http://www.k-wave.org/forum/topic/3d-modeling-of-the-room-reverberation-time Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 05:21:30 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/3d-modeling-of-the-room-reverberation-time#post-4603 Fri, 27 Jun 2014 10:10:40 +0000 Bradley Treeby 4603@http://www.k-wave.org/forum/ <p>Hi Yoojaeheon,</p> <p>If you are doing simulations at audible frequencies in air (particularly in the Hz to low-KHz range), the absorption coefficient is fairly small, so you could leave this undefined (you might also find <a href="http://www.k-wave.org/forum/topic/absorbtion-coefficents">this post</a> helpful). Similarly, the reflection from the concrete wall will be very high, so the absorption in the concrete is unlikely to have a large effect on your results.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/3d-modeling-of-the-room-reverberation-time#post-4601 Fri, 27 Jun 2014 05:16:47 +0000 Yoojaeheon 4601@http://www.k-wave.org/forum/ <p>K-wave tool to try to obtain the reverberation time. </p> <p> 6 of the concrete wall.</p> <p> Parameters in (medium.alpha_coeff) should I use?</p> <p> m code is</p> <p> clear all;</p> <p>% set the PML size<br /> PML_size = 10;</p> <p>% create the computational grid [ 3m by 3m domain ]<br /> Nx = 128- 2*PML_size; % number of grid points in the x (row) direction<br /> Ny = (128- 2*PML_size)/2; % number of grid points in the y (column) direction<br /> Nz = (128- 2*PML_size)/4;<br /> dx = 10/Nx; % grid point spacing in the x direction [m]<br /> dy = 5/Ny; % grid point spacing in the y direction [m]<br /> dz = 2.5/Nz;<br /> kgrid = makeGrid(Nx, dx, Ny, dy, Nz, dz);</p> <p>% define the properties of the propagation medium<br /> c_air = 330; % [m/s]<br /> rho_air = 1.225; % [kg/m^3]</p> <p>% define the properties of the wall<br /> c_wall = 3500; % [m/s]</p> <p>thickness = 5; % [grid points]</p> <p>% define the position of the wall<br /> wall = zeros(Nx, Ny, Nz);</p> <p>wall(1:thickness,:,:) = 1;<br /> wall(end-thickness+1:end,:,:) = 1;<br /> wall(:,1:thickness,:) = 1;<br /> wall(:,end-thickness+1:end,:) =1;<br /> wall(:,:,1:thickness) = 1;<br /> wall(:,:,end-thickness+1:end) = 1;</p> <p>% assign the medium properties<br /> medium.sound_speed = c_air*ones(Nx, Ny,Nz);<br /> medium.sound_speed(wall == 1) = c_wall;<br /> medium.density = rho_air*ones(Nx, Ny,Nz);<br /> medium.alpha_coeff = 4.6462e-06*ones(Nx,Ny,Nz);<br /> medium.alpha_coeff(wall==1)= 1.3049;<br /> medium.alpha_power = 0 ;<br /> medium.sound_speed_ref = c_air;</p> <p>% create the time array<br /> cfl = 0.2;<br /> t_end=2; % [s]<br /> [kgrid.t_array, dt] = makeTime(kgrid, medium.sound_speed, cfl, t_end);</p> <p>source_freq = 1000; % [Hz]<br /> source_mag = 20; % [Pa]<br /> source.p = source_mag*toneBurst(1/kgrid.dt, source_freq, 1);</p> <p>source.p_mask = zeros(Nx, Ny,Nz);<br /> source.p_mask(22, 27, 14) = 1;</p> <p>% define sensors everywhere<br /> %sensor.mask = ones(Nx,Ny,Nz );<br /> sensor.mask = zeros(Nx,Ny,Nz);<br /> %sensor.mask(45,54,54)=1;<br /> sensor.mask(52,27, 14)=1;<br /> sensor.mask(62,27, 14)=1;<br /> sensor.mask(72,27, 14)=1;<br /> %sensor.mask(89,54,54)=1;</p> <p>% define the acoustic parameters to record<br /> sensor.record = {'p'};</p> <p>input_args = {'PMLInside', false, 'PlotPML', false, 'PMLSize', PML_size, 'DataCast', 'single'};</p> <p>% run simulation<br /> sensor_data = kspaceFirstOrder3D(kgrid, medium, source, sensor, input_args{:}); </p> <p>-If you set the density of the concrete wall is not simulated.<br /> - medium.alpha_coeff = 4.6462e-06*ones(Nx,Ny,Nz); -&gt; air attenuation<br /> - medium.alpha_coeff(wall==1)= 1.3049; -&gt; concrete attenuation </p>