<P> Domes with pendentives can be divided into two kinds: simple and compound . In the case of the simple dome, the pendentives are part of the same sphere as the dome itself; however, such domes are rare . In the case of the more common compound dome, the pendentives are part of the surface of a larger sphere below that of the dome itself and form a circular base for either the dome or a drum section . </P> <P> Because domes are concave from below, they can reflect sound and create echoes . A dome may have a "whispering gallery" at its base that at certain places transmits distinct sound to other distant places in the gallery . The half - domes over the apses of Byzantine churches helped to project the chants of the clergy . Although this can complement music, it may make speech less intelligible, leading Francesco Giorgi in 1535 to recommend vaulted ceilings for the choir areas of a church, but a flat ceiling filled with as many coffers as possible for where preaching would occur . </P> <P> Cavities in the form of jars built into the inner surface of a dome may serve to compensate for this interference by diffusing sound in all directions, eliminating echoes while creating a "divine effect in the atmosphere of worship ." This technique was written about by Vitruvius in his Ten Books on Architecture, which describes bronze and earthenware resonators . The material, shape, contents, and placement of these cavity resonators determine the effect they have: reinforcing certain frequencies or absorbing them . </P> <P> The earliest domes in the Middle East were built with mud - brick and, eventually, with baked brick and stone . Domes of wood allowed for wide spans due to the relatively light and flexible nature of the material and were the normal method for domed churches by the 7th century, although most domes were built with the other less flexible materials . Wooden domes were protected from the weather by roofing, such as copper or lead sheeting . Domes of cut stone were more expensive and never as large, and timber was used for large spans where brick was unavailable . </P>

Who is credited with perfecting the arch and the dome