Download Efficient emulation of tape-like delay modulation behavior A significant part of the appeal of tape-based delay effects is the manner in which the pitch of their output responds to changes in delay-time. Straightforward approaches to implementation of delays with tape-like modulation behavior result in algorithms with time complexity proportional to the tape speed, leading to noticeable increases of CPU load at smaller delay times. We propose a method which has constant time complexity, except during tape speedup transitions, where the complexity grows logarithmically, or, if proper antialiasing is desired, linearly with respect to the speedup factor.
Download A Combined Model for a Bucket Brigade Device and its Input and Output Filters Bucket brigade devices (BBDs) were invented in the late 1960s as a method of introducing a time-delay into an analog electrical circuit. They work by sampling the input signal at a certain clock rate and shifting it through a chain of capacitors to obtain the delay. BBD chips have been used to build a large variety of analog effects processing devices, ranging from chorus to flanging to echo effects. They have therefore attracted interest in virtual analog modeling and a number of approaches to modeling them digitally have appeared. In this paper, we propose a new model for the bucket-brigade device. This model is based on a variable samplerate, and utilizes the surrounding filtering circuitry found in real devices to avoid the need for the interpolation usually needed in such a variable sample-rate system.
Download Removing Lavalier Microphone Rustle With Recurrent Neural Networks The noise that lavalier microphones produce when rubbing against clothing (typically referred to as rustle) can be extremely difficult to automatically remove because it is highly non-stationary and overlaps with speech in both time and frequency. Recent breakthroughs in deep neural networks have led to novel techniques for separating speech from non-stationary background noise. In this paper, we apply neural network speech separation techniques to remove rustle noise, and quantitatively compare multiple deep network architectures and input spectral resolutions. We find the best performance using bidirectional recurrent networks and spectral resolution of around 20 Hz. Furthermore, we propose an ambience preservation post-processing step to minimize potential gating artifacts during pauses in speech.
Download A Micro-Controlled Digital Effect Unit for Guitars Here we present a micro-controlled digital effect unit for guitars. Different from other undergraduate projects, we used high-quality 16-bit Analog-to-Digital (A/D) and Digital-to-Analog (D/A) converters operating at 48kHz that respectively transfer data to and from a micro-controller through serial peripheral interfaces (SPIs). We discuss the design decisions for interconnecting all these components, the project of anti-aliasing (low-pass) filters, and additional features useful for players. Finally, we show some results obtained from this device, and discuss future improvements.
Download Creating Endless Sounds This paper proposes signal processing methods to extend a stationary part of an audio signal endlessly. A frequent occasion is that there is not enough audio material to build a synthesizer, but an example sound must be extended or modified for more variability. Filtering of a white noise signal with a filter designed based on high-order linear prediction or concatenation of the example signal can produce convincing arbitrarily long sounds, such as ambient noise or musical tones, and can be interpreted as a spectral freeze technique without looping. It is shown that the random input signal will pump energy to the narrow resonances of the filter so that lively and realistic variations in the sound are generated. For realtime implementation, this paper proposes to replace white noise with velvet noise, as this reduces the number of operations by 90% or more, with respect to standard convolution, without affecting the sound quality, or by FFT convolution, which can be simplified to the randomization of spectral phase and only taking the inverse FFT. Examples of producing endless airplane cabin noise and piano tones based on a short example recording are studied. The proposed methods lead to a new way to generate audio material for music, films, and gaming.
Download Autoencoding Neural Networks as Musical Audio Synthesizers A method for musical audio synthesis using autoencoding neural networks is proposed. The autoencoder is trained to compress and reconstruct magnitude short-time Fourier transform frames. The autoencoder produces a spectrogram by activating its smallest hidden layer, and a phase response is calculated using real-time phase gradient heap integration. Taking an inverse short-time Fourier transform produces the audio signal. Our algorithm is light-weight when compared to current state-of-the-art audio-producing machine learning algorithms. We outline our design process, produce metrics, and detail an open-source Python implementation of our model.
Download Audio style transfer with rhythmic constraints In this transformation we present a rhythmically constrained audio style transfer technique for automatic mixing and mashing of two audio inputs. In this transformation the rhythmic and timbral features of both input signals are combined together through the use of an audio style transfer process that transforms the files so that they adhere to a larger metrical structure of the chosen input. This is accomplished by finding beat boundaries of both inputs and performing the transformation on beat-length audio segments. In order for the system to perform a mashup between two signals, we reformulate the previously used audio style transfer loss terms into three loss functions and enable them to be independent of the input. We measure and compare rhythmic similarities of the transformed and input audio signals using their rhythmic envelopes to investigate the influence of the tested transformation objectives.
Download Parametric Synthesis of Glissando Note Transitions - A user Study in a Real-Time Application This paper investigates the applicability of different mathematical models for the parametric synthesis of fundamental frequency trajectories in glissando note transitions. Hyperbolic tangent, cubic splines and Bézier curves were implemented in a realtime synthesis system. Within a user study, test subjects were presented two-note sequences with glissando transitions, which had to be re-synthesized using the three different trajectory models, employing a pure sine wave synthesizer. Resulting modeling errors and user feedback on the models were evaluated, indicating a significant disadvantage of the hyperbolic tangent in the modeling accuracy. Its reduced complexity and low number of parameters were however not rated to increase the usability.
Download Towards Multi-Instrument Drum Transcription Automatic drum transcription, a subtask of the more general automatic music transcription, deals with extracting drum instrument note onsets from an audio source. Recently, progress in transcription performance has been made using non-negative matrix factorization as well as deep learning methods. However, these works primarily focus on transcribing three drum instruments only: snare drum, bass drum, and hi-hat. Yet, for many applications, the ability to transcribe more drum instruments which make up standard drum kits used in western popular music would be desirable. In this work, convolutional and convolutional recurrent neural networks are trained to transcribe a wider range of drum instruments. First, the shortcomings of publicly available datasets in this context are discussed. To overcome these limitations, a larger synthetic dataset is introduced. Then, methods to train models using the new dataset focusing on generalization to real world data are investigated. Finally, the trained models are evaluated on publicly available datasets and results are discussed. The contributions of this work comprise: (i.) a large-scale synthetic dataset for drum transcription, (ii.) first steps towards an automatic drum transcription system that supports a larger range of instruments by evaluating and discussing training setups and the impact of datasets in this context, and (iii.) a publicly available set of trained models for drum transcription. Additional materials are available at http://ifs.tuwien.ac.at/~vogl/dafx2018.
Download Stationary/transient Audio Separation Using Convolutional Autoencoders Extraction of stationary and transient components from audio has many potential applications to audio effects for audio content production. In this paper we explore stationary/transient separation using convolutional autoencoders. We propose two novel unsupervised algorithms for individual and and joint separation. We describe our implementation and show examples. Our results show promise for the use of convolutional autoencoders in the extraction of sparse components from audio spectrograms, particularly using monophonic sounds.