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Journal of the Audio Engineering Society
The Journal of the Audio Engineering Society — the official publication of the AES — is the only peer-reviewed journal devoted exclusively to audio technology. Published 10 times each year, it is available to all AES members and subscribers.
The Journal contains state-of-the-art technical papers and engineering reports; feature articles covering timely topics; pre and post reports of AES conventions and other society activities; news from AES sections around the world; Standards and Education Committee work; membership news, patents, new products, and newsworthy developments in the field of audio.
2014 November - Volume 62 Number 11
The Influence of Stereoscopy on the Sound Mixing of Movies: A Study on the Front/Rear Balance of Ambience
There is a range of opinions in the cinema industry about the appropriate influence of stereoscopy on the sound mixing for movies. The present study focuses on the perception of ambience. Eight sequences—in their stereoscopic and nonstereoscopic versions, with several different sound mixes—were presented to 44 subjects. For each presentation, subjects had to judge to what extent the mix sounded frontal or “surround.” The goal was to verify whether stereoscopy had an influence on the perception of the front/rear balance of ambience. Results showed that this influence was weak, which was consistent with a preliminary experiment conducted in a mixing auditorium where subjects had to mix the front/rear balance of several sequences themselves.
For the evaluation of perceived quality in audio coding, two well-known subjective test methods, both of which are based on Basic Audio Quality (BAQ), are recommended by the International Telecommunication Union. Although a predictor of quality, BAQ is likely to be multidimensional. Listening tests can be used to evaluate other attributes that contribute to impairments created by coding. The goal of this study is to define categories of additional attributes, thereby providing a complement to the single BAQ metric. When quality attributes are sorted, there appears to be three groups: one related to space, a second related to defects, and a third split into timbre and quality.
A Computationally-Efficient and Perceptually-Plausible Algorithm for Binaural Room Impulse Response Simulation
Simulating the reverberation of rooms has numerous applications that range from evaluating acoustic scenarios in the development of signal processing algorithms to the exploration of speech intelligibility in virtual rooms with movable sources. A hybrid approach was created to simulate room acoustics, achieving high computational efficiency and perceptual plausibility: early reflections were calculated using the image source model (ISM) and the reverberant tail used a feedback delay network (FDN). The FDN approach was modified to be adaptable to various room dimensions and wall absorption coefficients. Using head-related impulse responses, the authors extended it to create spatially-distributed reverberation for arbitrary source and receiver positions. Subjective ratings of the perceived room attributes and the assessment of various common parameters showed a good correspondence between simulated and real rooms.
Because of the intrinsic inefficiency in loudspeakers, most electrical energy is converted into heat with a corresponding rise in temperature of the driver structure. To avoid the harmful effects of elevated temperatures on the voice coil, an active heat control (AHC) process limits the electrical signal when the temperature nears the danger limit. Typical AHC using a closed-loop approach can produce oscillations and audible artifacts because of sensor delays. This paper demonstrates that an open-loop AHC can work. A bounded voice-coil temperature can be achieved using a dynamic range compressor configured as a brick-wall limiter with a threshold that is controlled by the temperature of magnetic components. The temperature of the magnetic assembly and the driving force of the loudspeaker can both be estimated in real-time by a linear quadratic observer (a Kalman filter) and an envelope follower respectively. The new AHC scheme is compared to closed-loop AHC using a simulation example.
Given the effort required to perform subjective tests of quality of service in super-wideband telephone networks, an objective model of perceived degradation was created. This paper describes an efficient classification model of background noise arising at the originating side of super-wideband telephony. Classification depends on the impact on the perceived voice quality at receiving side from originating noises. This approach extends the research findings of narrowband telephony. Subjective experiments showed that background noises can be divided into three relevant classes: environmental noise, breath noise, and crackling noise. Each of these corresponds respectively to spectral flow, acoustic power variations, and the noise spectral centroid. Based on three quality degradation indicators, tests showed 82% correct classification of unknown noise signals.
Standards and Information Documents
AES Standards Committee News
Networked audio interoperability; audio connectors; audio applications of networks
55th Conference Report, Helsinki
56th Conference Preview, London
Despite the intense academic interest in binaural audio over many tens of years, it has only gradually found its way into the mainstream of commercial audio systems. It is still relatively under-used, despite the fact that the majority of listening is now done on headphones. Papers presented at the 55th Conference suggest that we may be getting to a point where binaural technology can be applied more widely.
The differences between conventional voltage-drive amplifiers and current- drive amplifiers are explained using ideal amplifiers. Examples are then given of the use of freely-available integrated audio-amplifier part, used with induction-type hearing loops in current-drive configurations.
Within both the SMPTE and the AES, committees are currently studying the question of the drafting of new standards for the calibration of dubbing theaters and cinemas. The current process has evolved with the changing technology since the introduction of the X-curve in the 1970s, often in an empirical way, but solid, documented explanation of the changes has been lacking. Indeed, even the premises upon which the initial concepts were based have since been called into question. As a?result, myths have often been mixed with facts and incorrectly propagated as truths.
58th Conference, Aalborg, Call for Papers