Didgmo: DIDGeridoo Sound MOdeling

Original project by Hanspeter Portner (SourceForge repository)
JavaScript port by cvogt729
License: zlib/libpng

Didgmo is an open-source tool for didgeridoo sound modeling, based on established techniques for simulating horn-like instruments. It helps you understand and design your instrument before you build it by simulating the sound characteristics of a didgeridoo based on its internal geometry.

Why Didgmo?

• Predict sound qualities in advance: Simulate acoustics before construction to reduce trial and error, save time and materials, and craft didgeridoos with specific acoustic goals.
• For builders and enthusiasts: Didgmo is practical for both experimentation and precision.
• Runs anywhere: Didgmo is serverless, can run offline, and works on almost any device.

How Does It Work?

Didgmo uses acoustic transmission line modeling. The inner geometry is divided into conical and cylindrical segments, and the transmission line matrix chain is solved in the complex domain for frequencies from 0 to 800 Hz. This produces the impedance, ground, and overblow spectrum for your design, helping you tune and optimize your didgeridoo's geometry.

How to Use

1. Download Didgmo:

   • Get the latest release as a single zip file from didgmo.zip.

2. Unzip:

   • Extract the contents of the zip file to any folder on your computer.

3. Run Didgmo:

   • Open didgmo.html in your favorite web browser. No installation or internet connection is required after download.

4. Input your geometry:

   • Enter your didgeridoo's geometry in the input area, one segment per line, starting with the mouth and ending with the bell.
   • Each line should have two numbers (position and diameter, in meters), separated by a space.
   • Example:

     0.000000 0.040000
     0.114286 0.055389
     0.228571 0.051429
     0.342857 0.057143
     0.457143 0.044921
     0.605099 0.067917
     0.677071 0.079468
     0.800402 0.080000
     0.914688 0.108450
     1.019101 0.095564
     1.168584 0.097143
     1.282870 0.106442
     1.364369 0.108571
     1.478654 0.114286
     1.592940 0.120000
     

5. Submit:

   • Press Submit to generate charts showing the sound spectra of your instrument.

Libraries

• Math.js for computations with complex numbers (mathjs.org)
• Chart.js for data visualization (chartjs.org)
• chartjs-plugin-annotation for chart annotations (chartjs.org/chartjs-plugin-annotation)
• All third-party JavaScript libraries can be downloaded from cdnjs.com/libraries

Method & Inspiration

Didgmo is inspired by the chapter "Computer Aided Didgeridoo Sound Design" in the book Das Didgeridoo-Phänomen. For more information, visit didgeridoo-physik.de.

Key References

• Lindner, David. Das Didgeridoo-Phänomen. Von der Urzeit zur Moderne. 2nd ed., Traumzeit-Verlag, 2003.
• Mapes-Riordan, D. "Horn Modeling with Conical and Cylindrical Transmission-Line Elements." J. Audio Eng. Soc 41, no. 6 (1993): 471-482.
• Caussé, René. "Input impedance of brass musical instruments - Comparison between experiment and numerical models." J. Acoust. Soc. Am. 75, no. 1 (1984): 241-254.

Example