Download Microphone Interference Reduction in Live Sound
When multiple microphones are used to reproduce multiple sources microphone interference, or bleed, can occur due to each microphone picking up more than one source. This paper proposes combining the crosstalk resistant adaptive noise canceller (CTRANC) algorithm with centred adaptive filters using an estimation of delay to suppress the interference, while making little change to the target signal. The proposed method is compared with similar methods in both the anechoic and echoic cases. The method is shown to outperform the other methods in the anechoic case while in the echoic case it is shown to perform less well at reducing the level of the interference but still introduces the least artefacts. Extension to the proposed method to the N source and microphone case is also discussed.
Download The Image-Source Reverberation Model in an N-Dimensional Space
The image method is generalized to geometries with an arbitrary number of spatial dimensions. n-dimensional (n-D) acoustics is discussed, and an algorithm for n-D room impulse response calculations is presented. Synthesized room impulse responses (RIRs) from n-D rooms are presented. RIR characteristics are discussed, and computational considerations are examined.
Download Computationally Efficient Hammond Organ Synthesis
The Hammond organ is an early electronic musical instrument, which was popular in the 1960s and 1970s. This paper proposes computationally efficient models for the Hammond organ and its rotating speaker system, the Leslie. Organ tones are generated using additive synthesis with appropriate features, such as a typical fast attack and decay envelope for the weighted sum of the harmonics and a small amplitude modulation simulating the construction inaccuracies of tone wheels. The key click is realized by adding the sixth harmonic modulated by an additional envelope to the original organ tone. For the Leslie speaker modeling we propose a new approach, which is based on time-varying spectral delay filters producing the Doppler effect. The resulting virtual organ, which is conceptually easy, has a pleasing sound and is computationally efficient to implement.
Download Structured sparsity for audio signals
Regression problems with mixed-norm priors on time-frequency coefficients lead to structured, sparse representations of audio signals. In this contribution, a systematic formulation of thresholding operators that allow for weighting in the time-frequency domain is presented. The related iterative algorithms are then evaluated on synthetic and real-life audio signals in the context of denoising and multi-layer decomposition. Further, initial results on the influence of the shape of the weighting masks are presented.
Download Modeling of the Carbon Microphone Nonlinearity for a Vintage Telephone Sound Effect
The telephone sound effect is widely used in music, television and the film industry. This paper presents a digital model of the carbon microphone nonlinearity which can be used to produce a vintage telephone sound effect. The model is constructed based on measurements taken from a real carbon microphone. The proposed model is a modified version of the sandwich model previously used for nonlinear telephone handset modeling. Each distortion component can be modeled individually based on the desired features. The computational efficiency can be increased by lumping the spectral processing of the individual distortion components together. The model incorporates a filtered noise source to model the self-induced noise generated by the carbon microphones. The model has also an input level depended noise generator for additional sound quality degradation. The proposed model can be used in various ways in the digital modeling of the vintage telephone sound.
Download Physical Modelling of a Wah-wah Effect Pedal as a Case Study for Application of the Nodal DK Method to Circuits with Variable Parts
The nodal DK method is a systematic way to derive a non-linear state-space system as a physical model for an electrical circuit. Unfortunately, calculating the system coefficients requires inversion of a relatively large matrix. This becomes a problem when the system changes over time, requiring continuous recomputation of the coefficients. In this paper, we present an extension of the DK method to more efficiently handle variable circuit elements. The method is exemplified with the Dunlop Crybaby wah-wah effect pedal, as the continuous change of the potentiometer position is an extremely important aspect of the wah-wah effect.
Download Automated Calibration of a Parametric Spring Reverb Model
The calibration of a digital spring reverberator model is crucial for the authenticity and quality of the sound produced by the model. In this paper, an automated calibration of the model parameters is proposed, by analysing the spectrogram, the energy decay curve, the spectrum, and the autocorrelation of the time signal and spectrogram. A visual inspection of the spectrograms as well as a comparison of sound samples proves the approach to be successful for estimating the parameters of reverberators with one, two and three springs. This indicates that the proposed method is a viable alternative to manual calibration of spring reverberator models.
Download Lyapunov Stability Analysis of the Moog Ladder Filter and Dissipativity Aspects in Numerical Solutions
This paper investigates the passivity of the Moog Ladder Filter and its simulation. First, the linearized system is analyzed. Results based on the energy stored in the capacitors lead to a stability domain which is available for time-varying control parameters meanwhile it is sub-optimal for time-invariant ones. A second storage function is proposed, from which the largest stability domain is recovered for a time-invariant Q-parameter. Sufficient conditions for stability are given. Second, the study is adapted to the nonlinear case by introducing a third storage function. Then, a simulation based on the standard bilinear transform is derived and the dissipativity of this numerical version is examined. Simulations show that passivity is not unconditionally guaranteed, but mostly fulfilled, and that typical behaviours of the Moog filter, including self-oscillations, are properly reproduced.
Download A Preliminary Study on Sound Delivery Methods for Footstep Sounds
In this paper, we describe a sound delivery method for footstep sounds, investigating whether subjects prefer static rendering versus dynamic. In this case, dynamic means that the sound delivery method simulates footsteps following the subject. An experiment was run in order to assess subjects’ preferences regarding the sound delivery methods. Results show that static rendering is not significantly preferred to dynamic rendering, but subjects disliked rendering where footstep sounds followed a trajectory different from the one they were walking along.
Download Simulation of a Vacuum-Tube Push-Pull Guitar Power Amplifier
Power ampliﬁers play an important role in producing of guitar sound. Therefore, the modeling of guitar ampliﬁers must also include a power ampliﬁer. In this paper, a push-pull guitar tube power ampliﬁer, including an output transformer and inﬂuence of a loudspeaker, is simulated in different levels of complexity in order to ﬁnd a simpliﬁed model of an ampliﬁer with regards to accuracy and computational efﬁciency.