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P20 - Audio Content: Interpretation and Management
Sunday, October 8, 9:00 am — 12:30 pm
Chair: Mark Sandler, Queen Mary, University of London - London, UK
P20-1 An Experimental Verification of Localization in Two-Channel Stereo—Eric Benjamin, Dolby Laboratories - San Francisco, CA, USA
In two-channel stereo the ratio of intensities between two loudspeakers is varied, and at low frequencies the differences in times-of-arrival of the sounds create phase differences between the two ears. These phase differences mimic those experienced in natural hearing, and thus the perceived localization is similar. The experiments described in this paper test the localization provided by stereo in actual use. The perceptions of listeners were collected and the acoustic signals at the entrance to their ear canals were recorded for analysis. Localization under optimum conditions gave results that are substantially similar to what is predicted by theory. Localization in sub-optimum conditions, such as at very low frequencies and such as are encountered in automobiles, was found to be substantially in error.
Convention Paper 6968 (Purchase now)
P20-2 Solving the Sticky Shed Problem in Magnetic Recording Tapes: New Laboratory Research and Analysis Provide a Safe and Effective Remedy—Charles Richardson, Richardson Audio Video - Annapolis, MD, USA
The goal is to make available to AES’s members new research of its author and a leading analytical laboratory concerning: (a) the primary causes and principal source of sticky shed material found on magnetic tapes; (b) the unnecessary damage which baking tapes causes; and (c) the development of a new, safe and effective process that restores contaminated tapes to their originally anticipated life span and allows repeated, trouble-free playbacks with excellent sonic performance. The methods used were: (a) chemical analysis of tapes’ composition with and without sticky shed, (b) electron microscopic imaging of contaminated and remediated tapes, and (c) stickion-friction measurements of tapes without back coating and free of sticky shed, with back coating and sticky shed, and after restoration. The key findings are: (a) heat and hydrolysis cause sticky shed, (b) back coating is the source of most of the sticky shed, (c) baking causes degraded playback and permanent damage, and (d) correct removal of back coating restores most problem tapes to long life allowing many trouble-free playbacks providing excellent sonic performance.
Convention Paper 6969 (Purchase now)
P20-3 Tape Degradation Factors and Predicting Tape Life—Richard Hess, Vignettes Media - Aurora, Ontario, Canada
From 1947 through the 1990s, most of the world’s sound was entrusted to analog magnetic recording tape for archival storage. Now that analog magnetic tape has moved into a niche market, audio professionals and archivists worry about the remaining lifetime of existing tapes. This paper defines the basic tape types and the current state of knowledge of their degradation mechanisms. Conflicting prior work is reviewed and correlated with current experience. Illustrations of various types of tape degradations and a survey of many of the techniques used for tape restoration are included. Suggestions are made for further research and archival practices.
Convention Paper 6970 (Purchase now)
P20-4 Music Metadata Quality: A Multiyear Case Study Using the Music of Skip James—Adrian Freed, University of California at Berkely - Berkeley, CA, USA
The case study reported here is an exploratory step toward developing a quantitative system for audio and music metadata quality measurement. Errors, their sources, and their propagation mechanisms are carefully examined in a small but meaningful subset of music metadata centered on a single artist Skip James.
Convention Paper 6971 (Purchase now)
P20-5 Stop Counting Samples—Thomas Lund, TC Electronic A/S - Risskov, Denmark
Level restriction in digital music production has traditionally been based on simply measuring the value of individual samples. Where sample counting may have been appropriate in the early days of digital, previous work has revealed how processing now exploits our archaic measurement principles to an extent where significant distortion can be expected to develop downstream of the studio in perceptual codecs, DA, and sample rate converters. This paper suggests that production methods in combination with simplistic level assessment is responsible not only for more distortion and listener fatigue, but also for level jumps where digital interfacing or file transferring is used, e.g., at a broadcast station. Improved working practices and measurement methods are suggested.
Convention Paper 6972 (Purchase now)
P20-6 A Real-Time Rhythmic Analyzer and Equalizer—Jörn Loviscach, Hochschule Bremen (University of Applied Sciences) - Bremen, Germany
The rhythmic analyzer and equalizer presented in this paper allows to cut or boost the signal at a given audio frequency and a given rhythmic frequency, that is, number of beats per minute (BPM). A task that can be addressed with the rhythmic equalizer is, for instance, to emphasize series of 1/8 triplet notes played on the hi-hat of a drum set. The software works in real time and offers an interactive graphical user interface that supports both analysis and adjustment. The current energy distribution in the two-dimensional audio frequency (Hz) / rhythmic frequency (BPM) space is displayed as a continuously updated backdrop image. The user paints the intended adjustments of BPM levels and phases onto an image layer on top of this image.
Convention Paper 6973 (Purchase now)
P20-7 Blind Dereverberation of Audio Signals Using a Modified Constant Modulus Algorithm—Hesu Huang, Chris Kyriakakis, University of Southern California - Los Angeles, CA, USA
The single-channel blind dereverberation approach we present in this paper is an extension to the one based on Constant Modulus Algorithm (CMA) we proposed in previous work. By substituting the modified CMA algorithm for the original CMA algorithm, we demonstrate a more suitable approach for blind deconvolution of reverberant audio signals with super-Gaussian distribution. To further improve the performance, the modified CMA is applied to the LP residual instead of the time domain signal because of the flatter spectrum provided by the Linear Prediction (LP) residual approach. In real implementations, a Delayless Subband Adaptive Filtering (DSAF) architecture is also combined with CMA to further reduce the computational complexity. Experimental results show that our modified method outperforms previous approaches in audio signal blind dereverberation.
Convention Paper 6974 (Purchase now)