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Journal of the AES

2004 June - Volume 52 Number 6

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Efficient Generation of Multichannel Dither Signals (PDF-188K)  
Robert A. Wannamaker    579
When a dither source is needed for multichannel quantization, efficient techniques reduce the computational burden of computing each channel independently. By using appropriate matrix transformations, a single rectangular probability density function (RPDF) random number per sample per channel can be used to produce independent identically distributed (iid) triangular probability density function (TPDF) dither for each channel. After quantization, the errors in each channel are uncorrelated with one another and each has an input-independent mean and variance.  
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Time-Quantized Frequency Modulation, Time-Domain Dither, Dispersive Codes and Parametrically Controlled Noise Shaping in SDM (PDF-1.7MB)  
M. O. J. Hawksford    587
Comparing sigma-delta modulator (SDM) performance to a mathematically equivalent coding technique based on linear frequency modulation (LFM) and time-domain quantization provides additional insight into the noise behavior of SDM. Normally if the conclusions drawn from studies of linear quantization and triangular dither are applied to SDM, then the two-level quantizer range is violated and instability results. Nevertheless, the chaotic-like loop behavior of high-order SDM even with apparent suboptimal dither demonstrates low correlation distortion and is shown here to be insensitive to dither statistics. The LFM model applies ditherin the time domain rather than the amplitude domain and does not violate these assumptions.  
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Augmented Reality Audio for Mobile and Wearable Appliances (PDF-700K)  
Aki Härmä, Julia Jakka, Miikka Tikander, Matti Karjalainen, Tapio Lokki, Jarmo Hiipakka, and Gaëtan Lorho    618
In a portable device, integrating environmental sounds with synthetically generated audio leads to the concept of a wearable device that produces augmented reality. Listeners wear a headset configuration that includes a binaural microphone and stereophonic headphones. In addition to feeding sounds of the environment to the headphones, an auxiliary input provides the means for reproducing recorded audio in a virtual space. Listening tests with a prototype system showed that some experienced listeners found it difficult to distinguish between real and virtual sources.  
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Room Sizing and Optimization at Low Frequencies (PDF-575K)  
Trevor J. Cox, Peter D'Antonio, and Mark R. Avis    640
In critical listening environments, the modes in a room of low volume produce an uneven frequency response and extended decay rates at low frequencies. Using a cost metric based on minimizing the deviations from the flattest possible modal response, the authors propose a new method for choosing the appropriate dimensions for a room of a given volume. While there is a numerically optimum solution, many local minima are equivalent in terms of quality, which then allows for incorporating the physical constraints of real buildings.  
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Comments on "Wavefront Sculpture Technology" (PDF-114K)    652
Chao Jiang and Yong Shen  
Author's Reply (PDF-101K)    653
M. Urban, C. Heil, and P. Bauman  
Correction to "Graphing, Interpretation, and Comparison of Results of Loudspeaker Nonlinear Distortion Measurements" (PDF-21K)    655
A. Voishvillo, A. Terekhov, E. Czerwinski, and S. Alexandrov  
Correction to "Historical Perspectives and Technology Overview of Loudspeakers for Sound Reinforcement" (PDF-21K)    655
J. Eargle and M. Gander  
AES Standards Committee News (PDF-87K)    656
Audio measurements; metadata  
How Loud Is My Broadcast? (PDF-580K)    662
Review of Acoustical Patents (PDF-125K)    659
News of the Sections (PDF-132K)    670
Upcoming Meetings (PDF-50K)    673
Sound Track (PDF-87K)    675
New Products and Developments (PDF-77K)    676
Available Literature (PDF-31K)    678
Membership Information (PDF-85K)    679
Advertiser Internet Directory (PDF-35K)    689
In Memoriam (PDF-35K)    689
Sections Contacts Directory (PDF-65K)    690
AES Conventions and Conferences (PDF-77K)    696
Cover & Sustaining Members List (PDF-352K)    
VIP List & Editorial Staff (PDF-30K)    
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