Microphone are provided to an intake port of an engine and a wall surface of an engine room on the interior side respectively to collect an engine sound. The engine sound is processed by a signal processing portion and output via a speaker provided to an interior of a vehicle. Filters for simulating the noise insulating characteristic in the interior of the vehicle and filters for processing the engine sound to emphasize the driving conditions are provided to the signal processing portion. Filter characteristics of the filters are decided in response to sensed values of an engine revolution sensor 30, an accelerator opening angle sensor, and a speed sensor. The driving conditions are emphasized by filtering the engine sound based on the filter characteristics.