Ultrasonic Horn by Sharpertek. Ultrasonic welding Horn Round shape size: 4inch. Material aluminum with either Chrome or Anodized coating options. Ultrasonic horn frequency is 20KHZ. Part Number: 20KHZ-20KHZ-AL. Sharpertek Ultrasonic Horns are designed and made in Pontiac MI. Finite Element Analysys FEA is used in the engineering of every horn we make to ensure low stresses, proper model shapes, repeatability and durability.