Articles to be cleaned are immersed in a bath subjected to ultrasonic energy emanating from ultrasonic transducers coupled to a vibratory diaphragm contiguous with the bath. The ultrasonic transducers are in multiple sets for providing ultrasonic energy at multiple ultrasonic frequencies at interspersed locations spaced apart a distance e.g. of 3.25 inches. The multiple sets of transducers simultaneously transmit ultrasonic energy at multiple ultrasonic frequencies to the bath. Two ultrasonic frequencies are produced, with the first being about 80 kHz and the second being about 40 kHz.
