k-Wave User Forum » Topic: reflection coefficient

k-Wave User Forum » Topic: reflection coefficient http://www.k-wave.org/forum/topic/reflection-coefficient Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 02:29:25 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php RuiLiu on "reflection coefficient" http://www.k-wave.org/forum/topic/reflection-coefficient#post-7766 Mon, 24 Aug 2020 05:06:17 +0000 RuiLiu 7766@http://www.k-wave.org/forum/ Hi, we are doing the similar staff for kwave, I am also dealing the reflection issue. Please let me know if you want a discussion and you could leave wechat number below. Thanks. Bradley Treeby on "reflection coefficient" http://www.k-wave.org/forum/topic/reflection-coefficient#post-7746 Wed, 19 Aug 2020 15:01:23 +0000 Bradley Treeby 7746@http://www.k-wave.org/forum/ Hi ljx199, As far as I can tell, the two sensor positions are at different distances from the scattering object, so the amplitudes will be difference due to geometric spreading. Also, keep in mind that the scattering profile when you have a density perturbation is not uniform with angle. The expression for the scattered wave as a function of angle is in quite a few text books dating all the way back to Rayleigh Theory of Sound (vol 2. Scattering from a small sphere). Hope that helps, Brad. ljx199 on "reflection coefficient" http://www.k-wave.org/forum/topic/reflection-coefficient#post-7731 Mon, 10 Aug 2020 14:28:22 +0000 ljx199 7731@http://www.k-wave.org/forum/ Hi, I am using k-wave fro NDT simulation. In order to simulate a defect, I set up a circular region inside the object under test, whose sound velocity and density are different from the material under test. But I found in the simulation that the reflection coefficients of different angles are different. Is there any way to make the reflection coefficient the same in all directions as the sound wave travels to the defect? The echo signal received at two sensor positions does not satisfy (1/sqrt(r1))/(1/sqrt(r2)). So I think it's due to different reflectivity in different directions. Below is my program. Looking for ward your reply. Thank you very much. %Echo data obtained by FMC(full matrix capture) % simulation settings clearvars; clc; clear; % simulation settings DATA_CAST = 'single'; % ========================================================================= % DEFINE THE K-WAVE GRID % ========================================================================= % set the size of the perfectly matched layer (PML) PML_X_SIZE = 20; % [grid points] PML_Y_SIZE = 20; % [grid points] % set total number of grid points not including the PML Nx = 512 - 2*PML_X_SIZE; % [grid points] Ny = 512 - 2*PML_Y_SIZE; % [grid points] % calculate the spacing between the grid points dx = 0.1e-3; % [m] dy = dx; % [m] % create the k-space grid kgrid = kWaveGrid(Nx, dx, Ny, dy); % ========================================================================= % DEFINE THE MEDIUM PARAMETERS % ========================================================================= % define the properties of the propagation medium medium.sound_speed = 6200; % [m/s] medium.density = 2700; % [kg/m^3] % create the time array t_end = 10e-6; % [s] kgrid.makeTime(medium.sound_speed,[], t_end); % ========================================================================= % DEFINE THE INPUT SIGNAL Properities % ========================================================================= % define properties of the input signal source_strength = 1e6; % [Pa] tone_burst_freq = 5e6; % [Hz] tone_burst_cycles = 5; % ========================================================================= % DEFINE THE Excitation Source % ========================================================================= N_element = 32; %定义阵元数目 element_width = 4; %定义阵元宽度为4个网格点，即0.4mm kerf = 1; %定义阵元间隙为1个网格点，即0.1mm pitch = element_width + kerf; %定义阵元间距 % calculate the width of the transducer in grid points transducer_width = N_element * element_width ... + (N_element - 1) * kerf; x_start = round(Ny/2 - transducer_width/2); %x的起始网格点 y_start = 1; %y的起始网格点 source_mask = zeros(Nx, Ny, N_element); %定义与阵元数目相同的蒙版 for i = 1 : N_element x_temp = x_start + pitch * (i-1); x_element = (x_temp : x_temp + element_width -1); source_mask(y_start,x_element, i) = 1; end source.p_mask = source_mask(:, :, 16); %仅一个阵元被激励，获取全矩阵捕获回波信号 input_signal = toneBurst(1/kgrid.dt, tone_burst_freq, tone_burst_cycles); input_signal = (source_strength ./ (6200 * 2700)) .* input_signal; source.p = source_strength * input_signal; % ========================================================================= % DEFINE THE Sensor % ========================================================================= % define a single sensor point % sensor.mask = zeros(Nx, Ny); % sensor.mask(Nx/4, Ny/2) = 1; % sensor.mask(2*Nx/4, Ny/2) = 1; sensor.mask = source_mask(:, :, 1) + source_mask(:, :, 16); % define the acoustic parameters to record sensor.record = {'p'}; % ========================================================================= % DEFINE THE Defect % ========================================================================= %define a circle for the region of interesting sound_speed_map = ones(Nx, Ny); density_map = ones(Nx, Ny); radius = 1.5e-3; % [m] arc_angle = 2*pi; x = Nx * dx; y = Ny * dy; x_center = x/2; y_center = y/2; scattering_region1 = makeCircle(Nx, Ny, Nx/2, Ny/2, round(radius/dx), arc_angle); sound_speed_map(scattering_region1 == 1) = 1540; sound_speed_map(scattering_region1 == 0) = 6200; density_map(scattering_region1 == 1) = 1000; density_map(scattering_region1 == 0) = 2700; medium.sound_speed = sound_speed_map; medium.density = density_map; % ========================================================================= % Calculator the pressure % ========================================================================= % set the input settings input_args = { 'PMLInside', false, 'PlotPML', false, 'PMLSize', [PML_X_SIZE, PML_Y_SIZE], ... 'DataCast', DATA_CAST, 'PlotScale', [-1/20, 1/20] * source_strength}; % run the simulation sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor, input_args{:});