Journal of the Audio Engineering Society

2003 June - Volume 51 Number 6


[feature article] “Audio engineers, don’t live in the past. Take advantage of the demand for content stimulated by new media!” This was the message of a fascinating workshop at the AES 113th Convention, held last October in Los Angeles. This panel of experts was chaired by Dave Davis of QCA Mastering; Davis is also a lecturer at the University of Cincinnati. The panel provided evidence of their own experience in trying to make money out of professional audio in the face of changing markets: Bob Ludwig, of Gateway Mastering and DVD, has undertaken pioneering work in mastering for DVD, SACD, and advanced media; Bill McQuay has been associated for many years with Radio Expeditions, a collaboration between National Public Radio and the National Geographic Society; Bobby Owsinski of Surround Associates has worked on numerous surround productions for DVD; and Mike Sokol, JMS Productions & Fits and Starts Productions, has a diversified business including surround sound effects for radio drama and surround sound for Power- Point presentations.

Automotive Audio

Authors: Francis Rumsey

[feature article] The AES has been actively promoting the topic of automotive audio in recent years, through the activities of the Technical Council and through a range of papers and workshops specializing in this important field. Now that many people spend more time listening to music in their cars than they do in their living rooms, and considering that the interiors of vehicles now have the potential to house a truck load of multimedia devices, R&D organizations around the world have budgeted increased funds to improve the sound quality engineering of these environments. In this article some themes from recent works are brought together and developed.

History of Spatial Coding

Authors: Davis, Mark F.

[feature article] The goal of spatial audio coding and reproduction is to convey some measure of the dimensional aspects of a sound event to the end listener, preferably in a practical and cost-effective manner. The importance of the spatial aspects of sound has been clear since before the dawn of audio reproduction, as evidenced, for example, in the design of concert halls. So it is not surprising that concern for the accurate capture, transmission, and reproduction of the spatial components of a sound event goes back almost to the birth of the audio industry as we know it today. Yet even now, completely accurate spatial reproduction remains elusive, and is perhaps the largest single imperfection in modern audio technology.

A new algorithm, the tree evolution algorithm (TEA), is proposed for parameter optimization separately in a complex solution space, with its search algorithm forming a tree structure. It is shown that the algorithm, which is based on the genetic annealing algorithm (GAA), is more accurate and more stable than GAA in estimating the optimum parameters for double frequency modulation (DFM) synthesis.

The results of a preliminary investigation into the theoretical evaluation and study of the relationship between some room acoustical descriptors used for the subjective assessment of performance halls are considered. The concern is about three parameters, namely, the interaural cross-correlation coefficient (IACC), the early lateral energy fraction (ELEF) or a related measure, the spaciousness S, and the initial time-delay gap (ITDG). To this end, the impulse response (IR) for a hard rectangular room with a side balcony on each lateral wall is calculated. This room configuration is considered a coarse approximation of a small performance hall. The theoretical model used for this calculation represents a combination of the image sources method for the wave reflections at the hard surfaces and an exact model accounting for the diffraction of waves at the wedges of the balconies, the latter being even extended to the second order of multiple diffractions. Furthermore, and in view of a more realistic determination of the IACC, the thus obtained impulse response is convolved with the head-related transfer function (HRTF) for both ears as measured using a dummy head (KEMAR) in an anechoic environment. In this respect the directional characteristics of the different components of the impulse response are accounted for in the IACC, but to a lesser degree than in the ELEF, whereas the ITDG is independent of direction. It is found that simple relations may be established between these parameters, which may be useful for room acoustical assessments or for estimating one of these parameters, when inaccessible, by knowing the value of any of the other ones.

An Efficient Algorithm for the Restoration of Audio Signals Corrupted with Low-Frequency Pulses

Authors: Esquef, Paulo A. A.; Biscainho, Luiz W. P.; Välimäki, Vesa

Digital audio restoration of old recordings is addressed, with a focus on the removal of long pulses with low-frequency content. The main drawback of the state-of-the-art method, which is based on the separation of autoregressive (AR) processes, is its high computational complexity. A method is proposed in which the pulse tails are first estimated via a nonlinear scheme called two-pass split-window (TPSW) filtering, followed by a polynominal smoothing stage. After removing the tail of each pulse by subtraction, the remaining initial clicks are suppressed through a model-based declicking algorithm. The proposed procedure is as effective for pulse removal as the AR-based method but has a substantially lower computational complexity. Moreover, from a user point of view, its processing parameters are more intuitive and easier to adjust.

The subjective effects of controlled limitation of audio bandwidth on the assessment of audio quality were studied. The investigation was focused on the standard 5.1 multichannel audio setup and limited to the optimum listening position. The effect of video presence on the audio quality assessment was also investigated. The results of formal subjective tests indicate that it is possible to limit the bandwidth of the center or the rear channels without significant deterioration of the audio quality for most program material types investigated. Video presence had a small effect on the audio quality assessment.

Engineering reports

Study on the Relationship between Some Room Acoustical Descriptors

Automated Parameter Optimization for Double Frequency Modulation Synthesis Using a Tree Evolution Algorithm

Standards and Information Documents

AES Standards Committee News


History of Spatial Coding   Mark F. Davis

Automotive Audio

New Media for Music: An Adaptive Response to Technology

Updates and Corrections to the 2002/2003 International Sections Directory

Education News

116th Convention, Berlin, Call for Papers


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