A particle velocity sensor to measure the sound from a structure in the presence of background noise

The performance (or quality) of a product is often checked by measuring the radiated sound (noise) from the vibrating structure. Often this test has to be done in an environment with background noise, which makes the measurement difficult. When using a (pressure) microphone the background noise can be such that it dominates the radiated sound from the vibrating structure. However, when using a particle velocity sensor, the Microflown [1,2], near the vibrating structure, the background noise has almost no influence (it is almost cancelled) and the sound from the structure is measured with a good S/N ratio. The experimental results are explained in terms of the different boundary conditions at the surface of the vibrating structure for the pressure and the particle velocity

Three-dimensional sound intensity measurements using microflown particle velocity sensors

This paper reports on a novel method to measure three-dimensional sound intensity and the fabrication of a miniature three-dimensional sound intensity probe. Verifying measurements where performed with three separate micromachined particle velocity probes and one pressure microphone. A three-dimensional sound intensity probe has been realised based on a three-dimensional micromachined particle velocity microphone, a 3D Microflown, and a miniature pressure microphon

Magnetic behaviour of narrow track thin-film heads

The influence of the trackwidth on the performance of thin film heads has been tested. Results of experiments on the wafer have indicated an increase in the head efficiency with decreasing trackwidth. This was underlined by measurements of the head fringe field and tape recording experiments. A model which takes the domain structure into account has been developed to interpret this behaviour

Providing Spatial Control in Personal Sound Zones Using Graph Signal Processing

[EN] Personal audio systems aim to create listening (or bright) and quiet (or dark) zones in a room using an array of loudspeakers. For this purpose, many algorithms have been presented in the literature, being Weighted Pressure Matching (wPM) one of the most versatile. The main strength of wPM is that it can render a target soundfield in the listening zone while having control over the mean acoustic potential energy in the quiet zone. In this paper, we propose a variation of wPM such that it can provide control not only over the mean energy, but also over the spatial energy differences, obtaining a more uniform soundfield in the dark zone. The new algorithm is called wPM with Total Variation (wPM-TV), where TV is a tool used in the field of Graph Signal Processing (GSP). Firstly, we propose a graph representation of the control microphones of the dark zone and secondly, we use the wPM-TV algorithm to provide spatial control over that zone. Simulations show the good performance of the proposed algorithm and its versatility to obtain a more uniform distribution of the acoustic potential energy in the dark zone at the cost of slightly increasing the mean square reproduction error in the bright zone.This work has been partially supported by Spanish Ministry of Science, Innovation and Universities through grant FPU17/01288 and by European Union together with Spanish Government through grant RTI2018-098085-BC41 (MCIU/AEI/FEDER)Molés-Cases, V.; Piñero, G.; Gonzalez, A.; Diego Antón, MD. (2019). Providing Spatial Control in Personal Sound Zones Using Graph Signal Processing. IEEE. 1-7. https://doi.org/10.23919/EUSIPCO.2019.8903068S1

Conformal lattice of magnetic bubble domains in garnet film

We report experimental observations of magnetic bubble domain arrays with no apparent translational symmetry. Additionally the results of comparative numerical studies are discussed. Our goal is to present experimental evidence for natural occurence of conformal structures.Comment: 7 pages, 2 figures, LaTeX2e, accepted as paper E090 at JEMS'01 (Joint European Magnetic Symposia, formerly EMMA + MRM), August 28th to September 1st, 2001, Grenoble, Franc

Transition from Townsend to glow discharge: subcritical, mixed or supercritical

The full parameter space of the transition from Townsend to glow discharge is investigated numerically in one space dimension in the classical model: with electrons and positive ions drifting in the local electric field, impact ionization by electrons ($\alpha$ process), secondary electron emission from the cathode ($\gamma$ process) and space charge effects. We also perform a systematic analytical small current expansion about the Townsend limit up to third order in the total current that fits our numerical data very well. Depending on $\gamma$ and system size pd, the transition from Townsend to glow discharge can show the textbook subcritical behavior, but for smaller values of pd, we also find supercritical or some intermediate ``mixed'' behavior. The analysis in particular lays the basis for understanding the complex spatio-temporal patterns in planar barrier discharge systems.Comment: 12 pages, 10 figures, submitted to Phys. Rev.

An approach to generating two zones of silence with application to personal sound systems

An application of current interest in sound reproduction systems is the creation of multizone sound fields which produce multiple independent sound fields for multiple listeners. The challenge in producing such sound fields is the avoidance of interference between sound zones, which is dependent on the geometry of the zone and the direction of arrival of the desired sound fields. This paper provides a theoretical basis for the generation of two zones based on the creation of sound fields with nulls and the positioning of those nulls at arbitrary positions. The nulls are created by suppressing low-order mode terms in the sound field expansion. Simulations are presented for the two-dimensional case which shows that suppression of interference is possible across a broad frequency audio range