http://www.k-wave.org/forum/topic/multiple-reflections-seen-from-one-reflective-point-source Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 03:09:02 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/multiple-reflections-seen-from-one-reflective-point-source#post-5764 Wed, 23 Nov 2016 08:11:24 +0000 Bradley Treeby 5764@http://www.k-wave.org/forum/ <p>Hi ssg47,</p> <p>What do you do to your data to produce the linked image? Fixing the typo for <code>&#39;PlotSim&#39;</code>, the code you posted will run 200 simulations but not do anything with the data.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/multiple-reflections-seen-from-one-reflective-point-source#post-5748 Wed, 16 Nov 2016 21:22:54 +0000 ssg47 5748@http://www.k-wave.org/forum/ <p>Hi Dr. Treeby/Cox,</p> <p>I have been using the k-wave 2D simulation to simulate a certain ultrasound setup. It has worked for all me previous setups. But I set up a simulation for a different grid size and it doesn't seem to give what I would expect. My output looks like this: <a href="http://tinypic.com/r/29azm79/9" rel="nofollow">http://tinypic.com/r/29azm79/9</a><br /> which to me doesn't make any sense since I only have one point in the medium that is reflective. From previous experiments, it should look like the input signal but attenuated(~12000 peak to peak amplitude). If you could kindly provide some insight into what may be wrong, that would be great. Thank you!</p> <p>%clear all<br /> pml_x_size = 20;<br /> pml_y_size = 20;<br /> Nx = 512 - 2*pml_x_size; %256<br /> Ny = 450 - 2*pml_y_size; %96<br /> dx = 0.2e-3; % was 0.2e-3<br /> dy = 0.2e-3; %<br /> kgrid = makeGrid(Nx, dx, Ny, dy);<br /> gridx_pts =11;<br /> c0 = 1540; % [m/s]<br /> rho0 = 1000; % [kg/m^3]<br /> medium.sound_speed_ref = c0;<br /> medium.alpha_power = 1.5;<br /> medium.alpha_coeff = 0.75;</p> <p>t_end = (Nx*dx)*2.4/c0; % [s] % was 2.4<br /> kgrid.t_array = 0:15e-9:t_end; % was 15e-9<br /> source_strength = 1e6; % [Pa]<br /> tone_burst_freq = 1.875e6; % [Hz]<br /> tone_burst_cycles = 5;<br /> input_signal = source_strength*toneBurst(1/kgrid.dt, tone_burst_freq, tone_burst_cycles);</p> <p>source.p_mask = zeros(Nx,Ny);<br /> num_elements = 48; % [grid points]<br /> x_offset = 1 ; % [grid points]<br /> start_index = Ny/2 - round(num_elements/2) + 1;<br /> source.p_mask(x_offset, start_index:start_index + num_elements - 1) = 1;<br /> source.p = input_signal;</p> <p>sensor.mask = zeros(Nx,Ny);<br /> sensor.mask(x_offset, start_index:start_index + num_elements - 1) = 1;<br /> cwire = 3000;<br /> scattering_rho0 = cwire/1.5;<br /> %%<br /> Ny_tot = Ny + 400;<br /> p = 2;</p> <p>sound_speed_map = c0*ones(Nx, Ny_tot);<br /> density_map = rho0*ones(Nx, Ny_tot);<br /> xc = Nx - 7;<br /> yc = floor((Ny_tot/2)-2);<br /> scattering_region = makeDisc(Nx, Ny_tot, xc, yc,1);<br /> sound_speed_map(scattering_region == 1) = cwire;<br /> density_map(scattering_region == 1) = scattering_rho0;</p> <p>for psny = 0:199<br /> medium.sound_speed = sound_speed_map(:,(psny*2)+1:(psny*2)+1+Ny-1);<br /> medium.density = density_map(:,(psny*2)+1:(psny*2)+1+Ny-1);<br /> input_args = {'PMLInside', false, 'PMLSize', [pml_x_size, pml_y_size],'DataCast','gpuArray-single',PlotSim',false};<br /> sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor,input_args{:});<br /> figure;imagesc(medium.sound_speed);<br /> end </p>