Journal of the Audio Engineering Society

2006 April - Volume 54 Number 4


Signal-processing algorithms that are meant to evoke a certain subjective effect often have to be perceptually equalized so that any unwanted artifacts are, as far as possible, eliminated. They can then be said to exhibit “unidimensionality of perceived variation.” Aiming to design a method that allows unidimensionality of perceived variation to be verified, established sensory evaluation approaches are examined in terms of their suitability for detailed, undistorted profiling and hence reliable validation of an algorithm’s subjective effects. It is found that a procedure combining multidimensional scaling with supplementary verbal elicitation constitutes the most appropriate approach. In the context of validating a signal-processing method intended to produce a specific spatial effect, this procedure is evaluated and some shortcomings are identified. However, following refinements, it is concluded that these can be overcome through additional data collection and analysis, resulting in a multistage hybrid validation technique.

Spatially Modulated Auditory Alerts for Aviation

Authors: Begault, Durand R.; Anderson, Mark R.; Mcclain, Mryan U.

The technique of spatially modulating an existing or newly created auditory alert along a virtual trajectory to improve its detection in a noisy environment is described. Threshold data from 14 participants were gathered as a function of the spatial modulation rate (0, 1.6, and 3.3 Hz) of an avionics “wind sheer” alert (two successive 300-ms square waves) against a steady-state background noise (Boeing 737-300 flight deck ambient sound). The 70.7% detection threshold for the spatially modulated alert was on average 7.8 dB lower than that for an alert without spatial modulation, with noise and signal both presented over headphones using virtual simulation techniques. The threshold for a headphone-delivered spatially modulated alert was 13.4 dB lower than that for a nonmodulated alert delivered over a single loudspeaker.

[Engineering Reports] A system is described that combines virtual imaging by binaural synthesis and reproduction over loudspeakers using a dynamic head-tracked crosstalk cancellation (CTC) for the listener who is interacting with a common visual virtual reality (VR) application in real time. To provide a full 360° rotation for the listener, the two-loudspeaker dynamic CTC solution was expanded to four channels. This acoustical system is designed for integration into a visual VR system that produces holographic video images and enables the generation of congruent visual and acoustical scenes.

Model Optimization of Distributed-Mode Loudspeaker Using Attached Masses

Authors: Zhang, Suzhen; Shen, Yong; Shen, Xiaoxiang; Zhou, Jinglei

[Engineering Reports] The model of a panel with attached masses is developed and the modes of a distributedmode loudspeaker (DML) are analyzed with FEMLAB. The aim was to make minor modifications to the panel with properly attached masses which will be sufficient to improve its sound pressure response in a given frequency band. Based on the established model, a series of optimized positions of various attached masses is presented using genetic algorithm (GA). The corresponding sound pressure responses are also calculated using the FEMLAB. The attached-masses method (AMM) is verified by experimental investigations. The measurement results indicate that the AMM indeed improves the performance of the DMA with regard to its sound pressure response.

Audio Power Amplification

Authors: Staff, AES

[Feature Article] To many people, power amplifiers are seen as a necessary but rather uninspiring part of the audio signal chain—black (or perhaps silver) boxes that make small signals bigger. Nothing should be simpler, one might think. Until recently amplifier technology had remained relatively unchanged for many years, with any advances involving what was really a number of variations on a theme. For a long time there had been no fundamental paradigm shift in the way in which amplifiers make small signals bigger. Now, however, a quiet revolution is taking place.

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