k-Wave User Forum » User Favorites: Crusher

k-Wave User Forum » User Favorites: Crusher crusher Support for the k-Wave MATLAB toolbox en-US Tue, 12 May 2026 23:08:55 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php frezaei on "I want to do a 2D elastic wave simulation on step geometry" http://www.k-wave.org/forum/topic/i-want-to-do-a-2d-elastic-wave-simulation-on-step-geometry#post-9225 Tue, 29 Jul 2025 02:59:04 +0000 frezaei 9225@http://www.k-wave.org/forum/ I have a follow-up question: when I change the frequency, I observe that the sensor signal is higher for a higher frequency than lower frequency. Why does this happen? The material has an attenuation coefficient that depends on frequency, so for higher frequencies, we should see a lower amplitude at the sensor. Why do I see the reverse behavior? I also tried to use the same number of cycles for each case, but again seeing the same behavior, I am interested to learn how the following papers simulated with reasonable results? paper1.K‑wave modelling of ultrasound wave propagation in aerogels and the effect of physical parameters on attenuation and loss paper2.Simultaneous use of pulse-echo and through-transmission methods in determining a combined reflection coefficient frezaei on "I want to do a 2D elastic wave simulation on step geometry" http://www.k-wave.org/forum/topic/i-want-to-do-a-2d-elastic-wave-simulation-on-step-geometry#post-9224 Mon, 28 Jul 2025 19:05:11 +0000 frezaei 9224@http://www.k-wave.org/forum/ Hello, I am new to k-wave simulation, and I am trying to simulate the attenuation through media. First of all, for medium.alpha_coeff, what should the unit be? dB/MHz.cm or Np/MHz.cm? Secondly, how do I make sure the attenuation through the medium is correct? I placed two sensors, one near the source and the other 1.1mm away, and now by looking at sensor signals, I see there is an attenuation, but if I consider the peak-to-peak value of the sensor signal, it does not follow this relationship: P=P0*exp(-alpha*f*x), why? Here is my code: % Define medium properties medium.sound_speed = zeros(Nx, Ny); medium.density = zeros(Nx, Ny); medium.sound_speed(:,:) = 5555; medium.density(:,:) = 2440; % Define attenuation coefficients (Np/(MHz^y cm)) medium.alpha_coeff = zeros(Nx, Ny); % in dB/(MHz^y cm) but K-Wave expects Np/(MHz^y m) medium.alpha_coeff(:,:) = 0.1; % low loss (converted to Np/(MHz^y m)) medium.alpha_power = 1.0; % frequency power medium.alpha_mode = 'no_dispersion'; % Simulation time cfl=0.3; t_end = 16e-6; % [s] sound_speed=5555; dt = cfl * dx / sound_speed; kgrid.makeTime(sound_speed, cfl,t_end) % Tone burst source settings sample_freq = 20e6; % [Hz] signal_freq = 1e6; % [Hz] num_cycles = 3; signal=toneBurst(sample_freq,signal_freq,num_cycles,'Plot',true); %Defining a single source point source.p_mask = zeros(Nx, Ny); source.p_mask(round(Nx/2), 1) = 1; % define a time varying sinusoidal source source_mag = 1e2; % Amplitude in Pascals source.p=source_mag *signal; % Initialize sensor mask with unique labels sensor.mask = zeros(Nx, Ny); % Sensor 1: label '1' in second row (just below source) sensor.mask(round(Nx/2), 2) = 1; % Sensor 2: label '2' in the row right after the glass layer sensor.mask(round(Nx/2), 24) = 1; sensor.record = {'p', 'p_final','I'}; % Run the simulation with memory-safe options input_args = {'PMLInside', false, 'PMLSize', 20, 'PMLAlpha',3, 'PlotPML', true, 'DataCast', 'single', 'PlotLayout', true,'RecordMovie', true}; % input_args = {'DisplayMask', display_mask,'PMLInside', false, 'PMLSize', 20, 'PMLAlpha',2, 'PlotPML', true, 'DataCast', 'single', 'PlotLayout', true}; sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor,input_args{:}); % Extract pressure signals p_signals = sensor_data.p; % [2 x Nt] Nt = length(kgrid.t_array); t_micro = (0:Nt-1) * kgrid.dt * 1e6; % Plot recorded signals figure; plot(t_micro, p_signals(1,:), 'b-', 'LineWidth', 1.5); xlabel('Time (µs)'); ylabel('Pressure (Pa)'); legend('Sensor 1 (near source)'); title('Pressure1 Time‑Series Recorded by Sensors'); figure; plot(t_micro, p_signals(2,:), 'r-', 'LineWidth', 1.5); xlabel('Time (µs)'); ylabel('Pressure (Pa)'); legend('Sensor 2 (after 1.1mm)'); title('Pressure2 Time‑Series Recorded by Sensors'); grid on; [row_sens, col_sens] = find(sensor.mask); figure; imagesc(x_mm, y_mm, medium.sound_speed'); axis image tight; colormap(jet); colorbar; xlabel('x (mm)'); ylabel('y (mm)'); title('Medium with Sensor and Source Locations'); hold on; % Plot source in red [row_src, col_src] = find(source.p_mask); plot(x_mm(row_src), y_mm(col_src), 'rs', 'MarkerSize', 8, 'LineWidth', 1.5); % Plot sensors in green plot(x_mm(row_sens), y_mm(col_sens), 'go', 'MarkerSize', 8, 'LineWidth', 1.5); legend('Source', 'Sensor'); Bradley Treeby on "I want to do a 2D elastic wave simulation on step geometry" http://www.k-wave.org/forum/topic/i-want-to-do-a-2d-elastic-wave-simulation-on-step-geometry#post-8959 Fri, 24 Nov 2023 17:39:56 +0000 Bradley Treeby 8959@http://www.k-wave.org/forum/ k-Wave probably isn't the best tool for modelling structures like this. I'd suggest looking at different FEM tools, or even the FEM tools within MATLAB. Crusher on "I want to do a 2D elastic wave simulation on step geometry" http://www.k-wave.org/forum/topic/i-want-to-do-a-2d-elastic-wave-simulation-on-step-geometry#post-8920 Tue, 03 Oct 2023 11:53:34 +0000 Crusher 8920@http://www.k-wave.org/forum/ I want to do a 2D elastic wave simulation on step geometry, like a small rectangle of different property placed on a big rectangle of different property. How to do that?