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Journal of the Audio Engineering Society

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2010 March - Volume 58 Number 3

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Papers

Fast Measurement of Motor Suspension Nonlinearities in Loudspeaker Manufacturing

Authors: Klippel, Wolfgang; Schlechter, Joachim

High-speed measurement of loudspeaker nonlinearity is important to achieving quality testing during manufacturing. Rather than just focusing on a single pass–fail criterion, this study explores how measurements at the loudspeakers terminals can provide diagnostic information about the nonlinearity in the motor and suspension systems. For example, a single valued parameter of voice-coil offset can be derived with signal durations of less than 3 seconds. Using this information as feedback in process control can reduce the rejection rate and increase production yield.

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Spectral and Spatial Parameter Resolution Requirements for Parametric, Filter-Bank-Based HRTF Processing

Authors: Breebaart, Jeroen; Nater, Fabian; Kohlrausch, Armin

In applications such as surround sound reconstruction, the required information in nonindividualized head-related transfer functions (HRTF) can be reduced without producing audible degradation. Estimating the magnitude and interaural phase spectra per critical band is sufficient for transparent parameterization. When reconstructed by interpolation of parameters in the spectral domain, spatial resolution of about 10 degrees proved to be sufficient for high-quality binaural processing. High-frequency phase characteristics proved to be irrelevant, and low-frequency phase can be described only with interaural delay.

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Comparative Study of Design and Implementation Strategies of Automotive Virtual Surround Audio Systems

Authors: Bai, Mingsian R.; Lee, Chih-Chung

Because of their small size, automobiles are a special challenge for implementing a surround sound experience. A comprehensive study explores the tradeoffs of practical implementations. A combination of simulations and experiments showed that inverse filtering is most effective for a single listener, especially in the rear seats. With more than one listener, other approaches are better because the number of inverse filters increases dramatically. The choice of processing depends on the source format: two-channel versus 5.1-channel input.

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Fractional Delay in the Frequency Domain for Beamforming Applications

Authors: Sanchez-Bote, Jose-Luis; Gomez-Alfageme, Juan-Jose

Real-time processing of audio signals in microphone and loudspeaker arrays often requires the implementation of fractional delays. The proposed methods are particularly relevant in applications that use windowing and frequency transforms. The short-time spectrum can be modified to obtain the equivalent delay. Various approaches to the problem are discussed and evaluated in the context of beamforming precision resulting from time-alignment errors.

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Standards and Information Documents

AES Standards Committee News

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Features

Audio in Multimodal Applications

Authors: Rumsey, Francis

[Feature] A papers session held last year at the 127th Convention in New York, “Audio in Multimodal Applications,” highlighted the ways in which audio interacts with other sensory inputs such as visual and tactile ones. Interactive applications for audio within medical environments, games, and installations were discussed, along with novel approaches to spatialization and stereo image correction for displays.

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The 48-Volt Phantom Menace Returns

Authors: Bortoni, Rosalfonso; Kirkwood, Wayne

[Feature] In a paper presented at the 110th AES Convention, Hebert and Thomas described the “phantom menace,” wherein phantom power faults can damage audio input circuitry. Their approach focused on the analysis of a “common-mode fault” occurring at the microphone preamplifier inputs, which was described as a “fault at both inputs, simultaneously.” However, this is not the only fault condition that can occur. New fault mechanisms are considered in this paper, and we show that commonly used protection schemes for popular integrated microphone preamplifiers do not always protect the preamplifiers as expected.

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