Download Harmonic Mixing Based on Roughness and Pitch Commonality The practice of harmonic mixing is a technique used by DJs for the beat-synchronous and harmonic alignment of two or more pieces of music. In this paper, we present a new harmonic mixing method based on psychoacoustic principles. Unlike existing commercial DJ-mixing software which determine compatible matches between songs via key estimation and harmonic relationships in the circle of fifths, our approach is built around the measurement of musical consonance at the signal level. Given two tracks, we first extract a set of partials using a sinusoidal model and average this information over sixteenth note temporal frames. Then within each frame, we measure the consonance between all combinations of dyads according to psychoacoustic models of roughness and pitch commonality. By scaling the partials of one track over ± 6 semitones (in 1/8th semitone steps), we can determine the optimal pitch-shift which maximises the consonance of the resulting mix. Results of a listening test show that the most consonant alignments generated by our method were preferred to those suggested by an existing commercial DJ-mixing system.
Download Numerical Simulation of Spring Reverberation Virtual analog modeling of spring reverberation presents a challenging problem to the algorithm designer, regardless of the particular strategy employed. The difficulties lie in the behaviour of the helical spring, which, due to its inherent curvature, shows characteristics of both coherent and dispersive wave propagation. Though it is possible to emulate such effects in an efficient manner using audio signal processing constructs such as delay lines (for coherent wave propagation) and chains of allpass filters (for dispersive wave propagation), another approach is to make use of direct numerical simulation techniques, such as the finite difference time domain method (FDTD) in order to solve the equations of motion directly. Such an approach, though more computationally intensive, allows a closer link with the underlying model system— and yet, there are severe numerical difficulties associated with such designs, and in particular anomalous numerical dispersion, requiring some care at the design stage. In this paper, a complete model of helical spring vibration is presented; dispersion analysis from an audio perspective allows for model simplification. A detailed description of novel FDTD designs follows, with special attention is paid to issues such as numerical stability, loss modeling, numerical boundary conditions, and computational complexity. Simulation results are presented.
Download Neural-Driven Multi-Band Processing for Automatic Equalization and Style Transfer We present a Neural-Driven Multi-Band Processor (NDMP), a differentiable audio processing framework that augments a static sixband Parametric Equalizer (PEQ) with per-band dynamic range
compression. We optimize this processor using neural inference
for two tasks: Automatic Equalization (AutoEQ), which estimates
tonal and dynamic corrections without a reference, and Production
Style Transfer (NDMP-ST), which adapts the processing of an input signal to match the tonal and dynamic characteristics of a reference. We train NDMP using a self-supervised strategy, where the
model learns to recover a clean signal from inputs degraded with
randomly sampled NDMP parameters and gain adjustments. This
setup eliminates the need for paired input–target data and enables
end-to-end training with audio-domain loss functions. In the inference, AutoEQ enhances previously unseen inputs in a blind setting, while NDMP-ST performs style transfer by predicting taskspecific processing parameters. We evaluate our approach on the
MUSDB18 dataset using both objective metrics (e.g., SI-SDR,
PESQ, STFT loss) and a listening test.
Our results show that
NDMP consistently outperforms traditional PEQ and a PEQ+DRC
(single-band) baseline, offering a robust neural framework for audio enhancement that combines learned spectral and dynamic control.
Download Effect of augmented audification on perception of higher statistical moments in noise Augmented audification has recently been introduced as a method that blends between audification and an auditory graph. Advantages of both standard methods of sonification are preserved. The effectivity of the method is shown in this paper by the example of random time series. Just noticeable kurtosis differences are effected positively by the new method as compared to pure audification. Furthermore, skewness can be made audible.
Download Efficient finite-difference room acoustics simulation incorporating extended-reacting elements A method is proposed that allows finite-difference (FD) simulation of room acoustics to incorporate extended-reacting porous elements without adding major computational cost. The porous elements are described by a rigid-frame equivalent fluid model and are incorporated into the time-domain formulation through auxiliary differential equations. By using a local staggered grid scheme for the boundaries of the porous elements, the method allows an efficient second-order scalar approach to be used for the uniform air and porous element interior regions that make up the majority of the computational domain. Both the scalar and staggered schemes are based on a face-centered cubic grid to minimize numerical dispersion. A software implementation running on GPU shows the accuracy of the method compared to a theoretical reference, and demonstrates the method’s computational efficiency through a benchmark example.
Download Self-Organised Sounds with a Tremolo Oscillator Tremolo is usually regarded as belonging to the domain of note embellishments. Rapid tremolo, taken into the audio range, is an interesting synthesis technique which is related to FM and granular synthesis. We present a tremolo oscillator, capable of a wide range of sonorities, and illustrate some of its capabilities in applications such as feature-based synthesis and sonification. A reference implementation in Csound is given. The tremolo oscillator is then put into a feedback system, where its output is subject to feature extraction, and the extracted features in turn are mapped to its control parameters. Chaotic orbits in this feedback system guarantee continuous variation, in contrast to the trivial periodic patterns that are easily obtained.
Download Iterative Structured Shrinkage Algorithms for Stationary/Transient Audio Separation In this paper, we present novel strategies for stationary/transient signal separation in audio signals in order to exploit the basic observation that stationary components are sparse in frequency and persistent over time whereas transients are sparse in time and persistent across frequency. We utilize a multi-resolution STFT approach which allows to define structured shrinkage operators to tune into the characteristic spectrotemporal shapes of the stationary and transient signal layers. Structure is incorporated by considering the energy of time-frequency neighbourhoods or modulation spectrum regions instead of individual STFT coefficients, and shrinkage operators are employed in a dual-layered Iterated Shrinkage/Thresholding Algorithm (ISTA) framework. We further propose a novel iterative scheme, Iterative Cross-Shrinkage (ICS). In experiments using artificial test signals, ICS clearly outperforms the dual-layered ISTA and yields particularly good results in conjunction with a dynamic update of the shrinkage thresholds. The application of the novel algorithms to recordings from acoustic musical instruments provides perceptually convincing separation of transients.
Download Wave Field Synthesis - A Promising Spatial Rendering Concept Modern convolution technologies offer possibilities to overcome principle shortcomings of loudspeaker stereophony by exploiting the Wave Field Synthesis (WFS) concept for rendering virtual spatial characteristics of sound events. Based on the Huygens principle loudspeaker arrays are reproducing a synthetic sound field around the listener, whereby the dry audio signal is combined with measured or modelled information about the room and the source’s position to enable the accurate reproduction of the source within its acoustical environment. Not surprisingly, basic and practical constraints of WFS systems limit the rendering accurateness and the perceived spatial audio quality to a certain degree, dependent on characteristic features and technical parameters of the sound field synthesis. However, recent developments have shown already that a number of applications could be possible in the near future. An attractive example is the synthesis of WFS and stereophony offering enhanced freedom in sound design as well as improved quality and more flexibility in practical playback situations for multichannel sound mixes.
Download FAST MUSIC – An Efficient Implementation Of The Music Algorithm For Frequency Estimation Of Approximately Periodic Signals Noise subspace methods are popular for estimating the parameters of complex sinusoids in the presence of uncorrelated noise and have applications in musical instrument modeling and microphone array processing. One such algorithm, MUSIC (Multiple Signal Classification) has been popular for its ability to resolve closely spaced sinusoids. However, the computational efficiency of MUSIC is relatively low, since it requires an explicit eigenvalue decomposition of an autocorrelation matrix, followed by a linear search over a large space. In this paper, we discuss methods for and the benefits of converting the Toeplitz structure of the autocorrelation matrix to circulant form, so that eigenvalue decomposition can be replaced by a Fast Fourier Transform (FFT) of one row of the matrix. This transformation requires modeling the signal as at least approximately periodic over some duration. For these periodic signals, the pseudospectrum calculation becomes trivial and the accuracy of the frequency estimates only depends on how well periodicity detection works. We derive a closed-form expression for the pseudospectrum, yielding large savings in computation time. We test our algorithm to resolve closely spaced piano partials.
Download A Quaternion-Phase Oscillator An approach to designing dynamical systems with a three-dimensional state space is described that can be used to build a variety of non-periodic oscillators. The state space is taken to be a 3sphere, which is identified with the manifold of unit quaternions. Any such system can be described as a quaternion-valued ordinary differential equation, which is digitally realized using an approximation as a finite difference e quation. Two examples are shown. Compared to previous applications of dynamical systems used to generate audio samples, the approach described here offers a wide choice of specific flows which can neither diverge nor approach a stable limit point.