http://www.k-wave.org/forum/topic/understanding-absorption-parameters-mediumalpha_coeff-and-mediumalpha_power Support for the k-Wave MATLAB toolbox en-US Tue, 12 May 2026 23:39:19 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/understanding-absorption-parameters-mediumalpha_coeff-and-mediumalpha_power#post-7857 Tue, 29 Sep 2020 09:37:00 +0000 Bradley Treeby 7857@http://www.k-wave.org/forum/ <p>Hi emmal,</p> <p>By default, a perfectly matched layer (PML) is used at the walls, so the simulation will be the same as in an anechoic environment (you can read more about this in the examples and user manual).</p> <p>You can find some details about the absorption in air in <a href="http://www.k-wave.org/forum/topic/absorbtion-coefficents#post-522">this post</a>.</p> <p>Brad </p> http://www.k-wave.org/forum/topic/understanding-absorption-parameters-mediumalpha_coeff-and-mediumalpha_power#post-7856 Mon, 28 Sep 2020 22:34:27 +0000 emmal 7856@http://www.k-wave.org/forum/ <p>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. </p> <p>% =================<br /> % SIMULATION<br /> % =================</p> <p>% create the computational grid<br /> Nx = 250; % number of grid points in the x (row) direction<br /> Ny = Nx; % number of grid points in the y (column) direction<br /> dx = .01; % grid point spacing in the x direction [m]<br /> dy = dx; % grid point spacing in the y direction [m]<br /> kgrid = kWaveGrid(Nx, dx, Ny, dy);</p> <p>% define the properties of the propagation medium -- need to understand<br /> % these a bit better. 0.97 was selected based upon anechoic chambers at low<br /> % frequencies, but this determines properties of the PML<br /> medium.sound_speed = 330; % [m/s]<br /> medium.alpha_coeff = 1; % [dB/(MHz^y cm)]<br /> medium.alpha_power = 1.5; </p>