In augmented reality applications, where room geometries and material properties are not readily available, it is desirable to get a representation of the sound field in a room from a limited set of available room impulse response measurements. In this paper, we propose a novel method for 2D interpolation of room modes from a sparse set of RIR measurements that are non-uniformly sampled within a space. We first obtain the mode parameters of a measured room. Using the commonacoustical pole theory, the mode frequencies and decay rates are kept constant over space, and a unique set of mode amplitudes is obtained for each measurement location. Based on the general solution to the Helmholtz equation, these mode amplitudes are modeled as periodic functions of 2D spatial location. For low frequency room modes, the model parameters are found with sequential non-linear least squares. Results show accurate spatial interpolation of perceptually relevant low frequency modes in rooms with simple geometries having non-rigid walls.
The Indian classical music system follows a cyclic perception as against the linear approach of reductionist concept in Western music. In every tāla, there exists a pattern of tangible and intangible events that keeps on repeating in smaller cycles. If such repeating pattern is detected, it will be an important step in the context of rhythm analysis of hindustani music and also for rhythm-based retrieval. In this work, a simple but novel methodology is presented to detect two important rhythmic aspects of tāla namely, tempo and mātrā. It is focussed on the detection of the repeating structure by analysing the tablā signal. The work extends our earlier effort that deals with only the electronic tablā signal which is well behaved. In this work, pitfalls of the earlier methodology are analysed and corrective measures are adopted to formulate the improved methodology. The present work computes and tunes the parameters based on the signal content and can work with the signals of wide variety, including the not so well-behaved real tablā signal, i.e. the signal captured when tablā is played by human artist. Experiment is carried out with a large number of electronic and real tablā clips reflecting variety of tempo and tāla. Performance of B Sanjoy Kumar Saha the proposed methodology is also compared with that of the earlier one. Result indicates the superiority and effectiveness of the proposed methodology.
Feedback Delay Networks are one of the most popular and efficient means of generating artificial reverberation. Recently, we proposed the Grouped Feedback Delay Network (GFDN), which couples multiple FDNs while maintaining system stability. The GFDN can be used to model reverberation in coupled spaces that exhibit multi-stage decay. The block feedback matrix determines the inter-and intra-group coupling. In this article, we expand on the design of the block feedback matrix to include frequencydependent coupling among the various FDN groups. We show how paraunitary feedback matrices can be designed to emulate diffraction at the aperture connecting rooms. Several methods for the construction of nearly paraunitary matrices are investigated. The proposed method supports the efficient rendering of virtual acoustics for complex room topologies in games and XR applications.
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