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This paper presents an equivalent fluid model (EFM) formulation in a three-dimensional time-domain discontinuous Galerkin finite element method framework for room acoustic simulations. Using the EFM allows for the modeling of the extended-reaction (ER) behavior of porous sound absorbers. The EFM is formulated in the numerical framework by using the method of auxiliary differential equations to account for the frequency dependent dissipation of the porous material. The formulation is validated analytically and an excellent agreement with the theory is found. Experimental validation for a single reflection case is also conducted, and it is shown that using the EFM improves the simulation accuracy when modeling a porous material backed by an air cavity as compared to using the localreaction (LR) approximation. Last, a comparative study of different rooms with different porous absorbers is presented, using different boundary modeling techniques, namely, a LR approximation, a field-incidence (FI) approximation, or modeling the full ER behavior with the EFM. It is shown that using a LR or FI approximation leads to large and perceptually noticeable errors in simulated room acoustic parameters. The average T 20 reverberation time error is 4.3 times the just-noticeable-difference (JND) threshold when using LR and 2.9 JND when using FI.

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This paper presents an investigation into the perceptual vibrotactile thresholds for a range of frequencies on both the inside and outside areas of the wrist when exciting the skin with parallel vibrations, realized using the L5 actuator made by Lofelt GmbH. The vibrotactile threshold of 30 participants was measured using a modified audiometry test for the frequency range of 25 - 1000 Hz. The average threshold across the respective frequencies was then ultimately determined from acceleration minima. The results show that maximum sensitivity lies in the range of 100 - 275 Hz (peaking at 200 Hz) for the inside and 75 - 250 Hz (peaking at 125 Hz) for the outside of the wrist and that thresholds are overall higher for the hairy skin on the outside of the wrist than for the glabrous skin on the inside. The results also show that the vibrotactile thresholds varied highly between individuals. Hence, personalized threshold measurements at the actuator locations will be required in order to fine tune a device for the user. This study is a part of an on-going research and development project where the aim is to develop a tactile display device and a music encoding scheme with the purpose of augmenting the musical enjoyment of cochlear implant recipients. These results, along with results from planned follow-up experiments, will be used to determine the appropriate frequency range and to cast light on the dynamic range on offer for the tactile device.

The use of model-based numerical simulations of wave propagation in rooms for engineering applications requires that acoustic conditions for multiple parameters are evaluated iteratively, which is computationally expensive. We present a reduced basis method (RBM) to achieve a computational cost reduction relative to a traditional full-order model (FOM) for wave-based room acoustic simulations with parametrized boundaries. The FOM solver is based on the spectral-element method; however, other numerical methods could be applied. The RBM reduces the computational burden by solving the problem in a low-dimensional subspace for parametrized frequency-independent and frequency-dependent boundary conditions. The problem is formulated in the Laplace domain, which ensures the stability of the reduced-order model (ROM). We study the potential of the proposed RBM in terms of computational efficiency, accuracy, and storage requirements, and we show that the RBM leads to 100-fold speedups for a two-dimensional case and 1000-fold speedups for a three-dimensional case with an upper frequency of 2 and 1 kHz, respectively. While the FOM simulations needed to construct the ROM are expensive, we demonstrate that the ROM has the potential of being 3 orders of magnitude faster than the FOM when four different boundary conditions are simulated per room surface.