Different views on room acoustics modeling
The general aim in physics-based room acoustics modeling is to determine how sound propagates in a room. It is a field that can be approached from many different angles. People with background in physics or mathematics tend to consider it as a problem of solving the wave equation or other related partial differential equations. On the contrary, those with background in computer science, especially in computer graphics, prefer to think in terms of geometrical acoustics where sound is modeled as rays, similarly as light is modeled in computer graphics. The third identifiable group is formed of people from the field of electrical engineering and signal processing. They like to see room acoustics modeling as a challenge of designing artificial reverberation filters that can be used to process audio signals.

In addition to the physics-based modeling techniques mentioned above, there is also an approach that is known as perceptually-based modeling in which audio is processed to encompass acoustic characteristics based on some more abstract description instead of starting from room geometry and materials as is customary in physics-based modeling. However, this area is out of the scope of this book which focuses only on the physics-based approaches.

My personal background is in computer science, which may be easily seen in the style of writing. Besides giving a general introduction to each topic, the main emphasis is in algorithmic descriptions of the techniques. Instead of going through all possible derivations and theoretical analysis of the techniques each section provides a collection of linked references to help the readers to go deeper in the techniques as well as seeing their origins. There exists plenty of other literature that covers those topics.

For whom the book is aimed and how to read it
I can imagine several different styles of utilizing the book, and I hope the readers will find even more innovative uses. The primary goal has been to provide material that can be used as a textbook in courses teaching room acoustics modeling. From that viewpoint, the book should benefit both the teachers and students. The visualizations hopefully help individual studying and at the same time those can be used in classroom settings to help explaining various concepts.

The depth of the course should be adjustable. On the light end, just going through all the visualizations with their instructions should give a quick overview of the techniques, and that is often sufficient. On the other end, it is possible to go through all the algorithmic descriptions, and based on those it should be possible to reach a level in which the students can replicate the techniques and start experimenting with them by themselves.

One possible use scenario is to utilize the visualizations in explaining the basic concepts of room acoustics without paying attention to the actual modeling techniques. I believe that there are plenty of courses that introduce the basic concepts of room acoustics, and it would be great if this book could help in that task as well.

Getting feedback
It is my hope that you will find the book helpful and that it aids you in learning basic concepts of room acoustics and how to model it. I am eager to improve the contents on a continuous basis, and thus I am happy to hear any feedback or suggestions for improvements in the e-mail address:

Background of this book
I like programming, and I have always liked it. In my current job as a professor there is not too much time for coding such that it would start to feel dull or routine. To keep up at least some skill level, I every now and then try to devote some time for personal projects. In 2009, I decided to learn a new language (Ruby), and implemented a small application called 'SoundRad' that can be used to help teaching basics of room acoustics. I used it in some presentations at conferences and it was used also in actual teaching by my colleague Tapio Lokki. People seemed to like it, and I started to consider whether it would be possible to make a version that could be used by anyone and on any platform. That led me to consider making an online version of the tool expanded with textual explanations such that the result would be an interactive text-book. The coming sabbatical would be an excellent opportunity for such an effort.

Before the sabbatical started I spent some time investigating various opportunities on how to implement an interactive book. It was quite easy to see that the most accessible form of publication would be one that could be read by a web browser. This decision limited the available tools quite a lot, and in the end Javascript seemed to be the best option. The final confirmation for that decision came after the colleagues in Lund, Sweden, released their great Immersive linear algebra interactive textbook, and one of the authors, Tomas Akenine-Möller, told that they had taken exactly that path. So, I started the sabbatical by studying yet another new language, Javascript, and now, close to the end of the sabbatical, some of the results are available in this book.

The starting point for structure and texts in this book was the Overview of geometrical room acoustic modeling techniques article I wrote together with Peter Svensson. This work was started in 2013 and it finally got published in 2015. The paper emphasizes history and development of each technique and their mutual relations whereas this book has a more educational focus.

I hope you enjoy it!

A large part of the book was prepared during my sabbatical in 2015-2016. I would like to thank CCRMA (Center for Computer Research on Music and Acoustics) at Stanford University for hosting me during the sabbatical. Aalto University, Jenny and Antti Wihuri Foundation, and Nokia Foundation are acknowledged for their financial support that enabled the sabbatical.

In addition, I want to express my gratitude to the following persons for their feedback and/or support in preparing the book (the list is continuously updated, so, everyone is welcome to give feedback and it is appreciated!):

Lauri Savioja

Copyright notices
The following parts utilized in the book are from external sources:

All the other contents of the book are copyright by Lauri Savioja. The Javascript source files are available and can be used under the MIT License.

In addition, the site utilizes Google Analytics to gather statistics on usage.

Preface to version 0.1
At the time of first publication of the book (May, 2016), only the geometrical acoustics section is finished. All the other parts are still under preparation. My sabbatical is ending soon, and this means that I shall have much more limited time available for the book. The other sections are coming, but at this time, I can't promise any publication schedule for those.