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A common aim in virtual reality room acoustics simulation is accurate listener position dependent rendering. However, it is unclear whether a mismatch between the acoustics and visual representation of a room influences the experience or is even noticeable. Here, we ask if listeners without any special experience in echolocation are able to identify their position in a room based on the acoustics alone. In a first test, direct comparison between acoustic recordings from the different positions in the room revealed clearly audible differences, which subjects described with various acoustic attributes. The design of the subsequent experiment allows participants to move around and explore the sound within different zones in this room while switching between visual renderings of the zones in a head-mounted display. The results show that identification was only possible in some special cases. In about 74% of all trials, listeners were not able to determine where they were in the room. The results imply that audible position dependent room acoustic rendering in virtual reality may not be noticeable under certain conditions, which highlights the importance of evaluation paradigm choice when assessing virtual acoustics.

Funding Information: This research is part of the activities of the Nordic Sound and Music Computing Network— NordicSMC (NordForsk project no. 86892) and has received funding from the European Union Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 812719. Funding Information: This research is part of the activities of the Nordic Sound and Music Computing Network- NordicSMC (NordForsk project no. 86892) and has received funding from the European Union Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 812719. Publisher Copyright: Copyright: © 2022 Jon Fagerström et al. This paper proposes dark velvet noise (DVN) as an extension of the original velvet noise with a lowpass spectrum. The lowpass spectrum is achieved by allowing each pulse in the sparse sequence to have a randomized pulse width. The cutoff frequency is controlled by the density of the sequence. The modulated pulse-width can be implemented efficiently utilizing a discrete set of recursive running-sum filters, one for each unique pulse width. DVN may be used in reverberation algorithms. Typical room reverberation has a frequency-dependent decay, where the high frequencies decay faster than the low ones. A similar effect is achieved by lowering the density and increasing the pulse-width of DVN in time, thereby making the DVN suitable for artificial reverberation.

Multichannel auralizations based on spatial room impulse responses often employ sample-wise assignment of an omnidirectional response to form loudspeaker responses. This leads to sparse impulse responses in each reproduction loudspeaker and the auralization of transient signals can sound rough. Based on this observation, we conducted a listening test to examine the general phenomenon of roughness due to spatial assignment. First, participants assessed the roughness of both Gaussian noise and velvet noise, assigned sample-wise to up to 36 loudspeakers by two algorithms. The first algorithm assigns channels merely by selecting random indices, while the second one constrains the time between two peaks on each channel. The results show that roughness already occurs when few channels are used and that the assignment algorithm influences it. In a second experiment, virtualizations of the test were used to examine the factors contributing to increased roughness. We systematically show the effect of spatial assignment on noise and conclude that besides time-differences, level-differences caused by head-shadowing are the principal cause for the perceived roughness. The results have significance in spatial room impulse response rendering and spatial reverberator design.

Several parametric spatial room impulse response rendering methods use broadband directional estimates, whereby based on sample-by-sample direction-of-arrival estimation, a single channel room impulse response is distributed to multiple loudspeakers. To this end, it has been unclear how such simple parametric processing behaves in the late part of the response. To assess this question, we use simulations and a measurement to show that the commonly applied estimation methods based on the pseudo intensity vector and time difference of arrival estimation do preserve the directional information in the late response. Also, we show that estimated directional differences can be audible under best case conditions. As broadband rendering can sound ‘rough’ or ‘grainy’ for transient input signals due to insufficient pulse density in individual reproduction channels, we use a method to synthesize smooth sounding spatial reverberation. For this, the broadband estimates are used to calculate directional energy envelopes, which are applied to filtered noise sequences. The findings presented here help assessing and improving spatial room impulse response processing methods.

New conference formats are emerging in response to COVID-19 and climate change. Virtual conferences are sustainable and inclusive regardless of participant mobility (financial means, caring commitments, disability), but lack face-to-face contact. Hybrid conferences (physical meetings with additional virtual presentations) tend to discriminate against non-fliers and encourage unsustainable flying. Multi-hub conferences mix real and virtual interactions during talks and social breaks and are distributed across nominally equal hubs. We propose a global multi-hub solution in which all hubs interact daily in real time with all other hubs in parallel sessions by internet videoconferencing. Conference sessions are confined to three equally-spaced 4-h UTC timeslots. Local programs comprise morning and afternoon/evening sessions (recordings from night sessions can be watched later). Three reference hubs are located exactly 8 h apart; additional hubs are within 2 h and their programs are aligned with the closest reference hub. The conference experience at each hub depends on the number of local participants and the time difference to the nearest reference. Participants are motivated to travel to the nearest hub. Mobility-based discrimination is minimized. Lower costs facilitate diversity, equity, and inclusion. Academic quality, creativity, enjoyment, and low-carbon sustainability are simultaneously promoted.

Measured spatial room impulse responses have been used to compare acoustic spaces. One way to analyze and render such responses is to apply parametric methods, yet those methods have been bound to single measurement locations. This paper introduces a method that locates image sources from spatial room impulse responses measured at multiple source and receiver positions. The method aligns the measurements to a common coordinate frame and groups stable direction-of-arrival estimates to find image source positions. The performance of the method is validated with three case studies—one small room and two concert halls. The studies show that the method is able to locate the most prominent image sources even in complex spaces, providing new insights into available Spatial Room Impulse Response (SRIR) data and a starting point for six degrees of freedom (6DoF) acoustic rendering.

The availability of free, user-friendly software tools as well as affordable hardware is boosting interest in higher-order Ambisonics productions not only in research communities, but also in the fields of Pro Audio and Virtual Reality. However, there is no practical solution available for presenting such productions publicly in a web browser. The largest commercial platforms, for example, are limited to first- or second-order binaural playback. We introduce the higher-order Ambisonics streaming platform HOAST, a new 360? video-platform, which allows for up to fourth-order Ambisonics audio material. Apart from implementation details of state-of-the-art binaural decoding and acoustic zoom, this contribution describes the current state of multichannel web audio and related challenges. Non

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This paper proposes a framework for parameterising and rendering spatial room impulse responses, such that monophonic recordings may be reproduced over a loudspeaker array and exhibit the same spatial characteris- tics as the captured space. Due to its general formulation, the rendering framework can either operate directly based on the measured microphone array room impulse responses, or on room impulse responses represented in the spherical harmonic domain. The method employs a sound-eld model comprising a variable number of simultaneous reections, which are combined with an ambient component encapsulating anisotropic diffuse reverberation. The isolated reections are then reproduced over the target loudspeaker array using amplitude- panning, whereas the diffuse reverberation is reproduced over all loudspeakers and subjected to decorrelation operations. The proposed rendering framework has also been made available as an open-source MATLAB toolbox. publishedVersion Non

openaire: EC/HE/812719/EU//VRACE The spatial decomposition method (SDM) is a parametric approach for the processing of spatial room impulse responses. Although extensively used, there are some issues related to used microphone array, reproduction loudspeaker setup, and signal processing that are not widely understood. For example, there have been different observations with regards to its performance with rendering extremely short transient signals, where some authors have described issues such as "roughness" or "graininess". Here, we wish to clarify what the limitations of the spatial decomposition method are and provide practical guidance to ensure the value of SDM as a tool for spatial room impulse response analysis and rendering in various contexts. Specifically, we discuss directional estimation performance, the ability to estimate two reflections at the time, estimation in the late tail of the response, and the roughness and whitening found in the quality of the final rendering. Finally, some post-processing techniques to compensate the possible audible artifacts are reviewed.

In virtual acoustics, it is common to simulate the early part of a Room Impulse Response using approaches from geometrical acous-tics and the late part using Feedback Delay Networks (FDNs). In order to transition from the early to the late part, it is useful to slowly fade-in the FDN response. We propose two methods to con-trol the fade-in, one based on double decays and the other based on modal beating. We use modal analysis to explain the two con-cepts for incorporating this fade-in behaviour entirely within the IIR structure of a multiple input multiple output FDN. We present design equations, which allow for placing the fade-in time at an arbitrary point within its derived limit.

For the evaluation of virtual acoustics for mixed realities, we distinguish between the paradigms "authenticity", "plausibility" and "transfer-plausibility". In the case of authenticity, discrimination tasks between real sound sources and virtual renderings presented over headphones are performed, whereas in case of a plausibility experiment, listeners need to rely only on their expectation of a sound when listening to the rendering, without the presence of an explicit reference. In the case of transfer-plausibility, however, different real sources are active alongside virtual sources, potentially in different spatial locations, leading to a certain degree of comparability. This resembles the case of forthcoming augmented reality systems. Here, we show an experiment, which assesses the transfer-plausibility of rendered speech sources in a variable acoustic environment. We demonstrate the influence of the similarity between real and virtual source material and their spatial location on the transfer-plausibility of measurement-based headphone rendering. Non

We present a study that tests the ability to remember room acoustics – a cognitive skill that is one of the guiding mechanisms behind plausible virtual acoustics for extended realities. Room acoustic memory was tested by assessing a person’s ability to recognise sound samples, convolved with room impulse responses of everyday rooms presented in a preceding training session. To test a common assumption of detection theory, we conducted two listening tests using both a yes/no and a 2AFC paradigm. Results show that subjects can recognise different rooms above chance level, but even with relatively large differences between the rooms, the accuracy is low in general. Furthermore, the relation between the two test paradigms follows the prediction of detection theory when averaging over all participants, but less so for individual participants.