Acoustical coupling until now has basically been studied to define the peculiar sound field within acoustically coupled enclosures in which multiple-slope energy decays can often be observed. The key concern of this study is to reveal the potential of multiple-slope energy decay formation in over-size single space structures with particular geometry and distribution of materials in different acoustical performance characteristics. Specifically, multiple dome superstructures, composed of one central dome supported by semi-domes and transitional elements, are selected for the case studies. The interpretation of the acquired data is carried in order to broaden the definition of “the coupled volume system” with an emphasis on invisible sources and apertures of acoustical coupling in a “single volume system.” The methodology of the research involves joint use of in-situ acoustical measurements, acoustical modeling/simulation methods, and computational analyses. Bayesian analysis approach is applied in quantifying multiple-slope decay parameters. Initial results for selected cases indicate double and triple slopes for field tests and even more slope natures for simulations at various frequency bands. Future work aims to elaborate the mechanism of multiple-slope decay occurrence by energy feedback and distribution analysis.