The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Localization and Tracing of Early Acoustic Reflections in Enclosures

Sakari Tervo

Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the School of Science for public examination and debate in Auditorium T2 at the Aalto University School of Science (Espoo, Finland) on the 13th of January 2012 at 12 noon.

Overview in PDF format (ISBN 978-952-60-4438-5)   [14719 KB]
Dissertation is also available in print (ISBN 978-952-60-4437-8)


Objective room acoustic studies are conducted by measuring room impulse responses. The standard techniques include the use of an omni-directional source and, in most cases, one omni-directional microphone. This approach is well defined when measuring the standard room acoustic parameters.

Recently, early reflections, the first arriving sound waves in the room impulse response after the direct sound, have gained attention in research. The spatial location of the early reflections, i.e., the location of the image-source, can be used in room acoustic studies, auralization, room geometry inference, and in-situ measurement of acoustic properties of surfaces from room impulse responses. The location, however, cannot be obtained from the standard room impulse response measurement. Therefore, special microphone array techniques have been used for spatial analysis of room impulse responses.

This thesis studies the localization of early reflections. Firstly, a measurement technique of room impulse responses with directional loudspeakers is proposed. This allows better spatial and temporal separability between the reflections than the standard omni-directional loudspeaker.

Secondly, the use of microphone array techniques on the localization of early reflections is studied. Several techniques used in other localization tasks are transformed and applied for the localization of early reflections. In detail, the combination of time of arrival and time difference of arrival is researched. Moreover, interpolation of the time difference of arrival estimation function is proposed. The use of sound intensity vector based localization is also considered.

Finally, novel ad-hoc localization techniques for early reflections are proposed. Results for theoretical, simulation, and real data experiments are presented.

This thesis consists of an overview and of the following 6 publications:

  1. Sakari Tervo, Jukka Pätynen, and Tapio Lokki. Acoustic Reflection Path Tracing Using A Highly Directional Loudspeaker. In Proceedings of the 2009 IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA 2009) p. 245-248, New Paltz, NY, USA, October 18-21 2009.
  2. Sakari Tervo, Lauri Savioja, and Tapio Lokki. Maximum Likelihood Estimation of Loudspeaker Locations from Room Impulse Responses. Journal of the Audio Engineering Society, (In press) 14 pages, 2012.
  3. Sakari Tervo. Direction Estimation Based on Sound Intensity Vectors. In Proceedings of the 2009 European Signal Processing Conference (EUSIPCO 2009), p. 700-704, Glasgow, Scotland, August 24-28 2009.
  4. Sakari Tervo and Teemu Korhonen. Estimation of Reflective Surfaces from Continuous Signals. In Proceedings of the 35th International Conference on Acoustics, Speech, and Signal Processing, (ICASSP 2010), p. 153-156, Dallas, TX, USA, March 14-19 2010.
  5. Sakari Tervo and Tapio Lokki. Interpolation Methods for the SRP-PHAT Algorithm. In Proceedings of the 11th International Workshop for Acoustic Echo and Noise Control (IWAENC 2008), Article ID 9037, Seattle, WA, USA, September 14-17 2008.
  6. Sakari Tervo, Teemu Korhonen, and Tapio Lokki. Estimation of Reflections from Impulse Responses. Journal of Building Acoustics, Volume 18, Number 1-2, p. 159-174, March 2011.

Errata of publication 4

Keywords: early reflections, localization, room acoustics

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© 2012 Aalto University

Last update 2012-10-31