http://www.k-wave.org/forum/topic/recording-accoustic-intesity Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 04:36:32 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/recording-accoustic-intesity#post-5896 Fri, 21 Apr 2017 10:44:37 +0000 g.schober@skz.de 5896@http://www.k-wave.org/forum/ <p>Hi Brad,<br /> sorry for my delayed answer it took me some time to get a working Example but now I have one, it still doesn't give the real signal back.<br /> <pre><code>%% define important constants for the simulation SmoothWindow=&#39;Gaussian&#39;; Input={&#39;DataCast&#39;,&#39;gpuArray-single&#39;,&#39;PlotSim&#39;,false,&#39;Smooth&#39;,true,&#39;SmoothWindow&#39;,SmoothWindow,... &#39;DataRecast&#39;,true}; cc=[343 2330 2600 2600]; cs=[0 1060 1300 1300]; c_max=max([cc,cs]); rho=[1.2 1380 960 960]; Ampli=2; CFL=0.1; hoehe=0.0076/2; %[m] alphac=[0.0136,3,3,3]; alphas=[0,3,3,3]; frequence=218e3; %[Hz] t_end=8e-4; %[s] %% define grid variables and make the grid Nx=2^8; Ny=Nx; Nz=Nx; dx=0.09/Nx; dy=0.09/Ny; dz=0.09/Nz; kgrid=makeGrid(Nx,dx,Ny,dy,Nz,dz); kgrid.t_array=makeTime(kgrid,c_max,CFL,t_end); %% define additional matrizes and values radius=ceil(0.005*sqrt(2)/sqrt((dy)^2+(dz)^2))+1; pathname=[&#39;D:\Laurent\Luftultraschall_Simulation\PSTDRichtigeAnregung&#39;,num2str(Ampli)]; foldername=[num2str(round(Nx)),&#39;x&#39;,num2str(round(Ny)),&#39;x&#39;,num2str(round(Nz)),... &#39;_Absorbtion_&#39;,num2str(t_end*1e6),&#39;_us_&#39;,zeit]; %% define the model and the sensor and source position model=false(Nx,Ny,Nz); model((floor(-hoehe/dx)-1:ceil(hoehe/dx)+1)+round(Nx/2),:,:)=true; sensor.mask=false(Nx,Ny,Nz); sensor.mask(Nx/2+round((0.024+hoehe)/dx),:,:)=makeDisc(Ny,Nz,floor(Ny/2+1),floor(Nz/2+1),radius); source.u_mask=false(Nx,Ny,Nz); source.u_mask(Nx/2-round((0.03+hoehe)/dx),:,:)=makeDisc(Ny,Nz,floor(Ny/2+1),floor(Nz/2+1),radius); Absorbtion=false(Nx,Ny,Nz); Absorbtion(10:(Nx/2-round((0.03+hoehe)/dx)),:,:)= ~source.u_mask(10:(Nx/2-round((0.03+hoehe)/dx)),:,:); Absorbtion((Nx/2+round((0.024+hoehe)/dx)):(end-10),:,:)= ~sensor.mask((Nx/2+round((0.024+hoehe)/dx)):(end-10),:,:); %% create the input signal using toneBurst x=toneBurst(1/kgrid.dt,218e3,0.5,&#39;Envelope&#39;,&#39;Rectangular&#39;); x=[getWin(length(x),&#39;HalfBand&#39;).&#39;,zeros(size(x))]; input_signal=repmat(x,1,Ampli); input_signal = applyFilter(input_signal, 1/kgrid.dt, 2*frequence/3.5, &#39;LowPass&#39;); % disp(&#39;Adding noise to the input signal&#39;); % [input_signal,snr]=addNoise(input_signal,35); % disp([&#39;We have a Signal to Noise Ratio of: &#39;,num2str(snr)]); input_signal=[zeros(1,round(1e-6/kgrid.dt)),input_signal]; %% define the medium and the time array medium.sound_speed_compression=cc(1)*ones(Nx,Ny,Nz); medium.sound_speed_compression(model)=cc(2); medium.sound_speed_compression(sensor.mask)=cc(3); medium.sound_speed_compression(source.u_mask)=cc(4); medium.sound_speed_shear=cs(1)*ones(Nx,Ny,Nz); medium.sound_speed_shear(model)=cs(2); medium.sound_speed_shear(sensor.mask)=cs(3); medium.sound_speed_shear(source.u_mask)=cs(4); medium.density=rho(1)*ones(Nx,Ny,Nz); medium.density(model)=rho(2); medium.density(sensor.mask)=rho(3); medium.density(source.u_mask)=rho(4); medium.alpha_coeff_compression=alphac(1)*ones(Nx,Ny,Nz); medium.alpha_coeff_compression(model)=alphac(2); medium.alpha_coeff_compression(sensor.mask)=alphac(3); medium.alpha_coeff_compression(source.u_mask)=alphac(4); medium.alpha_coeff_compression(Absorbtion)=200; medium.alpha_coeff_shear=alphas(1)*ones(Nx,Ny,Nz); medium.alpha_coeff_shear(model)=alphas(2); medium.alpha_coeff_shear(sensor.mask)=alphas(3); medium.alpha_coeff_shear(source.u_mask)=alphas(4); medium.alpha_coeff_shear(Absorbtion)=200; %% define the remaining source values focus_point=[kgrid.x_vec(source.u_mask(:,ceil(Ny/2),ceil(Nz/2)))+0.025,0,0]; source.ux=focus(kgrid,input_signal,source.u_mask,focus_point,cc(1)); % source.u_mode=&#39;dirichlet&#39;; %% define the remaining sensor values sensor.record={&#39;p&#39;,&#39;p_final&#39;}; sensor.frequency_response=[ frequence , 13 ]; % [~,sensor.record_start_index]=findClosest(kgrid.t_array,50e-6); %% Simulation sensor_data=pstdElastic3D(kgrid,medium,source,sensor,Input{:});</code></pre> <p>I want to simulate a ultrasonic NDT tester with the model is in between the source and the sensor. Also it is a sort of plastic as the medium from the model. The rest is air.<br /> Best Regards </p> http://www.k-wave.org/forum/topic/recording-accoustic-intesity#post-5881 Tue, 04 Apr 2017 12:45:05 +0000 Bradley Treeby 5881@http://www.k-wave.org/forum/ <p>It's certainly possible to define a disk in an absorbing medium, but it's difficult to say more without knowing exactly your parameters. Do you have a working code example that you could post? </p> http://www.k-wave.org/forum/topic/recording-accoustic-intesity#post-5880 Tue, 04 Apr 2017 10:30:15 +0000 g.schober@skz.de 5880@http://www.k-wave.org/forum/ <p>Hi Brad,</p> <p>thank you for answering my questions and thank you for offering this toolbox for free. It is usefull for NDT.<br /> Now I have another question, would it be possible to define a disc or any other form on a transducer where the sound can leave and absorb it outside this area? Because when I tried that the simulation got unstable and reached infitiy pretty fast.<br /> Should I 'simply' make my grid thinner (I had 512 grid points on a length of 100mm and my frequenz is 218kHz) or my timesteps shorter to achieve stabability? </p> <p>Best regards </p> http://www.k-wave.org/forum/topic/recording-accoustic-intesity#post-5878 Tue, 04 Apr 2017 09:54:26 +0000 Bradley Treeby 5878@http://www.k-wave.org/forum/ <p>Hi g.schober,</p> <p>To answer your questions:</p> <p>(1) It's not currently possible to use the transducer class to record intensity.</p> <p>(2) Currently, only rectangular elements are supported, and the transducer must be aligned with the grid. In future versions of k-Wave, we intend to allow labelled source matrices to allow multi-element arrays of other types to be defined using the normal pressure and velocity sources.</p> <p>(3) <code>kspaceFirstOrder3D</code> is a fluid model, so doesn't account for transverse waves. If you want to model shear, you should use <code>pstdElastic3D</code>.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/recording-accoustic-intesity#post-5862 Tue, 21 Mar 2017 14:31:21 +0000 g.schober@skz.de 5862@http://www.k-wave.org/forum/ <p>Hi all,<br /> is it possible to record the time varying accoustic intensity with a transducer class and will there be a possibility to do other shapes than a rectangle with the kWaveTransducer? If not what could I change in the program to do so? And I have one more question, would it be possible to add the calculation of the longitudinal and transversal aspects of the wave in the 3D version of kspaceFirstOrder?<br /> Best Regards </p>