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吴嘉  席葆树  许宏庆 《应用声学》2002,21(3):21-24,17
本文在声频信号下发现驻波管底部的微小颗粒群在一定声场强度下会腾空而起,在管中形成稳定的悬浮层。通过相位多谱勒(PDA)测量发现,只有粒径在一定范围内的颗粒才能稳定悬浮在管中,且颗粒悬浮层中颗粒的粒径按一定的高度规律分布,这一结果在粉尘颗粒分离,分级中有广阔的应用前景。  相似文献
2.
A lateral Helmholtz resonator added to a standing wave tube without flow has been validated as a method of noise reduction for combustion noise radiated from combustion channel of rockets or turbines. But in fact there is a flow with low velocity in the combustion channel. Therefore the theoretical analysis carried out is aimed at sound field of standing wave tube with flow and with lateral Helmholtz resonator. Certainly a relevant math-physical model should first be formulated. Here three key problems need to be solved: (1) To formulate the discontinuity condition at the joint between the standing wave tube and Helmholtz resonator in the case of flow. (2) To determine the acoustic impedance of Helmholtz resonator, considering the effects of flow, viscous and multihole. (3) To formulate the reflection condition at the end of the standing wave tube. Some formulas for analysis of the sound field in the tube with flow and with lateral Helmholtz resonator are deduced. These theoretical works have been validated by experiments.  相似文献
3.
王泽锋  胡永明 《声学学报》2008,33(2):184-191
穿孔板结构在水下有着非常广阔的应用前景,但是目前相关的研究报道非常少.基于空气中穿孔板吸声理论,综合考虑小孔的末端修正,给出了较为准确的水下穿孔板声阻抗表达式.利用传递矩阵法分析了水下穿孔板结构的声压透射特性,得到了垂直入射声压透射公式.对影响穿孔板结构透声性能的主要因素进行了详细的仿真分析,得到了一些重要的结论.采用四传感器测量方法在驻波管中对自制的穿孔板结构进行了测试,实验结果与理论分析基本一致,从而验证了理论分析的正确性.本文为水下穿孔板结构的设计提供了详细的理论和实验依据.  相似文献
4.
闵琦  刘克 《物理学报》2011,60(2):24301-024301
由直径不同的两级直圆管连接而成的两级突变截面驻波管具有失谐性,即高阶共振频率不是一阶共振频率的整数倍. 两级突变截面驻波管的失谐性质能够很好地抑制一阶共振频率激励下的大振幅非线性驻波畸变产生的高次谐波,从而获得大振幅纯净驻波场. 通过对两级突变截面驻波管失谐性质的研究,采用大功率扬声器正接等措施,利用两级突变截面驻波管的失谐性质在一阶共振频率激励下获得了184 dB的极高纯净驻波场,并对二至五阶共振频率激励下的声场进行了相应的实验研究. 在二阶、四阶共振频率激励下分别获得了180和166 dB波形比较规整的大振幅非线性驻波,并在三阶、五阶共振频率激励下观察到了谐波饱和现象和锯齿波. 关键词: 失谐驻波管 大振幅驻波 畸变 饱和  相似文献
5.
A standing-wave tube with tapered section(STTS) was evolved from a standing-wave tube with abrupt section(STAS) whose abrupt section was replaced with tapered section. The research was intended to compare the acoustic properties and the extremely nonlinear pure standing waves of STTS with those of STAS.The acoustic properties of the STTS were studied with transfer matrix.It was proved,like the STAS,that the STTS was dissonant standing-wave tube.With its dissonant property,the 181 dB extremely nonlinear pure standing wave was obtained in the STTS excited at its first resonance frequency.Then the comparative experimental studies on the saturation properties of the extremely nonlinear standing waves were carried out in the STTS and the STAS with the same length.It was found that the STTS could suppress the harmonics and meanwhile reduce energy loss of the standing wave more effectively.Compared with the STAS,under the same voltage of loudspeaker,the STTS obtained a higher extremely nonlinear pure standing wave.Moreover,it was found for the STTS that the third harmonic of the third resonance frequency was close to the seventh resonance frequency of sound source impedance,to which the valley value of the sound pressure level transfer function corresponded.Because of this,the third harmonic increased rapidly with the increase of fundamental wave and tended to saturate.  相似文献
6.
Standing-wave tube with abrupt section (STAS) was a dissonant standing-wave tube whose higher resonance frequencies were not integral multiplies of the first one. Making use of the dissonant property of STAS and through the optimization of the system, extremely nonlinear pure standing-wave field of 180 dB at the first resonance frequency and that of 177 dB at the second resonance frequency have been obtained. At the two resonance frequencies, distortion of waveform and saturation of harmonics were studied experimentally, but saturation did not appear even though under such high sound pressure levels. However, while nonlinear sound field was experimentally studied at the third resonance frequency, it was found that the frequency for the second harmonic of the third resonance frequency was close to the sixth resonance frequency of the STAS and the distortion of waveform and the saturation of harmonies appeared as the sound pressure level approached 170 dB.  相似文献
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