Journal of the Audio Engineering Society

2002 January/February - Volume 50 Number 1/2

Papers


Audible alarms are ubiguitous and inform us of such things as machine actions, communication, or danger. In this article we focus on smoke detectors, which, while very audible to a normal ear, are poorly suited to people with moderate hearing impairment. This is confirmed by some representative audiometer data. In addition, the measured sound attenuation through walls in normal homes is quite severe at the alarm frequency. Suggestions are made to make audible alarms more effective for the hearing impaired.

Correction to `Multitone Testing of Sound System Components - Some Results and Conclusions, Part 1: History and Theory`

Authors: Czerwinski, Eugene; Voishvillo, Alexander; Alexandrov, Sergei; Terekhov, Alexander

Not available.

Localization of Virtual Sound as a Function of Head-Related Impulse Response Duration

Authors: Senova, Melis A.; McAnally, Ken I.; Martin, Russell L.

The effect of the duration of head-related impulse responses (HRIRs) on the localization of virtual sound was examined. The accuracy with which three participants could localize virtual and free-field sound was measured using an absolute localization paradigm incorporating 354 possible sound-source locations. HRIRs were truncated to durations ranging from 0.32 to 20.48 ms. The truncation of HRIRs results in a smoothing of their frequency-domain representations, which are known as head-related transfer functions (HRTFs). Whereas some previous studies have suggested that the localization of virtual sound is affected only by extreme smoothing of HRTFs, this study indicates that localization can be subtly disrupted by modest HRTF smoothing. For all participants in the study, the localization performance for virtual sound generated from 10.24- and 20.48-ms HRIRs was as good as that for free-field sound. Localization performance gradually decreased as the HRIR duration was reduced, and first became significantly worse than that for free-field sound at HRIR durations ranging from 0.32 to 5.12 ms. Like previous studies, the present study found that the localization performance for virtual sound was not disrupted dramatically until the HRIR duration was reduced to 0.64 or 0.32 ms.

Wavetable Matching of Inharmonic String Tones

Authors: So, Clifford; Horner, Andrew B.

Most previous work on resynthesizing musical instrument tones with wavetable synthesis has assumed that the original tone was harmonic or nearly harmonic. This assumption does not hold for plucked string tones and bowed string tones with vibrato. A wavetable matching technique for inharmonic string tones is introduced. The technique separates partials into different classes based on their degree of inharmonicity, and uses wavetable matching for each class. Results are given for bowed violin and cello (both with vibrato), plucked Chinese pipa, and nonvibrato trumpet tones. The results indicate that the number of wavetables allocated to each class should be about 25-33% of the total number of partials in the class to achieve a good spectral match and adequate frequency deviation resolution. Listening tests have found that the new method improves the perceived match on inharmonic string tones significantly, but results in degradation on the harmonic trumpet tone compared to simple wavetable matching. This suggests that the new method is best for matching plucked string and bowed string tones with vibrato.

Maximizing Performance from Loudspeaker Ports

Authors: Salvatti, Alex; Devantier, Allan; Button, Douglas J.

There is a current trend in the marketplace for loudspeaker ports to have a more aerodynamic appearance. While this may be as much for appearance as for performance reasons, the sharp discontinuity at the end of a traditional port does create turbulence which negatively affects most performance parameters. Ports altered to provide a more aerodynamic shape to minimize turbulence for both the inlet and the exit air streams show performance improvements in efficiency, acoustic compression, maximum output, and distortion reduction. The ideal port shapes for high-velocity inlet and exit air streams are different, and the best solution is one that balances both. In addition turbulence is actually preferred in matters of cooling the box through heat exchange via the air in the port.

Fourth-Order Symmetrical Band-Pass Loudspeaker Systems

Authors: Matusiak, Grzegorz P.; Dobrucki, Andrzej

The theory of band-pass loudspeaker systems is discussed. A reactance transformation method is presented by means of which the Thiele/Small theory of high-pass systems can be applied to the design of band-pass systems. Because the reactance transformation is symmetrical, band-pass systems based on this theory are also symmetrical. The theory of a fourth-order band-pass loudspeaker system derived by applying the reactance transformation to a second-order high-pass system is also included. Higher order band-pass loudspeaker systems are the subject of additional studies in preparation by the authors.

Engineering reports


Wavetable Matching of Inharmonic String Tones

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Localization of Virtual Sound as a Function of Head-Related Impulse Response Duration

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Corrections


Correction to "Multitone Testing of Sound System Components-Some Results and Conclusions, Part 1: History and Theory"

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Standards and Information Documents


AES Standards Committee News

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Features


Audible Alarms for the Hearing Impaired

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Education News

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113th Convention, Los Angeles, Call for Papers

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Departments


News of the Sections

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Upcoming Meetings

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Sound Track

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New Products and Developments

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Available Literature

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Membership Information

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Advertiser Internet Directory

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In Memoriam

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AES Special Publications

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Sections Contacts Directory

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AES Conventions and Conferences

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Extras


Cover and Sustaining Members List

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VIP List

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Editorial Staff

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