In a church, speech intelligibility is a very important condition together with the reverberance for musical activities. In order to realize these two incompatible conditions, public address (P. A.) systems are often used to improve speech intelligibility. In the acoustical design of St. Ignatius Church in Tokyo, a 1/20-scale model experiment is being made, in which the acoustic conditions, including the effect of the P.A. system, are investigated by applying the hybrid simulation technique. As for the sound sources to measure impulse responses, four types of spark-discharge impulse sources---a simple omnidirectional one and three directional ones which simulate human heads and two types of horn-type loudspeakers---have been developed. In order to investigate the effect of the P. A. system, impulse responses measured under various configurations are convolved with dry sources (speech and music) and judged by means of a subjective hearing test.