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

Design and Implementation of Sound Projector Using a 30-Element Loudspeaker

Projecte final de carrera fet en col.laboració amb School of Electrical Engineering (KTH)For many years, the surround sound effect could only be fully experienced by setting up several speakers, which required considerable wiring for installation in a typical room. Digital sound projectors, one of the most sought-after state-of-the-art solutions, use an array of small speakers enclosed in a box to provide surround by creating virtual sound sources around the listener. This thesis presents a DSP implementation of a simple digital sound projector based on a uniform linear array of thirty loudspeakers. Surround is produced by controlling separate beams of sound. These are reflected off the walls and arrive at the listener’s position from the desired directions. Due to hardware constrains, the bandwidth of the sound is limited. In order to estimate the direction of the sound at the listener, two techniques based on estimating the time difference of arrival (TDOA), Classical Cross-Correlation (CC) and Cross-Correlation with the Source Signal (CSS), are compared. Objective test results show that the CSS technique is more robust than CC under noisy environments, while both techniques behave similarly in quiet conditions. Subjective and objective results show that this implementation of a sound projector is successful, even if front virtual channels are better perceived by the listener than the rear channels