I'm new to K-wave and confused about what the absorption parameters, defined by the alpha parameters (medium.alpha_coeff and medium.alpha_power), should be set to in the code or how to go about understanding what one would want to set them to. A project I'm working on is simulating a low-frequency (120-230 Hz), linear phased array with four point sources representing transducers. Also, my group wants the sound waves to be absorbed completely at the walls and the medium to behave like atmospheric air in an anechoic environment. Attached is a section of our code showing these parameters. The alpha coefficient and alpha power values were set based on a sample simulation.
% =================
% SIMULATION
% =================
% create the computational grid
Nx = 250; % number of grid points in the x (row) direction
Ny = Nx; % number of grid points in the y (column) direction
dx = .01; % grid point spacing in the x direction [m]
dy = dx; % grid point spacing in the y direction [m]
kgrid = kWaveGrid(Nx, dx, Ny, dy);
% define the properties of the propagation medium -- need to understand
% these a bit better. 0.97 was selected based upon anechoic chambers at low
% frequencies, but this determines properties of the PML
medium.sound_speed = 330; % [m/s]
medium.alpha_coeff = 1; % [dB/(MHz^y cm)]
medium.alpha_power = 1.5;