<div class="htmlview paragraph">This paper describes an attempt to clarify the characteristics of combustion noise generation of the engine structure. The transmission-radiation coefficient of combustion noise is proposed as a conversion ratio of the combustion noise power from the gas vibration power affecting the inner surface of the combustion chamber These experiments were carried out both with a stationary engine excited by a single explosion and an operating engine. From these results, the frequency characteristics of the combustion noise generated by each engine wall and the vibration response of each transmission path are discussed.</div>