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Authors: Staff, AES
[Feature Article] This article reviews papers and workshops from the recent AES 117th Convention in San Francisco that were concerned with the increasingly important role of networking and software-based systems. In audio engineering today we are seeing the decline of equipment dedicated solely to audio, along with a corresponding rise in the use of generic computing technology adapted for audio-specific purposes.
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Authors: Thiele, Neville
[Feature Article] In the more than 100 years since sound was first recorded in a form that could be replayed, the quality of reproduced sound has improved wonderfully. With digital coding and transmission the frequency response can cover the whole audible spectrum from 5 Hz, or DC if necessary, to 20 kHz, or 40 kHz if needed with 96-kHz sampling. Distortion is limited only by the reproducing loudspeaker, and the dynamic range can be more than 80 dB, though one must be careful in defining it. On the face of things, we can now achieve perfect high-fidelity reproduction.
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Authors: Barbedo, Jayme Garcia Arnal; Lopes, Amauri
The objective assessment of audio quality has made great progress with the introduction of methods based on improved psychoacoustic models. Among these, PEAQ, an ITU standard, deserves special attention. However, the performance of such methods is still poor for a large number of situations. A new cognitive model is proposed that aims at overcoming some of the limitations. The new model extracts a set of parameters from the audio signal which provide high-quality information about the signal. An alternative mapping technique, based on Kohonen self-organizing maps, maps these parameters into an estimate of the subjective quality. The performance of this new approach is compared to that achieved by PEAQ.
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Authors: Ortiz-Berenguer, Luis I.; Casajús-quirós, Francisco J.; Torres-Guijarro, Soledad
[Engineering Reports] The success of polyphonic detection varies depending on the instrument. Different approaches have been proposed. Piano polyphonic detection is particularly difficult. A special approach to detecting piano chords is described. Using a spectral pattern-matching method, chords containing up to four notes have been identified successfully. Chords throughout the complete tonal range (from octave 1 to octave 7) have been tested and identified. Patterns are generated during a training step that uses an acoustical model of a piano.
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Authors: Zielinski, Slawomir K.; Rumsey, Francis; Kassier, Rafael; Bech, Søren
The basic audio quality of 5.1 multichannel audio reproduction was evaluated subjectively under different technical conditions. The resulting database of subjective responses was used to develop a multichannel audio quality expert system. There are three aims of this development: 1) to predict audio quality as a function of individual channel bandwidth; 2) to predict audio quality as a function of selected down-mix algorithms; and 3) to find the optimum band-limitation algorithm or down-mix algorithm for a given total transmission bandwidth of a multichannel audio signal. Results indicate a close correspondence between predicted and actual quality ratings. It is intended that the final version of the quality expert system will be suitable as a decision-making aid for broadcasters and codec designers.
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Authors: Van Wijngaarden, Sander J.; Bronkhorst, Adelbert W.; Boer, Louis C.
[Engineering Reports] Auditory evacuation beacons can be used to guide people to safe exits, even when vision is totally obscured by smoke. Conventional beacons make use of modulated noise signals. Controlled evacuation experiments show that such signals require explicit instructions and are often misunderstood. A new signal was designed that combines a chime sound with a spoken message (“exit here”). In a tunnel environment the evacuation success rate without prior instructions to the participants was 16% for conventional beacons and 87% for the newly designed beacons. Also, a novel way for coding the relative distance to the exit was used. By exploiting the precedence effect through the application of time delays, subjects were induced to naturally “follow” the sound. During an experiment in the mockup of a ship’s interior 88% of participants followed the intended route compared to 38% with the conventional approach. The optimum time delay between beacons was found to be approximately 20 ms.
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