Room Reverberation Prediction and Synthesis

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Journal Title
Journal ISSN
Volume Title
School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2022-10-21
Date
2022
Major/Subject
Mcode
Degree programme
Language
en
Pages
76 + app. 86
Series
Aalto University publication series DOCTORAL THESES, 133/2022
Abstract
In this dissertation, the discussion is centered around the sound energy decay in enclosed spaces. The works starts with the methods to predict the reverberation parameters, followed by the room impulse response measurement procedures, and ends with an analysis of techniques to digitally reproduce the sound decay. The research on the reverberation in physical spaces was initiated when the first formula to calculate room's reverberation time emerged. Since then, finding an accurate and reliable method to predict reverberation has been an important area of acoustic research. This thesis presents a comprehensive comparison of the most commonly used reverberation time formulas, describes their applicability in various scenarios, and discusses their accuracy when compared to results of measurements. The common sources of uncertainty in reverberation time calculations, such as bias introduced by air absorption and error in sound absorption coefficient, are analyzed as well. The thesis shows that decreasing such uncertainties leads to a good prediction accuracy of Sabine and Eyring equations in diverse conditions regarding sound absorption distribution. The measurement of the sound energy decay plays a crucial part in understanding the propagation of sound in physical spaces. Nowadays, numerous techniques to capture room impulse responses are available, each having its advantages and drawbacks. In this dissertation, the majority of commonly used measurement techniques are listed, whereas the exponential swept-sine is described in more detail. This work elaborates on the external factors that may impair the measurements and introduce error to their results, such as stationary and non-stationary noise, as well as time variance. The dissertation introduces Rule of Two, a method of detecting non-stationary disturbances in sweep measurements. It also shows the importance of using median as a robust estimator in non-stationary noise detection. Artificial reverberation is a popular sound effect, used to synthesize sound energy decay for the purpose of audio production. This dissertation offers an insight into artificial reverberation algorithms based on recursive structures. The filter design proposed in this work offers precise control over the decay rate while being efficient enough for real-time implementation. The thesis discusses the role of the delay lines and feedback matrix in achieving high echo density in feedback delay networks. It also shows that four velvet-noise sequences are sufficient to obtain smooth output in interleaved velvet noise reverberator. The thesis shows that the accuracy of reproduction increases the perceptual similarity between measured and synthesised impulse responses. The insights collected in this dissertation offer insights into the intricacies of reverberation prediction, measurement and synthesis. The results allow for reliable estimation of parameters related to sound energy decay, and offer an improvement in the field of artificial reverberation.
Description
Supervising professor
Välimäki, Vesa, Prof., Aalto University, Department of Signal Processing and Acoustics, Finland
Thesis advisor
Schlecht, Sebastian J., Prof., Aalto University, Finland
Välimäki, Vesa, Prof., Aalto University, Finland
Keywords
audio effects, audio signal processing, impulse response measurements, reverberation, room acoustics
Other note
Parts
  • [Publication 1]: Karolina Prawda, Sebastian J. Schlecht, and Vesa Välimäki. Evaluation of Reverberation Time Models with Variable Acoustics. In Proceedings of the 17th Sound and Music Computing Conference (SMC 2020), Turin, Italy, June 2020. Full text in Acris/Aalto http://urn.fi/URN:NBN:fi:aalto-202011066382.
  • [Publication 2]: Karolina Prawda, Sebastian J. Schlecht, and Vesa Välimäki. Calibrating the Sabine and Eyring Formulas. The Journal of the Acoustical Society of America, Vol. 152, No. 2, pp. 1158–1169, August 2022.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202209215689
    DOI: 10.1121/10.0013575 View at publisher
  • [Publication 3]: Karolina Prawda, Sebastian J. Schlecht, and Vesa Välimäki. Robust Selection of Clean Swept-Sine Measurements in Non-Stationary Noise.The Journal of the Acoustical Society of America, Vol. 151, pp. 2117–2126, March 2022.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202204062736
    DOI: 10.1121/10.0009915 View at publisher
  • [Publication 4]: Vesa Välimäki and Karolina Prawda. Late-Reverberation Synthesis using Interleaved Velvet-Noise Sequences. IEEE/ACM Transactions onAudio Speech and Language Processing, Vol. 29, pp. 1149–1160, February 2021.
    DOI: 10.1109/TASLP.2021.3060165 View at publisher
  • [Publication 5]: Karolina Prawda, Sebastian J. Schlecht, and Vesa Välimäki. Improved Reverberation Time Control for Feedback Delay Networks. In Proceedings of the International Conference on Digital Audio Effects (DAFx 2019), Birmingham, UK, September 2019.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201909205308
  • [Publication 6]: Karolina Prawda, Silvin Willemsen, Stefania Serafin, and Vesa Välimäki. Flexible Real-Time Reverberation Synthesis with Accurate Parameter Control. In Proceedings of the International Conference on Digital Audio Effects (DAFx 2020), Vienna, Austria, September 2020.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202011066346
  • [Publication 7]: Karolina Prawda, Vesa Välimäki, and Stefania Serafin. Evaluation of Accurate Artificial Reverberation Algorithm. In Proceedings of the 17th Sound and Music Computing Conference (SMC 2020), Turin, Italy, June 2020.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202011066387
Citation