A type of synthetic reverberation system. Plate reverbs were one of the first types of artificial reverbs used in recording. They used a steel plate under tension supplied by springs at the corners where the plate was attached to an outer shell. The plate gets vibrated in accordance with a signal from a transducer and the vibration is sensed elsewhere on the plate with a contact microphone of one type or another. Put your ear up to any large metal item and tap on it and you will hear how steel plates were used to create reverb. Plates were initially used a great deal in the early days of studio recording (even though they don’t sound that much like natural reverberation) due to their relatively small size and low cost when compared to a reverberation room. While many other types of artificial reverbs appeared on the scene (spring, etc.) the plate reined king until the advent of digital reverbs. While in many cases early digital reverbs sounded even less like natural reverb than plates did, they did offer the function at a much lower price and in a much smaller package. Ultimately digital reverbs prevailed sonically as well, and even began to include plate simulations in their algorithms. Of course there are many engineers who still prefer the sound of a good old plate, just like they like other types of vintage equipment.