弛豫,其弛频约为3.5kHz。文末列出了由本文测得的B(OH)_3,MgCO_3和MgHCO~+_3弛豫的弛豫参数。     

SOUND ABSORPTION IN SEA WATER DUE TO LOW FREQUENCY CHEMICAL RELAXATIONS

The dependencies of sound absorption on pH value of B(OH)_3/CO_2/Ca/NaCl,B(OH)_3/CO_2/Ca/Mg/NaCl and Mg/CO_2/Ca/NaCl systems are measured at 2.9 and 6.8 kHz by the cylindrical resonatormethod.The concentration of each constituent in these systems is the same as that in Lymanand Fleming sea water.Measurements are made at atmospheric pressure and 12.4℃.Results showthat the relaxation frequency of B(OH)_3 is independent of the pH value in the seawater.It seemsclear that there is another low frequency relaxation caused by MgHCO_3~+(f_r～3.5 kHz)in theB(OH)_3/CO_2/Ca/Mg/NaCl system.The relaxation parameters of the B(OH)_3,MgCO_3 and MgHC0_3~+relaxations for various systems are given.     

MEASUREMENTS OF THE pH DEPENDENCE OF LOW FREOUENCY SOUND ABSORPTION IN SEA WATER

The dependence of sound absorption coefficient in natural sea water on pH at frequencies of 2.91,6.82and 10.76 kHz has been measured by the resonator method.Measure-ments were made at 12.6℃ in the pHrange 6.48—8.51.Comparison of the experimental results with predictions based on various equations isgiven.One of the principal objectives in this paper is to examine the contribution of the MgSO_4 absorption insea water by reducing pH to low enough values where the pH-dependent absorption losses become negligible.It seems clear that in order to predict sound absorption in sea water more accurately at both low and highfrequency ranges with an united equation,the equation should include the MgHCO_3~+ absorption term as wellas the MgCO_3 term.     

海水低频声吸收与pH值的关系

本文用共振器法测量了天然海水低频声吸收与pH值的关系。测量频率为2.91、6.82和10.76kHz;pH值范围为6.48—8.51;温度为12.6℃。测量结果与不同的声吸收公式计算值进行了比较。本文实验的主要目的之一是通过将pH值减小到足够小的数值来检验海水中MgSO_4吸收的贡献。实验结果表明:为了能用一个统一的公式较准确地预估低频和高频的海水声吸收,此公式看来应该既包括MgCO_3吸收项,又包括MgHCO_3~ 吸收项。     

STUDY OF THE 430-LITER WATER-FILLED CYLINDRICAL ACOUSTICAL RESONATOR

A cylindrical aluminum vessel with an inside diameter of 100 cm and a height of 55 cm is used.Radiation through the air is minimized by appropriately selecting the distances from the resonatorsurface to the outer cylindrical steel chamber and the additional reflecting surfaces.Therefore measure-ments can be made at atmospheric pressure.The lowest decay rates obtained at approximately 3 and7 kHz are 0.15 dB/s and 0.30 dB/s,respectively.