A framework for diffuseness evaluation using a tight-frame microphone-array configuration

This study extends the theoretical framework of diffuseness estimation to practical microphone arrays with different spatial configurations. Building upon the covariance-based model, we formulate a velocity-only covariance framework that enables consistent diffuseness evaluation across heterogeneous array geometries without requiring mode whitening or spherical-harmonic decomposition. Three types of arrays-the A-format, rigid-sphere, and a newly proposed tight-frame array-are modeled and compared through both simulation and measurement experiments. The results demonstrate that the proposed tight-frame configuration achieves isotropic sampling and reproduces diffuseness characteristics equivalent to those of higher-order spherical arrays, while maintaining a compact physical structure. We also examine the accuracy of acoustic-intensity detection within the same framework. The findings bridge theoretical diffuseness analysis and practical implementations, contributing to the design of robust sound-field measurement systems.