Abstract: An engine knock detector including a first mechanism for sensing engine noise during a first time period of an engine combustion cycle and providing a first signal in response thereto. A second mechanism is also provided for sensing engine noise and engine knock during a second time period of the combustion cycle and providing a second signal in response thereto. Finally, a third mechanism is included for comparing the first and second signals and generating a third signal to determine the occurrence of an engine knock. In a preferred embodiment, a vibration signal represented by an electrical voltage is bandpass amplified, digitized and filtered by a tunable filter. The filtered digital signal, which represents engine vibrations, is then directed to first and second energy detectors. The coefficients of the tunable filter and the timing signals of the energy detectors are provided by a programmable memory.