Abstract: A sonic or ultrasonic apparatus for exposing sheet material having a heat fusible component disposed therein to high frequency vibrational or mechanical energy to perform an operation thereon. The apparatus includes a plurality of electro-acoustical converter units, each of which is energized by high frequency electrical energy that is converted into high frequency vibrational energy. The units are horizontally spaced in juxtaposition to each other in line transversely above the sheet material, and each electro-acoustical converter unit has a horn resonant at the high frequency vibrational energy which opposes stationary anvil means positioned beneath the sheet material.