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Distributed Acoustical Meshes on the Internet

Chris Chafe

Center for Computer Research in Music and Acoustics
(CCRMA)
Stanford University

The 2D Waveguide Mesh computes realistic-sounding simulations of struck plates. The early 90’s saw an initial flurry of development on the model but it hasn’t yet found the greater musical use that its interesting sonic qualities suggest are possible.

Computed in real time, arrays of mesh nodes pass signals back and forth from one memory location to another.

The present project goal is a real-time synthesis instrument made of a multitude of distributed nodes passing signals across the Internet.

Rectilinear mesh using 4-port scattering junctions and unit delays (Julius Smith)

Adding edge filters and reflections, Synthesis Toolkit (12x12 nodes)

Larger mesh (32x8 nodes) with enhancements described in C. Chafe, "Extensions to the 2D Waveguide Mesh for Modeling Thin Plate Vibrations" Proc. of the Int'l. Conf. on Sound and Vibration, Montreal, 2019

Swinging in space simulated by wavefield synthesis

Network version with nodes distributed over 21 workstations (3x3 nodes)

Sounds a bit like a tympani membrane!
  • 21 workstations: 9 are scattering junctions and 12 are mesh boundaries
  • Mesh size is 3x3 (but more computers, more nodes)
  • Input from an external signal (synthesized strike at adjustable locations but non-interpolated, quantized to an integer X/Y coordinate position)
  • Two outputs (lower left corner and center nodes)

What is internet acoustics?
It's made from: 
  • sound propagation
    uncompressed bi-directional streaming (JackTrip)
  •  junctions and reflections
    scattering nodes and filters (Faust) 

  • "Plucked" Internet Path (UC Berkeley / Stanford)
    C. Chafe, S. Wilson, D. Walling "Physical Model Synthesis with Application to Internet Acoustics" Proc. ICASSP, Orlando, 2002

Smaller network mesh, 8 workstations (1x2 nodes)

(left) S. Van Duyne and J. O. Smith, "Physical Modeling with the 2-D Digital Waveguide Mesh" Int'l. Conf. Math. and Computing, 1993
(right) T. Rossing, "The Physics of Kettledrums" Scientific American , Vol. 247, No. 5, 1982

Tympani

Network mesh (3x3 nodes) -- differences:
missing the kettle, passive non-linearity,
and stick / membrane interaction

The next version will be a set of hosts "out in the wild" running on commercial cloud servers that are geographically dispersed.

JackTrip rehearsals and concerts typically involve hub nodes running on AWS, Azure, Google or Linode servers. Geolocating the JackTrip hub servers near the performers cuts down on latency.

Ulimately, a distributed mesh of hubs and players could create a network drum and network drum circle.

Much to my delight no modifications to JackTrip were required. The experiment largely involved authoring a single script for coordinating remote JackTrip operation and...

Much to my delight no modifications to JackTrip were required. The experiment largely involved authoring a single script for coordinating remote JackTrip operation and a highly-reliable cluster of machines.

Much gratitude to CCRMA's sysadmin team Fernando Lopez-Lezcano and Nils Tonnätt for that.

Thanks for listening!

This deck available at
https://ccrma.stanford.edu/~cc/deck.js/asa2024/