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Journal of the Audio Engineering Society

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2008 July/August - Volume 56 Number 7/8

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Papers

Concert Hall Acoustics—2008

Authors: Beranek, Leo L.

A comprehensive review of concert hall acoustics shows a clear relationship between measurements and perceived quality among listeners, conductors, and musicians. While the basic Sabine and Eyring equations are still important for determining reverberation times, there are other measures that are also important. These include rise and decay of sound energy, early decay at mid-frequencies, lateral fraction, binaural quality index, perceived loudness, listener envelopment, and others. These measures must be connected to the subjective ratings of concert halls that have been accumulated over the years. The principles are illustrated with case studies that compare the shoebox shape to the surround design.

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Noncontact Surface Metrology for Preservation and Sound Recovery from Mechanical Sound Recordings

Authors: Boltryk, P. J.; McBride, J. W.; Hill, M.; Nascè, A. J.; Zhao, Z.; Maul, Christian

Decoding historic mechanical recordings using noncontact optical methods avoids further degradation that would be created with a stylus. Moreover, for recordings that have been damaged, contact methods do not work. The proposed method, which is based on surface metrology of engineering surfaces, measures the surface optically, while offline signal processing then recovers the audio information. The surface record, preserved as a high-resolution matrix grid, is retained indefinitely. Preliminary results indicate better noise and distortion performance compared to mechanical playback.

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Automatic Musical Genre Classification Using a Flexible Approach

Authors: Barbedo, Jayme Garcia Arnal; Lopes, Amauri

An automated method for classifying music signals into genres is proposed. Up to three genres are assigned to each example along with a measure of the degree of influence. The method is based on a structure formed by taxonomy of four hierarchical layers, with 29 genres in the lowest layer and 10 target genres in the higher layers. In more than 77% of the cases there was successful classification. The computational effort is sufficiently low that this method could be used in real time.

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Modeling Frequency-Dependent Boundaries as Digital Impedance Filters in FDTD and K-DWM Room Acoustics Simulations

Authors: Kowalczyk, Konrad; Walstijn, Maarten van

A novel method for modeling frequency-dependent boundaries in finite-difference time-domain (FDTD) room acoustic simulations offers a significant improvement over the conventional one-dimensional approach. The method incorporates a digital impedance filter resulting in multidimensional formulation. Reflecting sound waves approximate the theoretical reflectance for any value of wall impedance and angle of incidence, especially at low frequencies. Both phase and amplitude are preserved. Results obtained from numerical experiments confirm the validity of the approach.

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Signal Processing for 3-D Audio

Authors: Rumsey, Francis

[Feature] The field of spatial audio processing continues to generate new research that feeds into commercial entertainment and communication products. In this article we will summarize some recent convention papers dealing with the topics of upmixing, ambience extraction, rendering moving sources, and crosstalk cancellation.

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