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Journal of the Audio Engineering Society

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2004 November - Volume 52 Number 11

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Papers

Dithered Noise Shapers and Recursive Digital Filters

Authors: Lipshitz, Stanley P.; Wannamaker, Robert A.; Vanderkooy, John

The question of which spectrally shaped dither signals are appropriate for use in quantizing systems, with and without noise shaping error feedback, or in recursive digital filters using dithered quantization at the output, is addressed. It is shown that dithers that are acceptable without feedback present may be unacceptable if feedback is introduced. In each case, certain classes of dither generators are shown to be appropriate for audio applications.

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Motion-Tracked Binaural Sound

Authors: Algazi, V. Ralph; Duda, Richard O.; Thompson, Dennis M.

A new method is presented for capturing, recording, and reproducing spatial sound that provides a vivid sense of realism. The method generalizes binaural recording, preserving the information needed for dynamic head-motion cues. These dynamic cues greatly reduce the need for customization to the listener. During either capture or recording, the sound field in the vicinity of the head is sampled with a microphone array. During reproduction, a head tracker is used to determine the microphones that are closest to the positions of the listener's ears. Interpolation procedures are used to produce the headphone signals. The properties of different methods for interpolating the microphone signals are presented and analyzed.

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Importance and Representation of Phase in the Sinusoidal Model

Authors: Andersen, Tue Haste; Jensen, Kristoffer

Work is presented on the representation and perceptual importance of phase. Based on a standard sinusoidal analysis/synthesis system, the phase alignment of the sound components is analyzed. A novel phase representation, partial-period phase, is introduced, which characterizes phase evolution over time with an almost stationary parameter for many musical sounds. The proposed partial-period phase representation is used to control the phase when synthesizing sounds. Sounds synthesized with varying amounts of phase information are compared in a listening experiment with 11 subjects. It is shown that phase is of great importance to the perception of the sound quality of common harmonic musical sounds, but indications are found that phase is not of importance to the slightly inharmonic piano sounds. In particular, the sound degradation is large for low-pitched sounds, approaching "slightly annoying" when no phase information is used. In addition, a model based on the partialperiod phase representation has a significantly better perceived sound quality than sounds with random phase shifts.

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Direct Approximate Third-Order Response Synthesis of Vented-Box Loudspeaker Systems

Authors: Llamazares, Bernat

A new approach to designing vented-box loudspeaker systems exhibiting approximate third-order responses is presented, and as a result a new family of intermediate alignments is obtained. These alignments are characterized by providing a better transient response at the expense of a less than optimum efficiency in the low-frequency range (provided both fourthand approximate third-order filter functions are adjusted in a similar way). Different cases are illustrated relating to a set of well-known solutions.

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Metadata Revisited: Six New Things to Know About Audio Metadata

Authors: Staff, AES

[feature] Last year we published an article designed to demystify and explain a number of key concepts relating to audio metadata (see JAES July/August 2003). Since that time the field has moved on and the AES 25th International Conference held in London during June 2004 provided an opportunity to find out more about recent developments, as well as topics not covered in the original article. The following is a short summary of some of these, concentrating primarily on audio metadata standards and applications rather than on feature extraction (which was another key concept discussed at the AES 25th Conference).

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Digital Archive Strategies and Solutions for Radio Broadcasting

Authors: Staff, AES

[feature] In this article we review coverage of digital archiving issues for radio broadcasting from the 116th AES Convention, held in May in Berlin, Germany.

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