AES Budapest 2012
Paper Session P3
P3 - Music and Modeling
Thursday, April 26, 11:00 — 12:30 (Room: Lehar)
P3-1 Physical Model of the Slide Guitar: An Approach Based on Contact Forces—Gianpaolo Evangelista, Linköping University - Campus Norrköping, Sweden
In this paper we approach the synthesis of the slide guitar, which is a particular play mode of the guitar where continuous tuning of the tones is achieved by sliding a metal or glass piece, the bottleneck, along the strings on the guitar neck side. The bottleneck constitutes a unilateral constraint for the string vibration. Dynamics is subject to friction, scraping, textured displacement, and collisions. The presented model is physically inspired and is based on a dynamic model of friction, together with a geometrical model of the textured displacements and a model for collisions of the string with the bottleneck. These models are suitable for implementation in a digital waveguide computational scheme for the 3-D vibration of the string, where continuous pitch bending is achieved by all-pass filters to approximate fractional delays. Friction is captured by nonlinear state-space systems in the slide junction and textured displacements by signal injection at a variable point in the waveguide.
Convention Paper 8590 (Purchase now)
P3-2 Measuring Spectral Directivity of an Electric Guitar Amplifier—Agnieszka Roginska, New York University - New York, NY, USA; Alex U. Case, University of Massachusetts Lowell - Lowell, MA, USA; Andrew Madden, Jim Anderson, New York University - New York, NY, USA
The recorded timbre of an electric guitar amplifier is highly dependent on the position of the microphone. Small changes in the location of the microphone can yield significant spectral differences, particularly at positions very close to the amp. This paper presents densely measured radiation pattern characteristics of an electric guitar amplifier on a 3-D grid in front, beside, behind, and above the amplifier in a hemi-anechoic space. We use this data to analyze the change in spectral differences between the numerous points on the measurement grid. Differences between acoustically measured and estimated frequency responses (predicted, using interpolation) are used to study the change in the acoustic field in order to gain insight and an understanding of the spectral directivity sensitivity factor of the electric guitar amplifier.
Convention Paper 8592 (Purchase now)
P3-3 Magnitude-Priority Filter Design for Audio Applications—Balázs Bank, Budapest University of Technology and Economics - Budapest, Hungary
In audio, often specialized filter design methods are used that take into account the logarithmic frequency resolution of hearing. A notable side-effect of these quasi-logarithmic frequency design methods is a high-frequency attenuation for non-minimum-phase targets due to the frequency-dependent windowing effect of the filter design. This paper presents two approaches for the correction of this high-frequency attenuation, based either on the iterative update of the magnitude, or the iterative update of the phase of the target specification. As a result, the filter follows both magnitude and phase in those frequency regions where it can, while where this is not possible, it focuses on the magnitude. Thus, the new method combines the advantages of traditional complex and magnitude-only filter designs. The algorithms are demonstrated by parallel filter designs, but since the method does not make any assumption on the filter design algorithm used in the iteration, it is equally applicable to other techniques.
Convention Paper 8591 (Purchase now)
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