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Journal of the Audio Engineering Society

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2009 October - Volume 57 Number 10

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Papers

New Methodology for the Acoustic Design of Compression Driver Phase Plugs with Concentric Annular Channels

Authors: Dodd, Mark; Oclee-Brown, Jack

Compression drivers couple a radiating diaphragm to a horn throat of smaller area, resulting in high efficiency. Commonly a phase plug is used to control the transition from diaphragm to horn in order to improve the high-frequency performance. In this paper a new design method for the positioning of annular phase plug channels is presented in order to improve the driver response.

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Automatic Language Recognition on Spontaneous Speech: The ATVS-UAM System

Authors: Toledano, Doroteo T.; Lopez-Moreno, Ignacio; Mateos, Ismael; Abejon, Alejandro; Ramos, Daniel; Gonzalez-Rodriguez, Joaquin

Automatic recognition of the language of spontaneous speech is a difficult problem that has been studied for years. This article provides a brief introduction to the general topic and an examination of a specific implementation that has already achieved a level of performance adequate for real applications. A detailed performance analysis provides a comparison of various techniques in terms of recognition accuracy and computational costs. Error rates of 5% and systems running eight-times real time have already been achieved. Issues of training on learning data and evaluation databases are addressed.

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High-Definition Audio Spectrum Separation via Frequency Response Masking Filter Banks

Authors: Lin, Ching-Shun; Kyriakakis, Chris

In this paper a general structure for two-band filter banks with rational sampling factors is proposed to arbitrarily separate the audio spectrum. The authors extended a quadrature mirror filter (QMF) bank to unevenly decompose spectra into a specific ratio and then reconstructed them with negligible distortion. To achieve high-precision filter banks and reduce the implementation cost, the authors also integrated the rational filter banks with the frequency response masking (FRM) approach for the digital filter bank design. This procedure can be applied to filter banks with both integer and rational decimation factors.

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Engineering reports

Wide-Range Electrostatic Loudspeaker with a Zero-Free Polar Response

Authors: White, D. R.

A floor-to-ceiling electrostatic doublet loudspeaker uses a symmetric RC transmission line to equalize the frequency response and to give a zero-free polar pattern. Such equalization ensures that the entire electrostatic loudspeaker (ESL) panel contributes acoustic energy at low frequencies. The critical design parameters are the total capacitance of the panel and the intersegment coupling resistance of the transmission line. These parameters provide a tradeoff among midband sensitivity, high-frequency polar response, and low-frequency cutoff. Computer models were used to evaluate the performance of the proposed design.

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Standards and Information Documents

AES Standards Committee News

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Features

On the Move with Multichannel

Authors: Rumsey, Francis

[Feature] When users need to be able to move around in spatial soundfields, multichannel systems are needed that can cover a wide listening area. Zoned reproduction, on the other hand, enables listeners in different parts of the soundfield to hear different things with minimal interference between zones. If a listener wants multichannel sound to move with him when out and about, then some form of headphone rendering is desirable. Multichannel systems such as wavefield synthesis and Ambisonics have the potential to create realistic soundfields over wide listening areas, but they have specific limitations and are not capable of identical performance.

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High Definition Television: An Update for Audio Engineers

Authors: Rumsey, Francis

[Feature] Audio engineers need to be aware of developments in their sister domain of the television industry. The topic driving television forward at the moment is high definition (HD), and the latest developments in this field were aired to a large audience at the HD Masters conference chaired by John Ive and held in London in June 2009. The conference was a joint venture between TVB Europe, BKSTS, and SMPTE. In this short article we provide a summary of some of the trends evident in HD television, as well as related audio issues.

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