Traditional converging horns, however, despite being widely used in the field of ultrasonics, are incapable of providing any significant amount of total acoustic power, since the amplitude of the output vibrations of such horn directly depends on the reduction of its cross-section towards the output end.  At high gain factors, the output area becomes very small, which complicates using these horns in sonochemical reactors for processing substantial volumes of liquids.  

To increase the radiating surface and try to alleviate this problem, a converging horn can be provided with a section in the form of a thin disk or plate with a larger diameter (usually close to the horn input diameter) at its output end.  Sometimes a short transition section of arbitrary shape is also placed between the horn and the plate at its output end.  These horn designs have substantial disadvantages.  First, when the ratio of the length to the diameter of any horn element is about 0.5, the vibrations that take place in the horn become very complex.  Instead of the axial (longitudinal) mode of vibrations, which must occur in the body of the horn, other non-axial vibration modes appear (for example, flexural vibrations).

This leads to a disruption of the regime of the operation of the entire horn.  Its natural resonance frequency changes and, as a consequence, additional experimental fitting of geometrical dimensions is required.  This manifests itself particularly clearly at high vibration amplitudes of the specified section of the horn.  Second, the length of the specified exit section is small as compared with its diameter and, therefore, in this section the degree of strain (and, as a consequence, stress) along the section length is high, which substantially decreases the operational life span of such a horn.

At Industrial Sonomechanics LLC, we have developed a completely novel principle of designing acoustic horns, which, as a result, combine in themselves the capabilities to provide high gain factors and large radiating output surfaces simultaneously.  These horns, composed of five elements, are called “barbell horns”.

Figure 3 shows the schematic of such barbell horn with a catenoidal transitional element.  Plots of the vibration amplitude distribution and the deformation along the horn’s length are also given.  Here: V(z) – amplitude of vibration velocity; e(z) – deformation amplitude; k – wave number; Ln – vibration node position; L – vibration antinode position;  L1, L2, L3, L4, L5 – corresponding element lengths; D0, D1, D2 – cross-section diameters.

FIGURE 3

Figure 4 gives a better idea on what this horn looks like in real life.

FIGURE 4