This article details and evaluates three alternative approaches to sound-field visualization, which all employ the use of spatially-localized active-intensity (SLAI) vectors. SLAI vectors are particularly interesting as they allow direction-of-arrival (DoA) estimates to be extracted in multiple spatially-localized sectors, such that sound sources and/or noise present in one sector has reduced influence on the DoA estimate made in the other sectors. These DoA estimates may then be used to...

Advanced automotive applications like Active Noise Cancellation (ANC) and Individual Listening Zones (ILZ) require a high number of transducers (i.e., microphones, accelerometers, and loudspeakers) usually arranged as arrays. Transducer arrays are widely employed in several applications besides automotive field, such as teleconferencing systems, industrial and civil monitoring of noise and vibrations. Automotive Audio Bus ( $\text{A}^{2}\text{B}$ ) is an audio transport protocol that solves the latest requirements of automotive and industrial fields. $\text{A}^{2}\text{B}$ allows transporting up to 32 channels in a multi-node daisy chain network and guarantees synchronization and low deterministic latency. This paper aims to develop a clock propagation model of an $\text{A}^{2}\text{B}$ network composed by transducer arrays. This model will be useful to evaluate the impact of the bus on the array performance. Firstly, a theoretical description of the $\text{A}^{2}\text{B}$ protocol and jitter analysis is provided. It follows a description of the jitter measures carried out on the clocks distributed along the $\text{A}^{2}\text{B}$ network. Lastly, latency introduced by nodes of the network is investigated.

Microphone arrays of various sizes and shapes are currently employed in consumer electronics devices such as speakerphones, smart TVs, smartphones, and headphones. In this paper, a full-digital, planar microphone array is presented. It makes use of digital Micro Electro-Mechanical Systems (MEMS) microphones, connected through the Automotive Audio Bus (A2B). A clock propagation model for A2B networks, developed in a previous work, was employed to estimate the effects of jitter and delay on microphone arrays. It will be shown that A2B allows for a robust data transmission, while ensuring deterministic latency and channels synchronization, thus overcoming the signal integrity issues which usually affect MEMS capsules. The microphone positioning is also discussed since it greatly affects the spatial accuracy of beamforming. Numerical simulations were performed on four regular geometries to identify the optimal layout in terms of number of capsules and beamforming directivity. An A2B planar array with equilateral triangle geometry and four microphones, three in the vertices and one in the center, was built. Experimental measurements were performed, obtaining an excellent matching with numerical simulations. Finally, the concept of an array of arrays (meta-array) is presented, designed by combining several triangular units and analyzed through numerical simulations.

Microphone arrays of various sizes and shapes are widely employed in consumer electronics devices such as smart speakers, speakerphones, smart TVs, smartphones, PCs, and headphones. Therefore, the possibility of creating arrays of arrays (i.e., meta-arrays), by easily connecting several smaller units, is particularly interesting: it allows for different shapes, with an increased number of microphones and improved performance, while keeping costs low. In this paper, full-digital microphone meta-arrays are presented: they are constituted by an arrangement of several triangular units, each featuring four digital Micro Electro-Mechanical Systems (MEMS) capsules connected in daisy-chain through the Automotive Audio Bus (A2B). Two prototypes have been built: a planar meta-array made of seven triangles (28 capsules) and a 3-dimensional meta-array with 14 triangles (56 capsules). Numerical simulations were carried out and compared against experimental measurements performed on the prototypes, showing an excellent matching. Finally, the 3-dimensional meta-array was compared with a spherical microphone array widely considered the state-of-the-art equipment in the last decade, demonstrating its potential in telecommunication applications.

In this paper, a technique is described for obtaining the High Order Ambisonics (HOA) Impulse Responses (IRs) of an automotive infotainment system, relying on Finite Elements Method (FEM) simulations performed in COMSOL Multiphysics. The resulting HOA IRs are employed for auralizing the car sound system, either inside an Ambisonics listening room with a loudspeaker rig or with binaural rendering on a Head Mounted Display (HMD), benefiting from head-tracking and personalized Head Related Transfer Functions (HRTFs). This allows performing subjective tests before the prototype is built and preserving the auditory experience with a degree of realism unattainable with the static binaural approach. Measurements performed in a prototype vehicle with a spherical microphone array are compared to FEM simulations. A good agreement between numerical and experimental methods have been demonstrated.

The interest in 3D audio is constantly growing, thus leading to the appearance on the market of many microphone arrays for recording spatial audio, having a variety of sizes, number of channels and shapes, mostly spherical. Among the various characteristics that may have an influence on the quality of these systems, the presented work will deal with the spatial accuracy. The availability of robust methods for evaluating the spatial performance of the microphone arrays allows to compare the systems and to study the effect of different geometries, or beamforming algorithms. On one side, the design of new solutions can be optimized, on the other side a user can identify an optimal system depending on his needs. In this paper, two metrics for evaluating the spatial performance of microphone arrays are described, and two common formats for spatial audio are employed, Ambisonics and Spatial PCM Sampling (SPS). In the first part, the parameters Spatial Correlation and Level Difference are used for assessing the accuracy of the Ambisonics format, which is based on Spherical Harmonics functions. In the second part two classic metrics for loudspeakers, i.e., directivity factor and half power beam width, are employed for evaluating the accuracy of unidirectional virtual microphones, which constitute the base of the SPS format. In the last section, four well-known spherical microphone arrays are analyzed and compared through the described metrics and spatial audio formats.