Parametric Array Loudspeakers and Applications in Active Noise Control

University of Technology Sydney. Faculty of Engineering and Information Technology.Parametric array loudspeakers (PALs) are known for their capability of generating highly directional audio sound waves. Owing to this feature, they are used as secondary sources in active noise control (ANC) systems to mitigate the unwanted noise in the target regions whilst at the same time minimizing spillover effects on other areas. The primary aim of this thesis is to investigate the feasibility of using multiple PALs in an ANC system to create a large quiet zone. To achieve this, a partial wave expansion model is proposed first based on the quasilinear solution of both Westervelt and Kuznetsov equations to predict the audio sound generated by a PAL in a free field. The model is then extended to accommodate reflection, transmission, and scattering phenomena, which are common in real applications and can have significant effects on the noise reduction performance of ANC systems. The proposed model is validated by experiments conducted in anechoic rooms, and the validated model incorporated with the multi-channel ANC theory is then used to investigate the quiet zone size controlled by multiple PALs. It is found the existing prediction models for PALs are either inaccurate or time-consuming, while the proposed model is more than 100 times faster in both near and far fields without any loss of accuracy. It therefore enables reliable and fast simulations for multi-channel ANC systems, which require heavy computations due to large numbers of PALs. A key finding is that the directivity of the audio sound generated by a PAL is severely deteriorated if sound waves are reflected from a non-rigid surface, truncated by a thin partition, or scattered by a sphere (simulating a human head). This implies the sharp directivity for PALs is not guaranteed as expected when they are used in complex acoustic environments. Finally, both simulations and experiments showed that multiple PALs can create a large quiet zone of comparable size when compared to traditional omnidirectional loudspeakers. However, the spillover effects of using PALs on the sound field outside the quiet zone are much smaller, which demonstrates PALs provide a promising alternative as secondary sources in multi-channel ANC systems

Short overview of parametric loudspeakers array technology and its implications in spatialization in electronic music

UID/EAT/00472/2013In late December of 1962, a Physics Professor\from Brown University, Peter J. Westervelt,\submitted a paper called Parametric Acoustic Array considered primary waves interacting within a given volume and calculated the scattered pressure field due to the non-linearities within a small portion of this common volume in the medium. Since then, many outputs of this technology were developed and applied in contexts such as military, tomography, sonar technology, artistic installations and others. Such technology allows perfect sound directionally and therefore peculiar expressive techniques in electroacoustic music, allowing a very particular music dimension of space. For such reason, it’s here treated as a idiosyncrasy worth to discuss on its on terms. In 2010-2011 I composed the piece "A Anamnese das Constantes Ocultas", commissioned by Grupo de Música Contemporânea de Lisboa, that used a parametric loudspeakers array developed by engineer Joel Paulo. The same technology was used in the 2015 acousmatic piece “Jeux de l'Espace ” for eight loudspeakers and one parametric loudspeaker array. This paper is organized as follows. A theoretical framework of the parametric loudspeaker array is first introduced, followed by a brief description of the main theoretical aspects of such loudspeakers. Secondly, there is a description of practices that use such technology and their applications. The final section describes how I have used it in my music compositions.publishersversionpublishe

High-efficiency collimation of airborne sound through a single deep-subwavelength aperture in an ultra-thin planar plate

© 2019 The Japan Society of Applied Physics. We propose a mechanism for high-efficiency collimation of airborne sound through an ultra-thin planar structure perforated with a single deep-subwavelength aperture by combining a zigzag-shaped structure with arrays of subwavelength resonators to increase the equivalent refractive index and eliminate high-order diffractive waves simultaneously. Numerical simulations demonstrate that the proposed mechanism enables remarkably enhanced transmission and strong collimation of the transmitted wave, which propagates for a strikingly long distance exceeding 125 wavelengths. Due to its capabilities and flexibility, the proposed design opens up possibilities for novel compact acoustic-steering devices and may have far-reaching impacts in diverse applications such as acoustic communications and loudspeaker design

On the design of a (H)EV steerable warning device using acoustic beam forming and advanced numerical acoustic simulation

This paper describes the simulation-based design methodology used in the eVADER project for the development of targeted acoustic warning devices for increased detectability of Hybrid and Electric Vehicles (HEVs) while, at the same time, reducing urban noise pollution. A key component of this system is an external warning signal generator capable of projecting the warning signals to a contained area in front of the vehicle where potential at-risk situations are detected. Using acoustic beam forming principles a suitable warning strategy and an initial layout for realizing such a system is defined. Starting from this information, acoustic Finite and Boundary Element models of the transducer array allow assessing more realistically the performance impact of the system integration and of the most critical changes in the acoustic environment in which the signal generator needs to operate

Beam-steerng digital num array paramétrico

Mestrado em Engenharia Electrónica e TelecomunicaçõesActualmente existem diversos m etodos que permitem a realiza c~ao de beamsteering num altifalante param etrico. No entanto, a maioria dos m etodos e incapaz de proporcionar uma elevada resolu c~ao angular usando um projecto de hardware e ciente. Mais ainda, poucos s~ao os sistemas que proporcionam um controlo do beam de pot^encia em tempo real. Neste documento, e proposta uma nova abordagem para colmatar estes problemas tirando partido da alta frequ^encia inerente a modula c~ao sigmadelta. Esta implementa c~ao leva a um projecto compacto que proporciona uma elevada resolu cao angular associada a uma solu c~ao de baixo custo e com baixo consumo de pot^encia devido ao uso de apenas uma DAC sigmadelta. O sistema implementado sobre FPGA alia a natural alta frequ^encia dum modulador sigma-delta ao uso dum unico shift-register para introduzir os atrasos necess arios a realiza c~ao de beam-steering. A escolha do atraso adequado e feita com o uso de multiplexers que encaminham os diversos sinais sigma-delta para as sa das do sistema desejadas.Several methods enable a steerable beam using an parametric loudspeaker. However, many of them are not able to use a high angular resolution with an e cient design. More, even the ability to change the beam steering in real time is neglected by several methods. In this document, we propose a new approach to the beam-steering problem using the intrinsic high frequency of a sigma-delta digital to analog converter conjugated with online con gurable digital delays obtained only through a programmable wide shift-register. This implementation leads to a real time beam-steering with a simple digital processing block that enables a high resolution angle. Additionally the use of a sigma-delta DAC provides a low-cost, highly integrated and energy e cient system using only a DAC. The implemented system takes advantage of the high frequency of the digital signal from the sigma-delta modulator allied with the use of a shiftregister to obtain the ne time delays necessary to do the beam-steering. The several outputs delays are chosen between the sigma-delta signals in the shift-register using a group of multiplexers

Beam-steering digital num array paramétrico

Engenharia Electrónica e TelecomunicaçõesActualmente existem diversos m etodos que permitem a realiza c~ao de beamsteering num altifalante param etrico. No entanto, a maioria dos m etodos e incapaz de proporcionar uma elevada resolu c~ao angular usando um projecto de hardware e ciente. Mais ainda, poucos s~ao os sistemas que proporcionam um controlo do beam de pot^encia em tempo real. Neste documento, e proposta uma nova abordagem para colmatar estes problemas tirando partido da alta frequ^encia inerente a modula c~ao sigmadelta. Esta implementa c~ao leva a um projecto compacto que proporciona uma elevada resolu cao angular associada a uma solu c~ao de baixo custo e com baixo consumo de pot^encia devido ao uso de apenas uma DAC sigmadelta. O sistema implementado sobre FPGA alia a natural alta frequ^encia dum modulador sigma-delta ao uso dum unico shift-register para introduzir os atrasos necess arios a realiza c~ao de beam-steering. A escolha do atraso adequado e feita com o uso de multiplexers que encaminham os diversos sinais sigma-delta para as sa das do sistema desejadas.Several methods enable a steerable beam using an parametric loudspeaker. However, many of them are not able to use a high angular resolution with an e cient design. More, even the ability to change the beam steering in real time is neglected by several methods. In this document, we propose a new approach to the beam-steering problem using the intrinsic high frequency of a sigma-delta digital to analog converter conjugated with online con gurable digital delays obtained only through a programmable wide shift-register. This implementation leads to a real time beam-steering with a simple digital processing block that enables a high resolution angle. Additionally the use of a sigma-delta DAC provides a low-cost, highly integrated and energy e cient system using only a DAC. The implemented system takes advantage of the high frequency of the digital signal from the sigma-delta modulator allied with the use of a shiftregister to obtain the ne time delays necessary to do the beam-steering. The several outputs delays are chosen between the sigma-delta signals in the shift-register using a group of multiplexers

Simulation-based design of a steerable acoustic warning device to increase (H)EV detectability while reducing urban noise pollution

This paper describes the simulation-based design methodology used in the eVADER project for the development of targeted acoustic warning devices for increased detectability of Hybrid and Electric Vehicles (HEVs) while, at the same time, reducing urban noise pollution compared to conventional acoustic pedestrian warning systems. A key component of this system is an external warning signal generator capable of projecting the warning signals to a contained area in front of the vehicle where potential at-risk situations are detected. Using acoustic beam forming principles a suitable warning strategy and an initial layout for realizing such a system is defined. Starting from this information, acoustic Finite and Boundary Element models of the transducer array allow assessing more realistically the performance impact of the system integration and of the most critical changes in the acoustic environment in which the signal generator needs to operate