Neural Modelling of Audio Effects

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2023-12-15
Degree programme
54 + app. 86
Aalto University publication series DOCTORAL THESES, 217/2023
Neural networks and other machine learning based approaches to audio effects processing have become increasingly popular in recent years. This thesis focuses on the design and training of neural network architectures for the emulation of specific analog audio devices from data. The digital emulation of analog audio devices is commonly known as virtual analog, and popular effects processing devices for virtual analog modelling include guitar amplifiers, distortion pedals, time-varying effects, and compressors. Whilst analytical methods based on circuit analysis are capable of producing realistic, efficient and accurate models of devices, these approaches are limited by the fact that creating a model of a specific device is time-consuming and requires expert knowledge. In contrast, neural network based methods allow for greater automation in the modelling process, and can be applied relatively easily to a range of devices as long as sufficient data is available. This thesis proposes a number of neural network based methods for audio effects modelling, and shows that they achieve excellent perceptual emulation quality. The proposed models include convolutional, recurrent and differentiable digital signal processing based architectures. There is a focus on models with low computational cost and low latency, such that they are suitable for real-time processing as part of a music production workflow. Methods for modelling Low-Frequency Oscillator (LFO) modulated time-varying effects, compressors, guitar amplifiers and distortions pedals are proposed. In addition to the neural network architectures themselves, this thesis also provides practical details and methods for training the models. This includes the proposal and validation of a novel perceptually motivated pre-emphasis filter, used to model non-linear audio effects processing. Additionally a pruning method is applied and shown to achieve significant reduction in model size and inference cost for guitar amplifier and distortion effects modelling. Finally, this thesis presents a novel method for the task of modelling non-linear audio effects processing when paired training data is unavailable. This allows for complex non-linear effects processing to be emulated from recordings, whilst requiring no knowledge of the specific devices used to create the recording.
Supervising professor
Välimäki, Vesa, Prof., Aalto University, Department of Information and Communications Engineering, Finland
Thesis advisor
Välimäki, Vesa, Prof., Aalto University, Department of Information and Communications Engineering, Finland
audio effects processing, deep learning, neural networks, nonlinear systems, machine learning
Other note
  • [Publication 1]: A. Wright, E.-P. Damskägg and V. Välimäki. Real-time black-box modelling with recurrent neural networks. In Proc. 22nd Int. Conf. Digital Audio Effects (DAFx), Birmingham, UK, Sept. 2019.
  • [Publication 2]: A. Wright, E.-P Damskägg, L. Juvela and V. Välimäki. Real-time guitar amplifier emulation with deep learning. Applied Sciences, Vol. 10, No. 3, Jan. 2020.
    DOI: 10.3390/app10030766 View at publisher
  • [Publication 3]: A. Wright and V. Välimäki. Neural modeling of phaser and flanging effects. J. Audio Eng. Soc., Vol. 69, No. 7/8, pp. 517-529, July 2021.
    DOI: 10.17743/jaes.2021.0029 View at publisher
  • [Publication 4]: A. Wright and V. Välimäki. Grey-box modelling of dynamic range compression. In Proc. Int. Conf. on Digital Audio Effects (DAFx 20in22), Vienna, Austria, pp. 304-311, Sept. 2022.
  • [Publication 5]: A. Wright and V. Välimäki. Perceptual loss function for neural modeling of audio systems. In Proc. IEEE Int. Conf. Acoustics, Speech and Signal Processing (ICASSP 2020), Barcelona, Spain, pp. 251-255, May 2020.
    DOI: 10.1109/ICASSP40776.2020.9052944 View at publisher
  • [Publication 6]: D. Südholt, A. Wright, C. Erkut and V. Välimäki. Pruning deep neural network models of guitar distortion effects. IEEE/ACM Trans. on Audio, Speech, and Language Processing, Vol.31, pp. 256-264, Nov. 2022.
    DOI: 10.1109/TASLP.2022.3223257 View at publisher
  • [Publication 7]: A. Wright, V. Välimäki and L. Juvela. Adversarial guitar amplifier modelling with unpaired data. Proc. IEEE Int. Conf. Acoustics, Speech and Signal Processing (ICASSP 2023), Rhodes, Greece, June 2023.
    DOI: 10.1109/ICASSP49357.2023.10094600 View at publisher