Journal of the Audio Engineering Society

2020 December - Volume 68 Number 12


Comparison of 3D Audio Reproduction Methods Using Hearing Devices

Authors: Simon, Laurent S. R.; Dillier, Norbert; Wüthrich, Hannes

In order to study 3D auditory perception for hearing aid users, spatial audio reproduction systems have been considered. Numerous solutions were designed in the past, but few studies evaluated the effect of 3D audio reproduction artifacts on hearing devices. This study focuses on loudspeaker-based 3D audio reproduction and compares the effects of distance-based amplitude panning (DBAP), third and fifth order Ambisonics (HOA), multiple-direction amplitude panning (MDAP), and vector-base amplitude panning (VBAP) on the 3D directivity index (DI) of hearing device beamformers, on interaural time differences (ITD), and on interaural level differences (ILD). Measurements were conducted at the sweet spot and for two off-center positions in a non-anechoic room using 32 loudspeakers. Results show that the effect of the reproduction system on the DI at the sweet spot was larger for third order Ambisonics and MDAP and smaller for fifth order Ambisonics. They also show that DBAP cannot reproduce ITDs correctly and that the ILDs obtained with HOA reproduction contain larger errors than with the other reproduction systems. Finally the results show that the DI, ITD, and ILD errors increase with the distance to the sweet spot and that this increase is larger for HOA than for the other reproduction methods.

Psychophysiological Responses of Young People to Soundscapes in Actual Rural and City Environments

Authors: Li, Yanling; Cai, Jun; Dong, Qidi; Wu, Linjia; Chen, Qibing


To investigate the psychophysiological effects of soundscapes in different actual environments, rural and city landscapes were selected as experimental sites, and 30 students were enrolled in this study. The effects of soundscapes were revealed through measured systolic and diastolic blood pressure, heart rate, and electroencephalography of participants before and after introducing soundscape elements to the landscape environment, and the participants rated their preferences. In this study, nature, light music, and symphony soundscape elements decreased systolic and diastolic blood pressure, slowed the heart rate, and increased the ß/a index in the participants, while traffic soundscape elements showed the opposite effects. Furthermore, there were certain differences in the psychophysiological effects of soundscape elements in different landscape scenes, manifested by the result that nature soundscape elements had a greater effect on participants in the rural landscape environment, while light music soundscape elements had a greater effect on participants in the city landscape environment. In addition, men and women presented certain differences in psychophysiological responses to soundscape elements; that is, men preferred symphony soundscape elements in the city landscape environment, and women were more susceptible to the negative effects of traffic soundscape elements in rural or city landscape environments.

The design of a filter inductor for class-D audio amplifiers is investigated, where issues of linearity and bandwidth contribute in addition to losses and size, and inductor modeling is complicated by the combination of high frequency switching and low frequency modulating signals. Two suitable core material types are considered: gapped ferrite and un-gapped powdered metal, illustrating a trade-off between winding and core losses. The potential for improving semiconductor losses by varying inductance value is also demonstrated. Inductor optimization is illustrated in the design and analysis of a 500 WRMS amplifier inductor. It is shown that the powdered core provides the lowest inductor losses, with improvements of up to 60% over a gapped ferrite design. However the potential for significant amplifier improvement is limited by high semiconductor losses

We exploited deep neural networks (DNN) for two-to-five channel surround decoding. Specifically DNNs are used to replace the primary-ambient separation and ambient-signal-rendering modules. For the training, the mean-squared error of the magnitude spectra between the decoded and five-channel target signals and the interchannel level differences between the target signals were used as the loss functions. Through this procedure the DNNs can derive the spectral weights that can be used to produce the decoded signals, similar to that for the target signals. The log spectral distance, signal-to-distortion ratio, and multiple stimuli with hidden reference and anchor tests were used for objective and subjective evaluations. The experimental results show that exploiting the DNNs can generate decoded signals that are more similar to the target signals than those obtained via previous methods.

An Approach for the Optimization of 3D Loudspeaker Horns

Authors: Smolen, Chris; Halley, Jérôme

A method for optimizing three-dimensional loudspeaker horns is described. The acoustical properties of horn geometry parametrized in computer-aided design software are analyzed using finite element analysis and the boundary element method. Through scientific programming, the parametrized horn geometry is manipulated and optimized according to specified objective functions. Experimental measurements of a geometrically nonaxisymmetric horn designed using this method is presented.

Optimizations of the Spatial Decomposition Method for Binaural Reproduction

Authors: Amengual Garí, Sebastià V.; Arend, Johannes M.; Calamia, Paul T.; Robinson, Philip W.


The spatial decomposition method (SDM) can be used to parameterize and reproduce a sound field based on measured multichannel room impulse responses (RIRs). In this paper we propose optimizations of SDM to address the following questions and issues that have recently emerged in the development of the method: (a) accuracy in direction-of-arrival (DOA) estimation with open microphone arrays utilizing time differences of arrival as well as with B-format arrays using pseudo-intensity vectors; (b) optimal array size and temporal processing window size for broadband DOA estimation based on open microphone arrays; (c) spatial and spectral distortion of single events caused by unstable DOA estimation; and (d) spectral whitening of late reverberation as a consequence of rapidly varying DOA estimates. Through simulations we analyze DOA estimation accuracy (a) and explore processing parameters (b) in search of optimal settings. To overcome the unnatural DOA spread (c), we introduce spatial quantization of the DOA as a post-processing step at the expense of spatial distortion for successive reflections. To address the spectral whitening (d), we propose an equalization approach specifically designed for rendering SDM data directly to binaural signals with a spatially dense HRTF dataset. Finally, through perceptual experiments, we evaluate the proposed equalization and investigate the consequences of quantizing the spatial information of SDM auralizations by directly comparing binaural renderings with real loudspeakers. The proposed improvements for binaural rendering are released in an open source repository.

Engineering reports

A Multi-channel Anechoic Orchestra Recording of Beethoven’s Symphony No. 8 op. 93

Authors: Böhm, Christoph; Ackermann, David; Weinzierl, Stefan


For the quality of model-based, virtual acoustic environments, not only the room acoustic simulation but also the quality and suitability of the source material play an important role. An optimal recording of real sound sources is characterized by an anechoic production and a high signal-to-noise ratio and crosstalk attenuation between the different recording channels. Furthermore a recording in the far field of the source is necessary to use correct directivities for room acoustic simulations. From an artistic point of view, the recording situation with its technical boundary conditions must be designed in a way that the musical or vocal rendering of professional performers is impaired as little as possible. To provide a high-quality source signal for acoustic simulations of orchestral content, a professional symphony orchestra was recorded in the anechoic chamber of TU Berlin performing the 8th Symphony of L. v. Beethoven. Through a combination of groupwise and sequential recordings with individual monitor mixes via headphones and video recordings of the conductor and concertmaster, an optimal compromise was sought with regard to artistic and technical aspects. The article presents the recording process and processing chain as well as the results achieved with respect to technical and artistical quality criteria.

Standards and Information Documents

AES Standards Committee News


A workshop presented online during the AES Show Fall 2020 explored how radio broadcasters adapted to the pandemic. Radio operations moved quickly from corporate studios into the home in order to stay on air. A number of the setups and processes adopted during that time are likely to continue even after the pandemic is over. Networking technology makes all this possible.

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