Wash Dishes Ultrasonically. High frequency sound waves energize the water to wash the dishes in this ultrasonic dishwasher. A device called a transducer produces the high frequency sound waves (about 20,000 cycles per minute), pitched so high they cannot be heard by the human ear. Ultrasonic washers are more effective than existing types; they scour without scratching, remove baked-on matter readily, and wash much faster than any type now in general use. The same principle of ultrasonic cleaning will be applied to washing machines within another decade.
from 1975: And the Changes To Come by Arnold B. Barach