http://www.k-wave.org/forum/topic/pressure-amplitude-of-the-reflected-wave-vs-theoretical-reflection-coefficient Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 00:13:32 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/pressure-amplitude-of-the-reflected-wave-vs-theoretical-reflection-coefficient#post-7014 Thu, 22 Aug 2019 17:30:13 +0000 Bradley Treeby 7014@http://www.k-wave.org/forum/ <p>Hi Umit,</p> <p>You could try any more theoretical book on acoustics, e.g., Foundations of Biomedical Ultrasound (Cobbold), or Acoustics: An Introduction to Its Physical Principles and Applications (Pierce).</p> <p>You might also encounter problems related to the stair-casing of the medium geometry (a circle can't be perfectly represented on a square grid).</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/pressure-amplitude-of-the-reflected-wave-vs-theoretical-reflection-coefficient#post-6979 Mon, 22 Jul 2019 16:28:22 +0000 umitarabul 6979@http://www.k-wave.org/forum/ <p>Dear Brad,</p> <p>You are right, the source is circular (2D) and the reflecting boundary is also circular. So the waves are always oblique to the reflection surface. The reason I chose such a geometry is to eliminate r dependency of the amplitude (r^2 for the intensity). I used the impedance based reflection coefficient calculation (R = (Z1-Z2)/(Z1+Z2)). Honestly, I did not know that this has 1D plane wave assumption behind it. Could you suggest some literature explaining this?</p> <p>Umit, </p> http://www.k-wave.org/forum/topic/pressure-amplitude-of-the-reflected-wave-vs-theoretical-reflection-coefficient#post-6963 Wed, 10 Jul 2019 13:49:59 +0000 Bradley Treeby 6963@http://www.k-wave.org/forum/ <p>Hi Umit,</p> <p>I haven't run your code, but it would seem your calculation of the reflection coefficient assumes a 1D plane wave normally incident on a planar boundary, which doesn't match your simulation (where the source is not planar).</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/pressure-amplitude-of-the-reflected-wave-vs-theoretical-reflection-coefficient#post-6953 Mon, 08 Jul 2019 12:04:40 +0000 umitarabul 6953@http://www.k-wave.org/forum/ <p>Hi,</p> <p>Does anyone have a comment on my question?</p> <p>Umit, </p> http://www.k-wave.org/forum/topic/pressure-amplitude-of-the-reflected-wave-vs-theoretical-reflection-coefficient#post-6940 Fri, 28 Jun 2019 14:14:55 +0000 umitarabul 6940@http://www.k-wave.org/forum/ <p>Hi All,</p> <p>I am trying to infer some quantitative pressure values that reaches a transducer from a multilayered solid. To start simple, I am now testing the reflected pressure from a layer interface. However, there is a discrepancy between the theoretical reflection coefficient (0.86) and the ratio of the incident and reflected waves (0.69). </p> <p>For that, designed a simple circular layout. I emit a tone-burst signal from a circular transducer and record pressures along the vertical radius. So if you check the sensor position 166 &gt;&gt; then the amplitude ratio of incident and reflected pressures gives 0.69. Is this difference expected? or Am I missing something?</p> <p>Here is the code I am using</p> <pre><code>% ========================================================================= % MATERIAL PROPERTIES % ========================================================================= mat1.speed_of_sound = 1482; %[m/s] mat1.density = 994; %[kg/m3] mat2.speed_of_sound = 8432; %[m/s] mat2.density = 2329; %[kg/m3] % ========================================================================= % SIMULATION GRID PARAMETERS % ========================================================================= dx = 16e-6; dy = dx; Nx = 1024; % [grid points] Ny = 1024; kgrid = kWaveGrid(Nx, dx, Ny, dy); PML_size_x = Nx/16; PML_size_y = Ny/16; PML_size = [PML_size_x PML_size_y]; PML_alpha = 3; % ========================================================================= % Layout Design % ========================================================================= r_source = 6e-3; % [m] r_layer1 = 10e-3; % [m] source_region_mask = ((kgrid.x).^2 + (kgrid.y).^2) &lt; r_source^2; layer1_mask = ((kgrid.x).^2 + (kgrid.y).^2) &lt; r_layer1^2; dilated_source_region = imdilate(source_region_mask, strel(&#39;disk&#39;, 1)); source_ring = ~source_region_mask &amp; dilated_source_region; % ========================================================================= % MEDIUM PROPERTY ASSIGNMENT % ========================================================================= medium.sound_speed = ones(Nx,Ny) * mat1.speed_of_sound; medium.density = ones(Nx,Ny) * mat1.density; medium.sound_speed(~layer1_mask) = mat2.speed_of_sound; medium.density(~layer1_mask) = mat2.density; medium.alpha_coeff = zeros(Nx,Ny); medium.alpha_power = 1.005; medium.sound_speed_ref = mat1.speed_of_sound; % ========================================================================= % SENSOR DEFINITION % ========================================================================= % define the sensor to record the pressure sensor.mask = ~ones(Nx, Ny); sensor.mask(1:Nx/2, Ny/2) = 1; sensor.record = {&#39;p&#39;}; % ========================================================================= % SOURCE DEFINITION % ========================================================================= % assign the source clearvars source; source.p_mask = source_ring; % define the driving signal source_freq = 5e6; % [Hz] source_strength = 1e6; % [Pa] source_cycles = 3; % number of tone burst cycles % create the time steps and the time array CFL = 0.1; % stability criteria for convergence t_end = 4e-6; % (tof) kgrid.makeTime(max(medium.sound_speed(:)), CFL, t_end); sigma = 0.6/source_freq; mu = 3 * sigma; source_sig = -source_strength*exp(-((kgrid.t_array-mu).^2./(2*(sigma^2)))).*sin(2*pi*source_freq*kgrid.t_array); source.p = source_sig; % ========================================================================= % ELASTIC SIMULATION % ========================================================================= % set the input arguments input_args = { &#39;PMLSize&#39;, PML_size, ... &#39;PMLAlpha&#39;, PML_alpha, ... &#39;PMLInside&#39;, true, ... &#39;DataCast&#39;, &#39;gpuArray-single&#39;, ... &#39;DataRecast&#39;, true, ... &#39;PlotSim&#39;, true, ... &#39;PlotFreq&#39;, 100, ... &#39;PlotScale&#39;, source_strength *[-1 1], ... &#39;RecordMovie&#39;, true, ... }; % run the simulation sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor, input_args{:}); refl_coeff = (mat1.speed_of_sound*mat1.density - mat2.speed_of_sound * mat2.density) / ... (mat1.speed_of_sound*mat1.density + mat2.speed_of_sound * mat2.density); sensor_pressure_env = abs(hilbert(plot(sensor_data.p(166,:))));</code></pre>