Researchers developed an ultrasonic espresso process that uses high-frequency sound waves instead of hot water to produce espresso-strength coffee at room temperature. And, not only did coffee drinkers find it comparable to traditional espresso, but the brewing process cut energy use by up to 75%. An anonymous reader quotes a report from The Conversation: We have developed what we call an ultrasonic espresso: a room-temperature brewing process that uses high-frequency sound waves to extract the flavor, oils, aroma and caffeine from coffee grounds.