Transducer Arrays Over A²B Networks in Industrial and Automotive Applications: Clock Propagation Measurements (original) (raw)
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IEEE Transactions on Consumer Electronics
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 (A 2 B). A clock propagation model for A 2 B networks, developed in a previous work, was employed to estimate the effects of jitter and delay on microphone arrays. It will be shown that A 2 B 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 A 2 B 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. Index Terms-Automotive Audio Bus (A 2 B), automotive applications, beamforming, consumer products, digital MEMS microphones, meta-arrays, microphone arrays, planar arrays, spatial audio, triangular arrays. I. INTRODUCTION M ICROPHONE arrays are employed in consumer electronic devices for several applications, such as teleconferencing, speakerphone units, smartphones, and smart TVs. They are mainly used for dereverberation or echo reduction [1]-[4] and speech recognition [5]. Other consumer electronics applications may include Active Noise Control (ANC) [6], [7], multi-channel audio recording [8] and beamforming [9]. When designing such multichannel systems, the type of capsules and data
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Best Practices in Network Audio - AES WHITE PAPER
J. Audio Eng. Soc, 2009
Analog audio needs a separate physical circuit for each channel. Each microphone in a studio or on a stage, for example, must have its own circuit back to the mixer. Routing of the signals is inflexible. Digital audio is frequently wired in a similar way to analog. Although several channels can share a single physical circuit (e.g., up to 64 with AES10), thus reducing the number of cores needed in a cable. Routing of signals is still inflexible and any change to the equipment in a location is liable to require new cabling. Networks allow much more flexibility. Any piece of equipment plugged into the network is able to communicate with any other. However, installers of audio networks need to be aware of a number of issues that affect audio signals but are not important for data networks and are not addressed by current IT networking technologies such as IP. This white paper examines these issues and provides guidance to installers and users that can help them build successful networked systems.
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Audio communication on the public Internet suffers from not synchronized word clocks of the involved audio devices. The resulting clock drift leads to audio dropouts, which is typically compensated by a sample rate conversion (SRC) in standard telecommunication systems. This, however, does not fulfill the requirements of a high-quality audio system, in which all devices share one and the same word clock. Professional IP based network audio systems such as DANTE or AVB with their respective clock synchronization techniques have so been limited to LAN usage, where network jitter and loss have negligible importance regarding the required accuracy in the dimension of several nanoseconds. In a WAN, however, jitter in the millisecond dimension would lead to unacceptable measurement errors for the intended clock synchronization. As a consequence, we decided to investigate alternative clock synchronization techniques for WAN-distributed devices and developed a GNSS-based approach, which lea...
AES White Paper: Best Practices in Network Audio
Analog audio needs a separate physical circuit for each channel. Each microphone in a studio or on a stage, for example, must have its own circuit back to the mixer. Routing of the signals is inflexible. Digital audio is frequently wired in a similar way to analog. Although several channels can share a single physical circuit (e.g., up to 64 with AES10), thus reducing the number of cores needed in a cable. Routing of signals is still inflexible and any change to the equipment in a location is liable to require new cabling. Networks allow much more flexibility. Any piece of equipment plugged into the network is able to communicate with any other. However, installers of audio networks need to be aware of a number of issues that affect audio signals but are not important for data networks and are not addressed by current IT networking technologies such as IP. This white paper examines these issues and provides guidance to installers and users that can help them build successful networked systems.