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Authors: Yu, Wangyang; Kleijn, W. Bastiaan
Mapping a room impulse response (RIR) to its Ambisonics representation is not always feasible. However, by adding a weak assumption (i.e., the existence of at least two perpendicular walls in the environment), the Ambisonics representation is restricted to be one of a finite set, with known transformations between the set entries. This makes mapping the omnidirectional RIR to the Ambisonics RIR (ARIR) possible. The authors solve the mapping problem with a convolutional neural network and multi-task variational autoencoder. The room is assumed to be rectangular. The proposed method is based on the image source method with frequency independent reflection coefficients exclusively. The authors focus on the early part of RIRs, where the directional information lies. This method requires only a single RIR. Generalizing to the real world, measurements can obviate the need for specialized hardware for Ambisonics measurement. The proposed method can achieve an SNR of 17.62 dB on estimated first-order ARIRs and 16.15 dB on estimated third-order ARIRs.
Authors: Van Ransbeeck, Wannes; De Poortere, Nele; Kok, Marcel; Verhulst, Sarah
Regulations governing sound exposure at amplified-music events aim to safeguard audience’s hearing. However, current sound monitoring practices often rely on a single measurement position that is considered representative of individual exposure. Because this standard practice overlooks crucial inter-subject variation in sound exposure, this study analyzes individual dosimeter sound level exposure at large-scale music events to gain insight into this matter while comparing findings to local and global guidelines. Dosimeters were worn by 42 participants (19 female and 23 male, aged 18–25) and recorded octave bands and A/C-weighted sound levels at six large-scale music events (+4.000 visitors). Individual single-day exposure duration varied between 4.4 and 11.8 h. At four out of the six events, individual doses surpassed the WHO 100 dBA LAeq,15min recommendation, with most subjects also exceeding the ISO Standard 1999:2003 occupational limit and the WHO’s 100-dBA-for-4-h threshold (16 Pa2h). Equivalent exposures spanned 85.2–104.5 dBA (LAeq) and 97.1–119.6 dBC (LCeq) among participants. Additionally, LCpeak values fluctuated between 133.6 and 143.5 dBC. These findings highlight a discrepancy between the fixed-location exposure monitoring, as per country-specific legislation, and the actual potentially harmful exposure experienced by event attendees. These results can inspire safe-listening guidelines for such music events and offer insight into the representative degree of a single-position measure.
Authors: Riionheimo, Janne; Lokki, Tapio
Room acoustics and sound reproduction systems shape the spatial sound character in a listening room, influencing sound quality. This study introduces a novel technique to assess the spatial character of room acoustics and sound reproduction systems, addressing a research gap in understanding spatial differences between listening environments. The technique was employed in a listening test where 15 assessors evaluated the impact of three listening rooms on perceptual immersion for music in 2.0 and 7.1 configurations using loudspeakers and binaural audio for headphones. The results indicate room reverberation enhances perceptual immersion, particularly with two-channel stereophonic setups. Surround speakers reduce room-induced effects when the music is mixed sufficiently enveloping, especially with distinct, nonreverberant surround elements. The results with headphones were similar but less pronounced. Assessors found the normal stereo tonally preferable to binaural conditions, but perceptions of immersiveness varied. Some described it as highly immersive, whereas others reported a lack of spatial depth, although it was perceived as supernaturally wide and effective compared with binaural sound. This highlights the challenge of transitioning from normal stereo to a spatialized mix in streaming services. Overall, the findings can enhance the immersive experience and even out perceptual differences between listening environments, including loudspeakers and headphones.
Authors: Riionheimo, Janne; Lokki, Tapio
The spatial sound character in a listening room is influenced by both the room acoustics and the sound reproduction system. These elements, either individually or in combination, can improve or reduce the sound quality. This study investigates the impact of room acoustics and electroacoustics on the sound character of popular mainstream music mixed in 7.1 and 7.1.4 formats. Fourteen skilled assessors evaluated the impact on envelopment, clarity, proximity, and preference. As one might expect, the results suggest that room reverberation improves envelopment and preference. Surprisingly, most assessors found that reverberation also brings clarity to the music. Conversely, dry acoustics were not considered preferable, nor did they improve the proximity for the majority of assessors. Adding overhead channels made punk and rock songs more enveloping but improved the preference only with the simple sound field of a ballad. Overall, the results can help improve spatial sound quality and make it easier for sound mixers to deliver consistent immersive sound experiences to listeners.
Authors: Lübeck, Tim; Weber, Tobias; Pörschmann, Christoph
Plausibility has become a widely used paradigm for evaluating binaural audio for augmented reality. Although several studies have evaluated the plausibility of different binaural rendering techniques, it is not clear which parameters contribute to plausibility and to what extent. The present study attempts to fill this gap and presents the results of five listening experiments systematically investigating the impact of different parameters. A first plausibility test performed in anechoic conditions assessed the plausibility of nonindividual head-related transfer-function rendering. In four subsequent experiments, the influence of spherical harmonics truncation order, visual cues, small translational head movements, and different head-related transfer-function sets is assessed. Overall, the results indicate that even large manipulations of the rendering system have surprisingly little impact on the estimated d’.
Authors: Bakardjiev, Petko; Marschner, Uwe; Richter, Andreas; Altinsoy, Ercan
A novel loudspeaker design integrating lightweight and efficient acoustic transducers derived from dielectric elastomer films is presented. This innovation centers on core-free dielectric elastomer roll actuators, functioning akin to artificial muscles, altering shape upon the application of an electric field. The actuators serve two roles: propelling acoustically radiating surfaces and emitting sound themselves. The paper provides a model that describes the axial vibration behavior via electromechanical and acoustic networks, facilitating understanding and comparability with electrodynamic loudspeaker systems without the need for extensive background knowledge of dielectric elastomer technology. Based on established methodologies, the design process and adaptability to diverse applications is evident. A demonstrator developed as a proof of concept with the aim of creating a broadband speaker for speech reproduction was designed, constructed, and examined utilizing the established methodology. It shows promising practicality and, in certain aspects, technological superiority over electrodynamic counterparts. Notable features, such as increased efficiency, significant weight reduction, and wide radiation pattern make this speaker viable and particularly attractive for mobile PA applications such as those found in trains and aircraft. Furthermore, the underlying principle and modeling framework allow the future creation and adaptation to a broad spectrum of applications, promising further innovation in the field.
Authors: Hilgemann, Florian; Chatzimoustafa, Egke; Jax, Peter
Active noise control (ANC) has become popular for reducing noise and thus enhancing user comfort in headphones. Although feedback control offers an effective way to implement ANC, it is restricted by uncertainty of the controlled system (e.g., that arises from differing wearing situations). Widely used unstructured models that capture these variations tend to overestimate the uncertainty and thus restrict ANC performance. As a remedy, this work explores uncertainty models whose shapes are derived from experimentally determined measurement data to improve ANC performance for over-ear and in-ear headphones. The controller optimization based on these models is described, and an ANC prototype is implemented to compare the performances associated with conventional and proposed modeling approaches. Extensive measurements with human wearers confirm the robustness and indicate a performance improvement over conventional methods. The results allow to increase the active attenuation of ANC headphones by several decibels at no loss of stability.
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