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sound-reflecting wall, floor and ceiling surfaces. This pro- vides a greater increase in the loudness at the listener’s ears between the direct sound from the speaker and loudspeak- ers relative to the loudness of reverberant sound in the room. As this technology improves, it becomes possible to suspend a smaller number of speakers over the perfor- mance platform to enhance the intelligibility of the spoken word to larger congregations.
One recent example of the successful use of steered arrays is the United Methodist Church of the Resurrection in Leawood, Kansas (Figure 5). The loudspeakers allow a great deal of directivity pattern flexibility. As a result, the sound energy emanating from them covers the wide wraparound seating area, with minimal sound spill onto reflective surfaces such as the walls outside the seating area, the platform, and the ceiling.
Natural Enhancement of Speech Intelligibility
The acoustical design of modern Jewish Orthodox syna- gogues is one unique challenge that deserves its own discussion. One challenge is that some of these spaces are quite large; providing good speech intelligibility to hundreds of people for unamplified speaking is a formidable chal- lenge. Keeping background noise levels very low (e.g., from the building’s HVAC systems, outside noise) is one essen- tial design consideration because high speech intelligibility requires a good signal-to-noise ratio. Because the loudness of the signal (unamplified speaking) is limited, with no abil- ity to boost the level with an electronic sound reinforcement system, the “noise” must be as low as possible to increase the signal-to-noise ratio in the worship space.
The room shaping must be designed to reflect the sound of a person speaking into the congregational seating area. The sooner those reflected sounds arrive, the louder they
will be. Also, our auditory system integrates reflected sounds arriving soon after the direct sound more effec- tively than later-arriving reflected sounds to improve speech intelligibility.
An additional complication in an Orthodox synagogue is that there are two different and important locations where speaking or chanting takes place. One is from the center bimah where the speaker faces the front of the room (the Ark) with his back to half the congregation.
The second location is from the Ark facing the congre- gation; the room shaping must support strong early reflections to the entire congregational seating area for both speaking locations.
One example is Young Israel of Greater Cleveland in Beachwood, Ohio. The seating capacity of this Orthodox synagogue is unusually large. Providing excellent speech intelligibility for such a large congregation without the
Figure 6. Reflections for a sound source originating at the central bimah of a synagogue (top) and from the Ark (bottom).
Figure 7. Young Israel of Greater Cleveland Orthodox synagogue in Beachwood, Ohio, features ceiling shaping to support a person speaking at two critical locations.
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