Download Spectral data management tools for additive synthesis This paper describes a set of procedures, named Toolbox, for spectral data reduction to be used in additive synthesis system based on sinusoidal model. The Toolbox has been developed in MATLAB with the specific aim to support the realization of a very large scale additive synthesis system (AddSynth) based on special purpose VLSI chips. Test signals and musical tones played by real acoustic instruments, in different conditions of execution: intensity, pitch etc, are considered. The Toolbox mainly performs spectral envelope data extraction, data reduction, spectral interpolation and produces proper data block set for both the AddSynth machine and the related software simulator.
Download Designing a Library for Generative Audio in Unity This paper overviews URALi, a library designed to add generative sound synthesis capabilities to Unity. This project, in particular, is directed towards audiovisual artists keen on working with algorithmic systems in Unity but can not find native solutions for procedural sound synthesis to pair with their visual and control ones. After overviewing the options available in Unity concerning audio, this paper reports on the functioning and architecture of the library, which is an ongoing project.
Download Time-Variant Delay Effects based on Recurrence Plots Recurrence plots (RPs) are two-dimensional binary matrices used to represent patterns of recurrence in time series data, and are typically used to analyze the behavior of non-linear dynamical systems. In this paper, we propose a method for the generation of time-variant delay effects in which the recurrences in an RP are used to restructure an audio buffer. We describe offline and realtime systems based on this method, and a realtime implementation for the Max/MSP environment in which the user creates an RP graphically. In addition, we discuss the use of gestural data to generate an RP, suggesting a potential extension to the system. The graphical and gestural interfaces can provide an intuitive and convenient way to control a time varying delay.
Download Spectral Dealy Filters with Feedback Delay Filters with Feedback and Time-Varying Coefficients A recently introduced structure to implement a continuously smooth spectral delay, based on a cascade of first-order allpass filters and an equalizing filter, is described and the properties of this spectral delay filter are reviewed. A new amplitude envelope equalizing filter for the spectral delay filter is proposed and the properties of structures utilizing feedback and/or time-varying filter coefficients are discussed. In addition, the stability conditions for the feedback and the time-varying structures are derived. A spectral delay filter can be used for synthesizing chirp-like sounds or for modifying the timbre of arbitrary audio signals. Sound examples on the use of the spectral delay filters utilizing the structures discussed in this paper can be found at http://www.acoustics.hut. fi/publications/papers/dafx09-sdf/.
Download Binaural source localization In binaural signals, interaural time differences (ITDs) and interaural level differences (ILDs) are two of the most important cues for the estimation of source azimuths, i.e. the localization of sources in the horizontal plane. For narrow band signals, according to the duplex theory, ITD is dominant at low frequencies and ILD is dominant at higher frequencies. Based on the STFT spectra of binaural signals, a method is proposed for the combined evaluation of ITD and ILD for each individual spectral coefficient. ITD and ILD are related to the azimuth through lookup models. Azimuth estimates based on ITD are more accurate but ambiguous at higher frequencies due to phase wrapping. The less accurate but unambiguous azimuth estimates based on ILDs are used in order to select the closest candidate azimuth estimates based on ITDs, effectively improving the azimuth estimation. The method corresponds well with the duplex theory and also handles the transition from low to high frequencies gracefully. The relations between the ITD and ILD and the azimuth are computed from a measured set of head related transfer functions (HRTFs), yielding azimuth lookup models. Based on a study of these models for different subjects, parametric azimuth lookup models are proposed. The parameters of these models can be optimized for an individual subject whose HRTFs have been measured. In addition, subject independent lookup models are proposed, parametrized only by the distance between the ears, effectively enabling source localization for subjects whose HRTFs have not been measured.
Download A Digital Model of the Buchla Lowpass-Gate In recent years there has been an increasing amount of interest in the style of synthesis implemented by Don Buchla in his instrument designs from the early 1960s until the present. A key part of the Buchla synthesizer and its characteristic quality is the ’lowpass gate’ filter and the acoustic-like plucked sounds that it provides. In this work we examine the circuit of the low-pass gate, both its audio and control portions. We propose a number of digital models of these circuits, as well as a model of the photoresistive optoisolator or ’vactrol’ used within them. In the case of the audio path of the device, we pay particular attention to maintaining desirable behavior under time-variation of its parameters. The resulting digital model retains much of the interesting character of the analog system, and is computationally cheap enough to use within a standard computer-music setup.
Download Frequency estimation of the first pinna notch in Head-Related Transfer Functions with a linear anthropometric model The relation between anthropometric parameters and Head-Related Transfer Function (HRTF) features, especially those due to the pinna, are not fully understood yet. In this paper we apply signal processing techniques to extract the frequencies of the main pinna notches (known as N1 , N2 , and N3 ) in the frontal part of the median plane and build a model relating them to 13 different anthropometric parameters of the pinna, some of which depend on the elevation angle of the sound source. Results show that while the considered anthropometric parameters are not able to approximate with sufficient accuracy neither the N2 nor the N3 frequency, eight of them are sufficient for modeling the frequency of N1 within a psychoacoustically acceptable margin of error. In particular, distances between the ear canal and the outer helix border are the most important parameters for predicting N1 .
Download Kinematics of Ideal String Vibration Against a Rigid Obstacle This paper presents a kinematic time-stepping modeling approach of the ideal string vibration against a rigid obstacle. The problem is solved in a single vibration polarisation setting, where the string’s displacement is unilaterally constrained. The proposed numerically accurate approach is based on the d’Alembert formula. It is shown that in the presence of the obstacle the lossless string vibrates in two distinct vibration regimes. In the beginning of the nonlinear kinematic interaction between the vibrating string and the obstacle the string motion is aperiodic with constantly evolving spectrum. The duration of the aperiodic regime depends on the obstacle proximity, position, and geometry. During the aperiodic regime the fractional subharmonics related to the obstacle position may be generated. After relatively short-lasting aperiodic vibration the string vibration settles in the periodic regime. The main general effect of the obstacle on the string vibration manifests in the widening of the vibration spectra caused by transfer of fundamental mode energy to upper modes. The results presented in this paper can expand our understanding of timbre evolution of numerous stringed instruments, such as, the guitar, bray harp, tambura, veena, sitar, etc. The possible applications include, e.g., real-time sound synthesis of these instruments.
Download Spatializing Screen Readers: Extending VoiceOver via Head-Tracked Binaural Synthesis for User Interface Accessibility Traditional screen-based graphical user interfaces (GUIs) pose significant accessibility challenges for visually impaired users. This
paper demonstrates how existing GUI elements can be translated
into an interactive auditory domain using high-order Ambisonics and inertial sensor-based head tracking, culminating in a realtime binaural rendering over headphones. The proposed system
is designed to spatialize the auditory output from VoiceOver, the
built-in macOS screen reader, aiming to foster clearer mental mapping and enhanced navigability.
A between-groups experiment
was conducted to compare standard VoiceOver with the proposed
spatialized version. Non visually-impaired participants (n = 32),
with no visual access to the test interface, completed a list-based
exploration and then attempted to reconstruct the UI solely from
auditory cues. Experimental results indicate that the head-tracked
group achieved a slightly higher accuracy in reconstructing the interface, while user experience assessments showed no significant
differences in self-reported workload or usability. These findings
suggest that potential benefits may come from the integration of
head-tracked binaural audio into mainstream screen-reader workflows, but future investigations involving blind and low-vision users
are needed.
Although the experimental testbed uses a generic
desktop app, our ultimate goal is to tackle the complex visual layouts of music-production software, where an head-tracked audio
approach could benefit visually impaired producers and musicians
navigating plug-in controls.