Today, due to the importance of emulsions in various industries, it is important to know the methods and tools available to create a stable emulsion. Common emulsification tools are available in laboratories and the food industries. Research has shown that to create a relatively stable oil-in-water emulsion, the ultrasonic method has many advantages in terms of energy efficiency, reduced emulsion particle size, better emulsifying quality, wider application and range, and greater ease of operation than other methods. This new and efficient method is widely used to destroy the molecular structure of materials and improve homogenization operations. The horn is one of the most important components in the ultrasonic system, which is responsible for transmitting vibrations and amplifying the amplitude produced by the transducer. According to research, the contact surface of the horn with the fluid and the amplification of the vibration amplitude by the horn are both factors that in the homogenization process cause the shredding and reduction of fat particle size, resulting in a relatively stable emulsion. Therefore, in the present research, we have tried to design the horn in such a way that the factors of the contact surface and amplification of vibration amplitude are in the optimal state. The design was first done analytically and then evaluated by numerical solution, which resulted in the design and construction of a multi-step barbell horn with a gain factor of 15. Finally, the performance of the designed horn was compared with the food industry laboratory horn at two, three and four minutes of sonication in three replications. Therefore, factorial experiment and completely randomized design consisting of 6 treatments with three replications were used. To prove the relative stability of the resulting emulsion, the properties of the creaming index, emulsion activity index and emulsion stability index were measured, which resulted in a more stable oil-in-water emulsion sonicated by a horn designed in 4 minutes. Key Words: Multi-step barbell horn, Gain Factor, Creaming index, Activity index, Stability index
