The present invention provides a sound pressure signal output apparatus capable of synthesizing and outputting a sound pressure signal that simulates the sound of a real engine with reduced processing load in real time while flexibly adapting to specification changes. The sound pressure signal output apparatus comprises: an interface that acquires single sound data corresponding to the sound generated by one cylinder of a vehicle-mounted internal combustion engine during one combustion cycle in the cylinder, acquires order sound data corresponding to order sound for a frequency corresponding to the engine rotation speed, and acquires random sound data generated corresponding to at least either the material or the shape of the structure that makes up an engine; and a synthesis unit that synthesizes and outputs the sound pressure signal of an engine sound using the single sound data and the like acquired.