Download Concatenative Sound Texture Synthesis Methods and Evaluation Concatenative synthesis is a practical approach to sound texture synthesis because of its nature in keeping realistic short-time signal characteristics. In this article, we investigate three concatenative synthesis methods for sound textures: concatenative synthesis with descriptor controls (CSDC), Montage synthesis (MS) and a new method called AudioTexture (AT). The respective algorithms are presented, focusing on the identification and selection of concatenation units. The evaluation demonstrates that the presented algorithms are of close performance in terms of quality and similarity compared to the reference original sounds.
Download The Fender Bassman 5F6-A Family of Preamplifier Circuits—A Wave Digital Filter Case Study The Fender Bassman model 5F6-A was released in 1958 and has become one of the most revered guitar amplifiers of all time. It is the progenitor of a long line of related Fender designs in addition to inspiring Marshall’s first amplifier design. This paper presents a Wave Digital Filter study of the preamplifier circuit of 5F6-Abased amplifiers, utilizing recent theoretical advances to enable the simultaneous simulation of its four nonlinear vacuum tube triodes. The Dempwolf triode model is applied along with an iterative Newton solver to calculate the scattering at the 25 port R-type adapter at the root of the WDF tree. Simulation results are compared to “ground truth” SPICE data showing excellent agreement.
Download Sound Morphing by Audio Descriptors and Parameter Interpolation We present a strategy for static morphing that relies on the sophisticated interpolation of the parameters of the signal model and the independent control of high-level audio features. The source and target signals are decomposed into deterministic, quasi-deterministic and stochastic parts, and are processed separately according to sinusoidal modeling and spectral envelope estimation. We gain further intuitive control over the morphing process by altering the interpolated spectrum according to target values of audio descriptors through an optimization process. The proposed approach leads to convincing morphing results in the case of sustained or percussive, harmonic and inharmonic sounds of possibly different durations.
Download Audio Nonlinear Modeling through Hyperbolic Tangent Functionals In the present contribution we present the preliminary results of a black box nonlinear system (NLS) modeling. The NLS is composed by a nonlinear sigmoid-type input-output relationship (NLTF) followed by a linear system (LTI), as in a Hammerstein nonlinear system. Here, the used NLTF is derived from a deformation of the Hyperbolic Tangent power expansion. The advantage of using the hyperbolic tangent function is that nonlinearity depends on the linear and cubic terms that measure curvature (and thus nonlinearity) of the transfer function. The hyperbolic tangent model is extended to other types of nonlinear systems by expanding the nonlinear system in linear and increasingly nonlinear contributions, where the expansion parameters are deformed to enhance or suppress specific nonlinear modes of the expansion. Simulations were performed using Matlab 2012a. The preliminary results show fairly good agreement between the system obtained by parametric inference and a reference system, with mean square error (MSE)=0.035.
Download Directivity Patterns Controlling the Auditory Source Distance What influence does the directivity of a sound source have on the perceived distance impression in a room? We propose different directivity pattern designs able to modify the auditory source distance. The idea is accompanied with a comprehensive experimental study investigating the audio effect and its behavior by auralization of directional sound source and room using a 24-channel loudspeaker ring inside an anechoic chamber. In addition to the proposed directivity designs, the study covers influence of auralized room, source-to-receiver distance, signal, and single-channel reverberation. Moreover, simple room acoustical measures perform well in predicting the new effect.
Download Time-Variant Gray-Box Modeling of a Phaser Pedal A method to measure the response of a linear time-variant (LTV) audio system is presented. The proposed method uses a series of short chirps generated as the impulse response of several cascaded allpass filters. This test signal can measure the characteristics of an LTV system as a function of time. Results obtained from testing of this method on a guitar phaser pedal are presented. A proof of concept gray-box model of the measured system is produced based on partial knowledge about the internal structure of the pedal and on the spectral analysis of the measured responses. The temporal behavior of the digital model is shown to be very similar to that of the measured device. This demonstrates that it is possible to measure LTV analog audio systems and produce approximate virtual analog models based on these results.
Download Perceptual Audio Source Culling for Virtual Environments Existing game engines and virtual reality software, use various techniques to render spatial audio. One such technique, binaural synthesis, is achieved through the use of head-related transfer functions, in conjunction with artificial reverberators. For virtual environments that embody a large number of concurrent sound sources, binaural synthesis will be computationally costly. The work presented in this paper aims to develop a methodology that improves overall performance by culling inaudible and perceptually less prominent sound sources in order to reduce performance implications. The proposed algorithm is benchmarked and compared with distance-based, volumetric culling methodology. A subjective evaluation of the perceptual performance of the proposed algorithm for acoustic scenes having different compositions is also provided.
Download A Modal Approach to the Numerical Simulation of a String Vibrating Against an Obstacle: Applications to Sound Synthesis A number of musical instruments (electric basses, tanpuras, sitars...) have a particular timbre due to the contact between a vibrating string and an obstacle. In order to simulate the motion of such a string with the purpose of sound synthesis, various technical issues have to be resolved. First, the contact phenomenon, inherently nonlinear and producing high frequency components, must be described in a numerical manner that ensures stability. Second, as a key ingredient for sound perception, a fine-grained frequencydependent description of losses is necessary. In this study, a new conservative scheme based on a modal representation of the displacement is presented, allowing the simulation of a stiff, damped string vibrating against an obstacle with an arbitrary geometry. In this context, damping parameters together with eigenfrequencies of the system can be adjusted individually, allowing for complete control over loss characteristics. Two cases are then numerically investigated: a point obstacle located in the vicinity of the boundary, mimicking the sound of the tanpura, and then a parabolic obstacle for the sound synthesis of the sitar.
Download Resolving Grouped Nonlinearities in Wave Digital Filters using Iterative Techniques In this paper, iterative zero-finding techniques are proposed to resolve groups of nonlinearities occurring in Wave Digital Filters. Two variants of Newton’s method are proposed and their suitability towards solving the grouped nonlinearities is analyzed. The feasibility of the approach with implications for WDFs containing multiple nonlinearities is demonstrated via case studies investigating the mathematical properties and numerical performance of reference circuits containing diodes and transistors; asymmetric and symmetric diode clippers and a common emitter amplifier.
Download Black-box Modeling of Distortion Circuits with Block-Oriented Models This paper describes black-box modeling of distortion circuits. The analyzed distortion circuits all originate from guitar effect pedals, which are widely used to enrich the sound of an electric guitar with harmonics. The proposed method employs a blockoriented model which consists of a linear block (filter) and a nonlinear block. In this study the nonlinear block is represented by an extended parametric input/output mapping function. Three distortion circuits with different nonlinear elements are analyzed and modeled. The linear and nonlinear parts of the circuit are analyzed and modeled separately. The Levenberg–Marquardt algorithm is used for iterative optimization of the nonlinear parts of the circuits. Some circuits could not be modeled with high accuracy, but the proposed model has shown to be a versatile and flexible tool when modeling distortion circuits.