Relationship between room characteristics and speech intelligibility in contemporary churches in Malaysia

Abstract

Church as a place of worship has a unique architectural style and is of great social importance for the Christian community. The church geometric configurations vary from classical cruciform to octagonal-shaped plan. Acoustically, some geometric shapes work much better than others while others can be downright awful. The objective of this study is to investigate the relationship between room characteristics and speech intelligibility in church acoustics. At the first stage of this study, a total of eight existing churches in Malaysia were identified and then grouped into three types, i.e. fan, rectangular, and cruciform. Then, a fan-shaped room model was selected to be simulated in detail for sectional studies. Nine different ceiling shapes were constructed for evaluation purposes. All the selected churches were modelled using the 3D modelling software, SketchUp and then exported into the commercial acoustic software, ODEON, for acoustical simulation. The simulated results were then compared to the parameter of speech transmission index (STI). The results indicate that there was no specific relationship of the STI with all three groups of room types. However, a direct relationship between the STI means value with its room volume as well as its distance between sound source and receiver points can be observed, whereby F3 being the highest average value of STI (0.44) whereas R2 showed the lowest average value of STI (0.30). All room models generally achieved 'fair' STI values at the front position of the altar but the STI values drop into 'poor' when the distance exceeds over than 6.5 m. In the second stage, the results obtained show a direct relationship between the STI means values with the lower ceiling height above the sound source and a shorter distance between the sound source and its surrounding walls that may provide higher speech intelligibility due to the strong early sound energy. This paper provides fundamental data on the relationships between room characteristics and speech intelligibility, which would then help with future refinements.

A Comparison of Acoustical Performance Between Traditional and Modern Church

“…In a confined environment, sound will echo through the room for a period of time even after the origin has ended producing energy [10]. Reverberation time (RT) is defined as the time taken for the sound level to drop by 60dB after the sound source has ceased.…”

“…As time passes, the modern churches comprise several activities based on the congregational style of the church. For instance, the scale of Roman Catholic cathedrals increased, resulting in high reverberant acoustic environments for worship music and chants [10]. However, these cathedrals do have to perform the task of delivering God's message and speeches, which require a greater need for intelligibility of speech.…”

“…It is critical to generate appropriate speech communication that can be clearly understood from any seating arrangement in the church; or else, members will experience isolation. Everyone in the prayer service should be experiencing the same acoustical environment since everyone is considered same in God's temple [10]. Thus, it is a challenge for acoustical design in churches as there needs to be a balance between both good speech intelligibilities in the sermon and instrumental worship [11].…”