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Ultrasonic cell or sample holder structure is important for the study of ultrasonic attenuation and velocity of liquids. Intermolecular properties, chemical phenomenon, reaction, thermo-acoustic parameter and physical properties of materials affect the attenuation and velocity of liquids. In this article, we discuss the effects of the ultrasonic cell on ultrasonic attenuation and velocity measurement in liquids. Generally, there are two type of the ultrasonic cell arrangement that are used; double transducer and single transducer. Among these, single transducer approach is widely used because of its inherent advantages. The sample holders are generally fixed transducer type with movable reflector. Ultrasonic attenuation measurement is widely effected by the reflector positioning accuracy, reflector movements, and internal wall structure of ultrasonic cell. Diffraction effects, non-parallelism, phase and imperfect reflection from liquid-reflector interface contributes in errors in the attenuation measurement. The transducer transmission and receiving conversion efficiency also effect the attenuation measurement. The sensitivity of measurement in liquids is mainly influenced by geometrical parameter of the cell. The small change in acoustic path does not affect much attenuation measurement but increases error in the velocity. Ultrasonic velocity may be affected by the error in the reflector transducer separation. The transducer disc diameter, vibration modes and the disc frequency decides the pressure distribution inside the liquid cell. The ultrasonic beam within near field is non-uniform. This causes fluctuation in near field attenuation measurement. The beam divergence in far field play important role for attenuation. The total attenuation consists of loss in liquids and additional losses from beam divergence, scattering from the sidewalls, friction effects and coupling effects. In this article, we also describe the critical issues at near field and far field that contribute significant role for attenuation measurement. The difference in attenuation values measured in far and near field is explained. Effects of each parameter are addressed separately. Finally, it was concluded that the attenuation and velocity measurement ultrasonic cell structure must be considered for better measurement of attenuation and velocity. The attenuation measured at relatively lower frequencies and small transducer diameter gives better results. Also measurements must be carried out preferably in far field.
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