Browsing by Department "KU Leuven"

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  • Benchmarking of finite-difference time-domain method and fast multipole boundary element method for room acoustics
    (2022-03-30) Li, Yue; Meyer, Julie; Lokki, Tapio; Cuenca, Jacques; Atak, Onur; Desmet, Wim
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Compared to geometrical acoustics, wave-based methods which solve the wave equation either in the time domain or in the frequency domain are known for their high accuracy. However, their systematic use as professional room acoustic simulation tools is less popular due to the modelling effort and computational time requirements, especially in the case of complex scenarios. This paper aims at providing guidelines for the use of two wave-based methods in complex room acoustics simulations, namely the finite-difference time-domain (FDTD) method and the fast multipole boundary element method (FMBEM). Numerical experiments are conducted to address the convergence issues of the two solvers, more specifically, the selection of the convergence tolerance of the iterative solver in FMBEM and the temporal sampling frequency in FDTD. To evaluate the capability of the solvers in simulating complex scenarios, five cases with increasing complexity of material input data are presented. The results show that both solvers give close predictions for various room acoustics parameters. In addition, an uncertainty sensitivity study is performed in a case where experimental data is available. Large deviations between measured and simulated reverberation time reveal that typical material data-sets poorly represent the behaviour of real materials in a room acoustics context. Lastly, the efficiency of the two solvers is discussed. With parallelization implemented, both solvers can simulate sizeable room acoustic problems with good accuracy within a reasonable time.
  • Multi-Source Direction-of-Arrival Estimation using Group-Sparse Fitting of Steered Response Power Maps
    (2023) Tengan, Elisa; Dietzen, Thomas; Elvander, Filip; Van Waterschoot, Toon
     Conference article in proceedings
    In this paper, a method is proposed for estimating the direction of arrival (DOA) of multiple broadband sound sources by solving a group-sparse optimization problem. A steered response power (SRP) map is modeled using power spectral densities (PSDs) defined on an overcomplete grid of candidate DOAs. The source DOAs are then estimated as the directions corresponding to the largest peaks of the frequency-averaged PSDs. The proposed optimization problem is iteratively solved using the alternating direction method of multipliers (ADMM), and simulation results show that the proposed method overall outperforms the frequency-domain sparse iterative covariance-based estimation (SPICE) method and performs better than or similar to the conventional SRP-PHAT method for varying levels of noise and reverberation.
  • Publicly Verifiable Zero-Knowledge and Post-Quantum Signatures from VOLE-in-the-Head
    (2023) Baum, Carsten; Braun, Lennart; de Saint Guilhem, Cyprien Delpech; Klooß, Michael; Orsini, Emmanuela; Roy, Lawrence; Scholl, Peter
     Conference article in proceedings
    We present a new method for transforming zero-knowledge protocols in the designated verifier setting into public-coin protocols, which can be made non-interactive and publicly verifiable. Our transformation applies to a large class of ZK protocols based on oblivious transfer. In particular, we show that it can be applied to recent, fast protocols based on vector oblivious linear evaluation (VOLE), with a technique we call VOLE-in-the-head, upgrading these protocols to support public verifiability. Our resulting ZK protocols have linear proof size, and are simpler, smaller and faster than related approaches based on MPC-in-the-head. To build VOLE-in-the-head while supporting both binary circuits and large finite fields, we develop several new technical tools. One of these is a new proof of security for the SoftSpokenOT protocol (Crypto 2022), which generalizes it to produce certain types of VOLE correlations over large fields. Secondly, we present a new ZK protocol that is tailored to take advantage of this form of VOLE, which leads to a publicly verifiable VOLE-in-the-head protocol with only 2x more communication than the best, designated-verifier VOLE-based protocols. We analyze the soundness of our approach when made non-interactive using the Fiat-Shamir transform, using round-by-round soundness. As an application of the resulting NIZK, we present FAEST, a post-quantum signature scheme based on AES. FAEST is the first AES-based signature scheme to be smaller than SPHINCS+, with signature sizes between 5.6 and 6.6kB at the 128-bit security level. Compared with the smallest version of SPHINCS+ (7.9kB), FAEST verification is slower, but the signing times are between 8x and 40x faster.