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Developments in Ceramic Materials Research

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150<br />

Dimitris Skarlatos, Tilemachos Zak<strong>in</strong>th<strong>in</strong>os and Ioanis Koumanoudis<br />

Figure 8. Wall <strong>in</strong> positions of sound vessels.<br />

The perforat<strong>in</strong>g seems to have been made before the wall<strong>in</strong>g-<strong>in</strong>. In cyl<strong>in</strong>drical or<br />

spherical surfaces, the axis of the vase is arranged <strong>in</strong> the same direction of the radius of the<br />

cyl<strong>in</strong>der or of the sphere of the wall surface. An exception is observed when the vase is<br />

placed with its ma<strong>in</strong> axis fac<strong>in</strong>g upwards, <strong>in</strong> which case a hole is opened at the side of its<br />

volume. One might ask why this arrangement. At this po<strong>in</strong>t it is important to stress that the<br />

shape of the aperture of the sound vessel affects its acoustical performance.<br />

In Europe some of the vases with large mouths were often reduced <strong>in</strong> aperture by be<strong>in</strong>g<br />

placed beh<strong>in</strong>d perforated stone or wooden screens or partly plugged with a wooden block<br />

(e.g. Denford Northamptonshire, St Mary-le-Tower Ipswich) [27, 16]. Accord<strong>in</strong>g to Bruel <strong>in</strong><br />

some cases <strong>in</strong> Scand<strong>in</strong>avian churches, additional frictional resistance was provided by

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