Perceptual Optimization of Room-In-Room Reproduction with Spatially Distributed Loudspeakers

It is often desirable to reproduce a specific room-acoustic scene, e.g. a concert hall in a playback room, in such a way that the listener has a plausible and authentic spatial impression of the original sound source including the room acoustical properties. In this study a perceptually motivated approach for spatial audio reproduction is developed. This approach optimizes the spatial and monaural cues of the direct and reverberant sound separately. More specifically, the (monaural) spectral cues responsible for the timbre and the (binaural) interaural cross correlation (IACC) cues, responsible for the listener envelopment, were optimized in the playback room to restore the auditory impression of the recording room. The direct sound recorded close to the source is processed with an auditory motivated gammatone filterbank such that the spectral cues, ITD’s and ILD’s are comparable to the direct sound in the recording room. Additionally, the reverberant sound, which was recorded at two distant locations from the source, is played back via dipole loudspeakers. Due to the arrangement of the two dipole loudspeakers, only the diffuse sound field in the playback room is excited, therefore the spectral cues and the IACC of the reverberant sound field can be controlled independently to match the cues that were present in the recording room. As indicated by a preliminary listening test the applied optimization is perceptually similar to the reference signal and is generally preferred when compared to a conventional room-in-room reproduction.DFG, FOR 1732, Individualisierte Hörakustik: Modelle, Algorithmen und Systeme für die Sicherstellung der akustischen Wahrnehmung für alle in allen Situatione

Evaluation of Virtual Acoustic Environments with Different Acoustic Level of Detail

Virtual acoustic environments enable the creation and simulation of realistic and ecologically valid daily-life situations with applications in hearing research and audiology. Hereby, reverberant indoor environments play an important role. For real-time applications, simplifications in the room acoustics simulation are required, however, it remains unclear what acoustic level of detail (ALOD) is necessary to capture all perceptually relevant effects. This study investigates the effect of varying ALOD in the simulation of three different real environments, a living room with a coupled kitchen, a pub, and an underground station. ALOD was varied by generating different numbers of image sources for early reflections, or by excluding geometrical room details specific for each environment. The simulations were perceptually evaluated using headphones in comparison to binaural room impulse responses measured with a dummy head in the corresponding real environments. The study assessed the perceived overall difference for a pink pulse, and a speech token. Furthermore, plausibility and externalization were evaluated. The results show that a strong reduction in ALOD is possible while obtaining similar plausibility and externalization as with dummy head recordings. The number and accuracy of early reflections appear less relevant, provided diffuse late reverberation is appropriately accounted for.Comment: This work has been submitted to the I3DA 2023 International Conference on Immersive and 3D Audio for possible publicatio

On the relevance of acoustic measurements for creating realistic virtual acoustic environments

Geometrical approaches for room acoustics simulation have the advantage of requiring limited computational resources while still achieving a high perceptual plausibility. A common approach is using the image source model for direct and early reflections in connection with further simplified models such as a feedback delay network for the diffuse reverberant tail. When recreating real spaces as virtual acoustic environments using room acoustics simulation, the perceptual relevance of individual parameters in the simulation is unclear. Here we investigate the importance of underlying acoustical measurements and technical evaluation methods to obtain high-quality room acoustics simulations in agreement with dummy-head recordings of a real space. We focus on the role of source directivity. The effect of including measured, modelled, and omnidirectional source directivity in room acoustics simulations was assessed in comparison to the measured reference. Technical evaluation strategies to verify and improve the accuracy of various elements in the simulation processing chain from source, the room properties, to the receiver are presented. Perceptual results from an ABX listening experiment with random speech tokens are shown and compared with technical measures for a ranking of simulation approaches.Comment: This work has been submitted to the I3DA 2023 International Conference (IEEE Xplore Digital Library) for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Perceptual and Room Acoustical Evaluation of a Computational Efficient Binaural Room Impulse Response Simulation Method

A fast and perceptively plausible method for synthesizing binaural room impulse responses (BRIR) is presented. The method is principally suited for application in dynamic and interactive evaluation environments (e. g., for hearing aid development), psychophysics with adaptively changing room reverberation, or simulation and computer games. In order to achieve a low computational cost, the proposed method is based on a hybrid approach. Using the image source model (ISM; Allen and Berkley [J.Acoust. Soc. Am. Vol. 66(4), 1979]), early reflections are computed in a geometrically exact way, taking into account source and listener positions as well as wall absorption and room geometry approximated by a “shoebox”. The ISM is restricted to a low order and the reverberant tail is generated by a feedback delay network (FDN; Jot and Chaigne [Proc. 90th AES Conv., 1991]), which offers the advantages of a low computational complexity on the one hand and an explicit control of the frequency dependent decay characteristics on the other hand. The FDN approach was extended, taking spatial room properties into account such as room dimensions and different absorption characteristics of the walls. Moreover, the listener orientation and position in the room is considered to achieve a realistic spatial reverberant field. Technical and subjective evaluations were performed by comparing measured and synthesized BRIRs for various rooms. Mostly, a high accuracy both for some common room acoustical parameters and subjective sound properties was found. In addition, an analysis will be presented of several methods to include room geometry in the FDN.DFG, FOR 1732, Individualisierte Hörakustik: Modelle, Algorithmen und Systeme für die Sicherstellung der akustischen Wahrnehmung für alle in allen SituationenDFG, EXC 1077/1, Hören für alle: Modelle, Technologien und Lösungsansätze für Diagnostik, Wiederherstellung und Unterstützung des Hören

A high resolution head-related transfer function database including different orientations of head above the torso

DFG, 174776315, FOR 1557: Simulation and Evaluation of Acoustical Environments (SEACEN

Computationally-efficient and perceptually-motivated rendering of diffuse reflections in room acoustics simulation

Geometrical acoustics is well suited for simulating room reverberation in interactive real-time applications. While the image source model (ISM) is exceptionally fast, the restriction to specular reflections impacts its perceptual plausibility. To account for diffuse late reverberation, hybrid approaches have been proposed, e.g., using a feedback delay network (FDN) in combination with the ISM. Here, a computationally-efficient, digital-filter approach is suggested to account for effects of non-specular reflections in the ISM and to couple scattered sound into a diffuse reverberation model using a spatially rendered FDN. Depending on the scattering coefficient of a room boundary, energy of each image source is split into a specular and a scattered part which is added to the diffuse sound field. Temporal effects as observed for an infinite ideal diffuse (Lambertian) reflector are simulated using cascaded all-pass filters. Effects of scattering and multiple (inter-) reflections caused by larger geometric disturbances at walls and by objects in the room are accounted for in a highly simplified manner. Using a single parameter to quantify deviations from an empty shoebox room, each reflection is temporally smeared using cascaded all-pass filters. The proposed method was perceptually evaluated against dummy head recordings of real rooms.Comment: This work has been submitted to Forum Acusticum 2023 for publicatio