Measurement, visualization, and modeling of acoustics of a barrel-vaulted sanctuary

Abstract

This investigation centers on a recently constructed church with a barrel-vaulted sanctuary ceiling (13.1 m x 12.7 m x 6.0 m) exhibiting excessive reverberation times. An acoustical engineer consulted during design recommended that the original arched ceiling be replaced with a series of flat surfaces constructed to create a similar visual appearance without causing focused echoes. However, due to miscommunication, these recommendations were not incorporated into the construction of the building. Based on complaints of poor speech intelligibility at specific locations, an investigation was made consisting of reverberation time measurements developed from logarithmic sine sweep data and sound pressure level measurements in the diffuse sound field. Reverberation times in excess of 5 seconds in the speech-frequency range were observed at locations along the center aisle, along with correspondingly elevated sound pressure levels. A CAD model of the sanctuary was developed, imported into Odeon and used to simulate the acoustical behavior. Multiple means for visualizing the acoustical behavior are presented, demonstrating how the long reverberation time can be detected in the measured data as well as the models. Odeon analysis of proposed solutions for retrofit of the space to improve intelligibility are also described.