Diesel Sound Generator For Model Boats

64 EE March 1989 DIESEL SOUND GENERATOR FOR MODEL BOATS A low-cost circuit that imitates the sound of a high-power, 10 to 20-cylinder, diesel engine in medium-sized vessels used in, for in- stance, coastguard and fire brigade services. To obtain a realistic effect in model boats, the design is complete with a powerful AF amplifier, and changes the generated sound both in frequency and character as a function of engine speed. The basic sound of an idling diesel engine as used in medium-size marine craft is a low-frequency hum with a slow beat-like interference that is periodically inaudible owing to the hissing sound produced by the exhaust system. As the engine runs faster, the frequency of the basic sound rises, and is less affected by other sounds. Sound of an idling engine The circuit diagram of Fig. 1 shows that the sound generator is built around three square-wave generators. Two of these provide the actual idling sound, the third the effects related to increased speed. The i...