k-Wave User Forum » User Favorites: zia.roghani

k-Wave User Forum » User Favorites: zia.roghani ziaroghani Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 00:28:38 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php Bradley Treeby on "Modelling a 2D simple room(bounded by 4 walls ) with an audible sound source ." http://www.k-wave.org/forum/topic/modelling-a-2d-simple-roombounded-by-4-walls-with-an-audible-sound-source#post-5158 Sun, 19 Jul 2015 13:02:35 +0000 Bradley Treeby 5158@http://www.k-wave.org/forum/ Hi Zia, There is no way to directly define an impedance boundary condition in k-Wave. However, you could define the material properties of your walls based on the equation for the plane wave pressure reflection coefficient at normal incidence, i.e., R = (Z2 - Z1) / (Z2 + Z1), where Z1 and Z2 are the characteristic acoustic impedance of the two media. Assuming the inner medium is air, then Z1 = 343 * 1.225 = 420. For R = 0.5, then Z2 = Z1 * (1 + R) / (1 - R) = 1260. You can then split this into the desired sound speed and density in the second medium. We have not derived an expression between reflection coefficient and the PML parameters - the data in Fig. 2.3 was derived by running numerical experiments. Generally speaking, the default values of PML thickness (20 grid points) and PML absorption (2 Nepers per grid point) work well. If you want to test a different range it's reasonably straightforward to do - send a wave into the PML and measure the amplitude of the transmitted and reflected waves. Brad. zia.roghani on "Modelling a 2D simple room(bounded by 4 walls ) with an audible sound source ." http://www.k-wave.org/forum/topic/modelling-a-2d-simple-roombounded-by-4-walls-with-an-audible-sound-source#post-5143 Tue, 14 Jul 2015 17:10:07 +0000 zia.roghani 5143@http://www.k-wave.org/forum/ Hello Bradely Treeby, I want to have the reflection co-effiecnt= 0.5, or 0.6 for the walls arround. The medium.sound_speed =330 ; What should be the values of medium.alpha_coeff, medium.alpha_power and PML_size. What is the numerical relationship between reflection,PLM(Thickness in grid point) and PML absorption as mention at pag 17,18 and figure 2.3. zia.roghani on "simulation using acoustic signal to determine material type in underwater" http://www.k-wave.org/forum/topic/simulation-using-acoustic-signal-to-determine-material-type-in-underwater#post-4840 Mon, 17 Nov 2014 18:31:44 +0000 zia.roghani 4840@http://www.k-wave.org/forum/ hay panda16 ope you will be fine. i am intrested in your work. could we please share it. Bradley Treeby on "Linear Sensors Array and sound source simulation" http://www.k-wave.org/forum/topic/linear-sensors-array-and-sound-source-simulation#post-4835 Tue, 11 Nov 2014 17:28:20 +0000 Bradley Treeby 4835@http://www.k-wave.org/forum/ Hi Zia, If you are using an object of the <code>kWaveTransducer</code> class, it is only possible to have a single linear array. However, if you define <code>sensor.mask</code> to be a binary matrix or cuboid corners, you can define an arbitrary number of sensor points in any configuration. You can assign any signal as your source (e.g., a recorded voice). You will need to assign this to <code>source.p</code>. Keep in mind that you need to make sure the sampling rate used in the recording matches the sampling rate (i.e., 1/kgrid.dt) used in the simulation. You might find it helpful to work through the examples included in the toolbox from the beginning, as well as reading the k-Wave manual. They contain lots of helpful information relevant to your questions. Good luck, Brad. zia.roghani on "Linear Sensors Array and sound source simulation" http://www.k-wave.org/forum/topic/linear-sensors-array-and-sound-source-simulation#post-4832 Fri, 07 Nov 2014 14:23:02 +0000 zia.roghani 4832@http://www.k-wave.org/forum/ Hi Hypermoi, you help is helpfull.As you are an expert. i have few question to ask. 1: can we define more then one Linear sensors array.if yes pleas tell me how..? 2: is it possible to use some recorded voice as source. Your help will be highly appreciated. Regards.. Anthony on "Linear Sensors Array and sound source simulation" http://www.k-wave.org/forum/topic/linear-sensors-array-and-sound-source-simulation#post-4719 Wed, 17 Sep 2014 12:56:15 +0000 Anthony 4719@http://www.k-wave.org/forum/ Hi Zia, You should have a look at the examples. Specifically, to set the position of your sensors, you can define a binary mask as explained in this example: <a href="http://www.k-wave.org/documentation/example_ivp_recording_particle_velocity.php">example</a>. Feel free to ask if you need more details after reading the examples. Anthony zia.roghani on "Linear Sensors Array and sound source simulation" http://www.k-wave.org/forum/topic/linear-sensors-array-and-sound-source-simulation#post-4718 Tue, 16 Sep 2014 18:08:12 +0000 zia.roghani 4718@http://www.k-wave.org/forum/ Dear all.. I have 5 sensors placed in a linear configuration at known location. There is a sound source at a specific bearing/angle(bearing/angle of the source is variable)and known distance from the sensors array. I want to record the signal received at each sensors. Please help me simulating the scenario in K-wave. i will be really very thankful. Bradley Treeby on "Modelling a 2D simple room(bounded by 4 walls ) with an audible sound source ." http://www.k-wave.org/forum/topic/modelling-a-2d-simple-roombounded-by-4-walls-with-an-audible-sound-source#post-4365 Fri, 14 Mar 2014 12:49:04 +0000 Bradley Treeby 4365@http://www.k-wave.org/forum/ Hi Gurashish, There are a few possibilities. You could try imposing a boundary condition explicitly as discussed <a href="http://www.k-wave.org/forum/topic/room-enclouse-acoustic-simulation">here</a>. However, this would still require the boundary to be several grid points thick. Alternatively, if you're familiar with spectral methods, you could replace the FFTs with discrete cosine and sine transforms to directly enforce Neumann and Dirichlet boundary conditions at the edge of the grid. Brad. Gurashish singh on "Modelling a 2D simple room(bounded by 4 walls ) with an audible sound source ." http://www.k-wave.org/forum/topic/modelling-a-2d-simple-roombounded-by-4-walls-with-an-audible-sound-source#post-4359 Mon, 03 Mar 2014 22:02:13 +0000 Gurashish singh 4359@http://www.k-wave.org/forum/ thank you ! that certainly clears my concepts . Incase if i just want to keep the boundaries completely reflective , without having to assign a number of grid points to the wall ! could i do that ? what change do i make to the code . ? Bradley Treeby on "Modelling a 2D simple room(bounded by 4 walls ) with an audible sound source ." http://www.k-wave.org/forum/topic/modelling-a-2d-simple-roombounded-by-4-walls-with-an-audible-sound-source#post-4351 Fri, 28 Feb 2014 10:45:48 +0000 Bradley Treeby 4351@http://www.k-wave.org/forum/ Hi Gurashish, Consider a plane wave that is normally incident on a boundary. Let the characteristic acoustic impedance of the first medium be Z1 = rho1*c1 and the impedance of the second medium be Z2 = rho2*c2. When Z2 >> Z1 (as in the case of air and concrete), the pressure reflection coefficient will approach 1, and the pressure transmission coefficient will approach 2. As k-Wave plots pressure, this is the reason the colour scale looks darker in the concrete. However, in this case, the transmission of energy into the second medium will approach zero (where T_e = 1 - R_p^2). This is clear if you consider the particle velocity of the plane wave in the second medium, which is given by u = p / Z2. As the particle velocity approaches 0, the transmitted intensity (given by I = p*u) will also approach 0. You can find more details in any introductory book on acoustics, for example, Kinsler & Frey. Hope that helps, Brad. Gurashish singh on "Modelling a 2D simple room(bounded by 4 walls ) with an audible sound source ." http://www.k-wave.org/forum/topic/modelling-a-2d-simple-roombounded-by-4-walls-with-an-audible-sound-source#post-4347 Thu, 27 Feb 2014 02:15:20 +0000 Gurashish singh 4347@http://www.k-wave.org/forum/ Hi brad, Thanks so much for the help firstly . Using your above described code i m afraid of the colour of the pressure field that propagates through the walls while the simulation shows the pressure field being generated(it becomes RED as sound waves start to reflect from them, while the tone burst source has YELLOW waves propagating that makes me feel that most of the waves are entering entering the walls . I m afraid if much of waves are passing through the walls into the PML described outside the grid and hence leading to attenuation of energy. Incase you feel the same . Is there a solution to this .? clear all; % set the PML size PML_size = 20; % create the computational grid [ 3m by 3m domain ] Nx = 128 - 2*PML_size; % number of grid points in the x (row) direction Ny = 128 - 2*PML_size; % number of grid points in the y (column) direction dx = 3/Nx; % grid point spacing in the x direction [m] dy = 3/Ny; % grid point spacing in the y direction [m] kgrid = makeGrid(Nx, dx, Ny, dy); % define the properties of the propagation medium c_air = 330; % [m/s] rho_air = 1.225; % [kg/m^3] % define the properties of the wall c_wall = 3200; % [m/s] concrete walls rho_wall = 2300; % [kg/m^3] thickness = 5; % [grid points] % define the position of the wall wall = zeros(Nx, Ny); wall(1:thickness, :) = 1; wall(end - thickness + 1:end, :) = 1; wall(:, 1:thickness) = 1; wall(:, end - thickness + 1:end) = 1; % assign the medium properties medium.sound_speed = c_air*ones(Nx, Ny); medium.sound_speed(wall == 1) = c_wall; medium.density = rho_air*ones(Nx, Ny); medium.density(wall == 1) = rho_wall; % set the reference sound speed used in the k-space operator medium.sound_speed_ref = c_air; % create the time array cfl = 0.1; t_end = 20e-3; % [s] [kgrid.t_array, dt] = makeTime(kgrid, medium.sound_speed, cfl, t_end); % define a time varying sinusoidal source source_freq = 1.5e3; % [Hz] source_mag = 50; % [Pa] source.p = source_mag*toneBurst(1/kgrid.dt, source_freq, 3); % define a single source point source.p_mask = zeros(Nx, Ny); source.p_mask(60, 40) = 1; % define sensors everywhere sensor.mask = ones(Nx, Ny); % define the acoustic parameters to record sensor.record = {'p'}; % run simulation sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor, ... 'PMLInside', false, 'PlotPML', false, 'PMLSize', PML_size, ... 'DisplayMask', 'off', 'PlotScale', [-0.25, 0.25]*source_mag,... 'DataCast', 'single'); % plot the recorded data figure; subplot(2, 1, 1) plot(kgrid.t_array(1:length(source.p)), source.p); set(gca, 'XLim', [0, t_end]); title('input'); subplot(2, 1, 2); plot(kgrid.t_array, sensor_data.p(end/2, :)); set(gca, 'XLim', [0, t_end]); title('output in centre'); Bradley Treeby on "Modelling a 2D simple room(bounded by 4 walls ) with an audible sound source ." http://www.k-wave.org/forum/topic/modelling-a-2d-simple-roombounded-by-4-walls-with-an-audible-sound-source#post-4321 Mon, 17 Feb 2014 22:31:56 +0000 Bradley Treeby 4321@http://www.k-wave.org/forum/ Hi Gurashish, There are many ways you could do this. For example, you could replace the time varying source with an impulsive source by defining <code>source.p0</code> instead of <code>source.p</code>, and then compare the time of arrival between two sensor points spaced some distance apart. If you're having trouble with defining the sensor mask or interpreting the sensor data, I'd suggest taking a looking at the <a href="http://www.k-wave.org/documentation.php">k-Wave Manual</a>. Good luck with your simulations, Brad. Gurashish singh on "Modelling a 2D simple room(bounded by 4 walls ) with an audible sound source ." http://www.k-wave.org/forum/topic/modelling-a-2d-simple-roombounded-by-4-walls-with-an-audible-sound-source#post-4311 Sun, 16 Feb 2014 04:50:23 +0000 Gurashish singh 4311@http://www.k-wave.org/forum/ to validate this model . I m trying to see if the time delay between the signals recieved at two nodes corresponds to the speed of sound in air . ie distance between nodes / time delay . I am not getting the required speed . Is there a way to validate that this model is completely equivalent to a source present in a room , Since i dont want my experimental results to differ extremely from the numerical modelling ? I tried using the Xcorr function to find lag between two signals , but its confusing . P.S : I am Researching on Application of Time Reversal in Localising a Source in Room . So if you have any suggestions regarding some experimentation/modelling it would be interesting to know ! Bradley Treeby on "Modelling a 2D simple room(bounded by 4 walls ) with an audible sound source ." http://www.k-wave.org/forum/topic/modelling-a-2d-simple-roombounded-by-4-walls-with-an-audible-sound-source#post-4308 Fri, 14 Feb 2014 17:42:16 +0000 Bradley Treeby 4308@http://www.k-wave.org/forum/ It seems your source frequency is too high to be supported by the spatial grid. The grid needs to have a least two points per wavelength at the highest frequency of interest, where f_max = c0 / (2 * dx). There's more information about this in the k-Wave manual if you're stuck. Brad. --- <pre><code>clear all; % set the PML size PML_size = 20; % create the computational grid [ 3m by 3m domain ] Nx = 128 - 2*PML_size; % number of grid points in the x (row) direction Ny = 128 - 2*PML_size; % number of grid points in the y (column) direction dx = 3/Nx; % grid point spacing in the x direction [m] dy = 3/Ny; % grid point spacing in the y direction [m] kgrid = makeGrid(Nx, dx, Ny, dy); % define the properties of the propagation medium c_air = 330; % [m/s] rho_air = 1.225; % [kg/m^3] % define the properties of the wall c_wall = 1000; % [m/s] rho_wall = 1000; % [kg/m^3] thickness = 5; % [grid points] % define the position of the wall wall = zeros(Nx, Ny); wall(1:thickness, :) = 1; wall(end - thickness + 1:end, :) = 1; wall(:, 1:thickness) = 1; wall(:, end - thickness + 1:end) = 1; % assign the medium properties medium.sound_speed = c_air*ones(Nx, Ny); medium.sound_speed(wall == 1) = c_wall; medium.density = rho_air*ones(Nx, Ny); medium.density(wall == 1) = rho_wall; % set the reference sound speed used in the k-space operator medium.sound_speed_ref = c_air; % create the time array cfl = 0.1; t_end = 20e-3; % [s] [kgrid.t_array, dt] = makeTime(kgrid, medium.sound_speed, cfl, t_end); % define a time varying sinusoidal source source_freq = 1.5e3; % [Hz] source_mag = 50; % [Pa] source.p = source_mag*toneBurst(1/kgrid.dt, source_freq, 3); % define a single source point source.p_mask = zeros(Nx, Ny); source.p_mask(60, 40) = 1; % define sensors everywhere sensor.mask = ones(Nx, Ny); % define the acoustic parameters to record sensor.record = {'p'}; % run simulation sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor, ... 'PMLInside', false, 'PlotPML', false, 'PMLSize', PML_size, ... 'DisplayMask', 'off', 'PlotScale', [-0.25, 0.25]*source_mag,... 'DataCast', 'single'); % plot the recorded data figure; subplot(2, 1, 1) plot(kgrid.t_array(1:length(source.p)), source.p); set(gca, 'XLim', [0, t_end]); title('input'); subplot(2, 1, 2); plot(kgrid.t_array, sensor_data.p(end/2, :)); set(gca, 'XLim', [0, t_end]); title('output in centre');</code></pre> Gurashish singh on "Modelling a 2D simple room(bounded by 4 walls ) with an audible sound source ." http://www.k-wave.org/forum/topic/modelling-a-2d-simple-roombounded-by-4-walls-with-an-audible-sound-source#post-4307 Fri, 14 Feb 2014 16:41:17 +0000 Gurashish singh 4307@http://www.k-wave.org/forum/ Yes ! i have disabled the PML as well as made the walls realistically thicker , but the recorded signals are not matching the source signal at all . Though what i expect is that the sound signals would hit the concrete walls and reverberate in the room. Recorded signals would atleast have similarity with source . This is exactly what i use . % create the computational grid [ 3m by 3m domain ] Nx = 20; % number of grid points in the x (row) direction Ny = 20; % number of grid points in the y (column) direction dx = 0.15; % grid point spacing in the x direction [m] dy = 0.15; % grid point spacing in the y direction [m] kgrid = makeGrid(Nx, dx, Ny, dy); % define the properties of the propagation medium [ bounded by concrete walls 0.9m thick] medium.sound_speed = 330*ones(Nx, Ny); % [m/s] medium.sound_speed(1:7,:) = 3200; % [m/s] medium.sound_speed(:,1:7) = 3200; medium.sound_speed(:,14:Nx) = 3200; medium.sound_speed(14:Nx,:) = 3200; medium.density = 1.225*ones(Nx, Ny); % [kg/m^3] medium.density(1:7,:) = 2300; % [kg/m^3] medium.density(:,1:7) = 2300; medium.density(14:Nx,:) = 2300; medium.density(:,14:Nx) = 2300; % create the time array % [kgrid.t_array, dt] = makeTime(kgrid, medium.sound_speed); % % define a time varying sinusoidal source % source_freq = 7000; % [Hz] % source_mag = 50; % [Pa] % source.p = source_mag*sin(2*pi*source_freq*kgrid.t_array); % define a single source point source.p_mask = zeros(Nx, Ny); source.p_mask(10,10) = 1; % [ define sensors everywhere ] sensor.mask = ones(Nx, Ny); % define the acoustic parameters to record sensor.record = {'p'}; % layout in addition to removing the PML from the display sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor,'PMLInside', false); Bradley Treeby on "Modelling a 2D simple room(bounded by 4 walls ) with an audible sound source ." http://www.k-wave.org/forum/topic/modelling-a-2d-simple-roombounded-by-4-walls-with-an-audible-sound-source#post-4306 Fri, 14 Feb 2014 11:05:56 +0000 Bradley Treeby 4306@http://www.k-wave.org/forum/ Hi Gurashish, Have you taken into account the perfectly matched layer (PML)? This is a thin layer surrounding the computational grid that absorbs the waves as they reach the edges. In 2D, the default size of the PML is 20 grid points positioned inside the computational grid defined by the user. You can set the PML to be outside the computational grid by setting <code>'PMLInside'</code> to <code>false</code>, i.e., <code>sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor, 'PMLInside', false);</code> Alternatively, you could make your walls fat enough that they extend through the PML and into the interior of the domain, i.e., make them thicker than 20 grid points. Keep in mind your simulation will be fastest when the total grid size including the PML is a number with small prime factors. You can use the function <code>checkFactors</code> to identify suitable values. If you're happy modifying the simulation functions, another way to model the room is suggested in <a href="http://www.k-wave.org/forum/topic/room-enclouse-acoustic-simulation">this post</a>. Hope that helps, Brad. Gurashish singh on "Modelling a 2D simple room(bounded by 4 walls ) with an audible sound source ." http://www.k-wave.org/forum/topic/modelling-a-2d-simple-roombounded-by-4-walls-with-an-audible-sound-source#post-4305 Fri, 14 Feb 2014 02:12:31 +0000 Gurashish singh 4305@http://www.k-wave.org/forum/ Hi , I have to model a "room (2 by 2 m) " in 2-D with a single acoustic source and detect pressure fields at all grid points defined . For now i am using the heterogeneous medium example , inputting density and speed of sound 330m/s,1.225kg/m3 everywhere in the grid except bounding the four edges of grid with density and speed of sound in CONCRETE . I am not able to get any reverberations recorded at sensor points infact recorded signals are decayed . Is this the correct way of constructing the "room" ? panda16 on "simulation using acoustic signal to determine material type in underwater" http://www.k-wave.org/forum/topic/simulation-using-acoustic-signal-to-determine-material-type-in-underwater#post-3376 Fri, 03 May 2013 09:08:07 +0000 panda16 3376@http://www.k-wave.org/forum/ Thanks for the reply bencox on "simulation using acoustic signal to determine material type in underwater" http://www.k-wave.org/forum/topic/simulation-using-acoustic-signal-to-determine-material-type-in-underwater#post-3372 Fri, 03 May 2013 07:34:09 +0000 bencox 3372@http://www.k-wave.org/forum/ Hi panda16, k-Wave currently only models wave propagation in fluids, so it will not model the shear waves in solids, and so the reflection coefficients it models - which is presumably what you are trying to measure - will not be the same as if shear waves were included. An elastic wave code will be released in due course. Kind regards, Ben panda16 on "simulation using acoustic signal to determine material type in underwater" http://www.k-wave.org/forum/topic/simulation-using-acoustic-signal-to-determine-material-type-in-underwater#post-3371 Fri, 03 May 2013 04:28:17 +0000 panda16 3371@http://www.k-wave.org/forum/ Hello, I'm new to the k-wave. Have gone through some example in this forum. Is it possible to perform simulation using acoustic signal to determine the material type in underwater? I will be having an acoustic sensor in underwater located perpendicular to the test object. I would like to use acoustic signal to determine the structural type to see the is the object a plastic, a concrete or something else. Anyone have any idea? Thanks