Square rooms 2: Comparison of an anechoic chamber and a room with flat walls, with dissipation

Like the video Square rooms: Comparison of an anecho... this simulation compares wave propagation in an anechoic room (left) and in a rectangular room (right). Unlike in the previous video, the walls are able to absorb part of the energy. The speed of propagation in the walls surrounding the rooms is equal to 75% of the speed inside (the index of refraction is 1.333...), and there is also viscous dissipation in the walls. One can see that the energy of the waves is much more evenly spread across the anechoic room than across the rectangular one, and also decreases faster as time goes on.
The simulation has two parts, showing the same wave with two different representations:
Average energy (log scale): 0:00
Energy (log scale): 1:08
In the first part, both the z-coordinate and the color hue show the energy averaged from the beginning of the simulation up to the current time, on a logarithmic scale (which would be measured in decibels in the case of sound waves). In the second part, they show the instantaneous energy, also on a logarithmic scale.

Render time: 1 hour 2 minutes
Color scheme: Part 1 - Inferno by Nathaniel J. Smith and Stefan van der Walt
Part 2 -  Viridis by Nathaniel J. Smith, Stefan van der Walt and Eric Firing
https://github.com/BIDS/colormap

Music: "Thank You R.G.E." by Joe Bagale

See also https://images.math.cnrs.fr/Des-ondes... for more explanations (in French) on  a few previous simulations of wave equations.

The simulation solves the wave equation by discretization. The algorithm is adapted from the paper https://hplgit.github.io/fdm-book/doc...
C code: https://github.com/nilsberglund-orlea...
https://www.idpoisson.fr/berglund/sof...
Many thanks to my colleague Marco Mancini for helping me to accelerate my code!

• #science_technology
• #probability_theory
• #stochastic_processes