Sounding Liquids

Physically based models for liquids

spherical bubble model, no fluid simulator coupling

Grid based methods

bubbles can be smaller, slow, can be two-phase, spherical and non-spherical bubbles

Shallow water equations

simulate water surface, no breaking waves, real time, one phase, bubbles from distribution

Non spherical bubbles

decompose into spherical harmonics

Efficient numerical acoustic simulations

novel technique based on 3D adaptive regular decomposition, 100x faster than Finite Difference Time Domain and 10x less memory

Source of speedup

modal analysis of rectangular spaced and GPU

SOTA room acoustics

geometric techniques combined with explicit diffraction modeling, auralization software with hybrid image

Geometric approaches to acoustics

bean tracing, phonon tracing, frustum tracing

Advantages of geometric approaches

efficient and easy to understand

Difficulties of geometric approaches

diffraction and scattering, high-order reflections

Numerical acoustics

discretize and solve wave equation on a grid, slow and memory

Creative EAX

pre-baked reverb filters assigned manually to different parts of a map

Adaptive rectangular decomposition

numerical simulation of the wave equation, rectangular decomposition of a 3D scene, 6th order finite difference for interface transmission

Solution on a rectangular domain

modal analysis can be done analytically for a 3D rectangular space of size (lx, ly, lz) and perfectly reflective boundary

3D Discrete Cosine Transform

solution of Wave Equation within each rectangle computed using FFT on GPU

Limitations of techniques

staircasing errors near boundary, doesn’t handle frequency dependent absorption

Impulse response

how reflected sound is perceived, direct approach is costly

Computational challenges for acoustics

need sufficient spatial resolution to resolve smallest wavelength of interest, sufficiently small time

Finite Difference Time Domain

works on a uniform Cartesian grid, pressure sampled at cell centers

Interference

the resultant pressure at P due to two waves is their sum