http://www.k-wave.org/forum/topic/swapability-of-impulse-source-and-sensor Support for the k-Wave MATLAB toolbox en-US Tue, 12 May 2026 23:40:50 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/swapability-of-impulse-source-and-sensor#post-499 Wed, 09 May 2012 03:42:54 +0000 Bradley Treeby 499@http://www.k-wave.org/forum/ <p>Hi Chesteta,</p> <p>You should get the same thing directly. Here's a simple example to try:</p> <p>clear all;</p> <p>% create the computational grid<br /> PML_size = 20;<br /> Nx = 128 - 2*PML_size;<br /> Ny = 128 - 2*PML_size;<br /> dx = 0.1e-3;<br /> dy = 0.1e-3;<br /> kgrid = makeGrid(Nx, dx, Ny, dy);</p> <p>% define the properties of the propagation medium<br /> medium.sound_speed = 1500 + (rand(Nx, Ny) - 0.5)*300;<br /> medium.density = medium.sound_speed./1.5;</p> <p>% define initial pressure distribution and binary sensor mask<br /> p0 = zeros(Nx, Ny);<br /> p0(Nx/4, Ny/4) = 1;<br /> sensor_mask = zeros(Nx, Ny);<br /> sensor_mask(3*Nx/4, 3*Ny/4) = 1;</p> <p>% set simulation options<br /> input_args = {'LogScale', true, 'DisplayMask', p0 | sensor_mask, ...<br /> 'PMLInside', false, 'PlotPML', false};</p> <p>% assign the source and sensor and run the simulation<br /> source.p0 = p0;<br /> sensor.mask = sensor_mask;<br /> sensor_data_12 = kspaceFirstOrder2D(kgrid, medium, source, sensor, input_args{:});</p> <p>% switch the source and sensor and run the simulation again<br /> source.p0 = sensor_mask;<br /> sensor.mask = p0;<br /> sensor_data_21 = kspaceFirstOrder2D(kgrid, medium, source, sensor, input_args{:});</p> <p>% plot the impulse response<br /> figure;<br /> plot(sensor_data_12, 'k-');<br /> hold on;<br /> plot(sensor_data_21, 'r--');<br /> legend('Impulse Response P1 to P2', 'Impulse Response P2 to P1');</p> <p>Kind regards,</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/swapability-of-impulse-source-and-sensor#post-487 Wed, 02 May 2012 00:44:35 +0000 Chesteta 487@http://www.k-wave.org/forum/ <p>Thanks for the info! Will I get the same impulses directly, or do I need to do additional processing? </p> http://www.k-wave.org/forum/topic/swapability-of-impulse-source-and-sensor#post-481 Tue, 01 May 2012 01:15:05 +0000 Bradley Treeby 481@http://www.k-wave.org/forum/ <p>Hi Chesteta,</p> <p>The term you're looking for is "reciprocity", and the answer is yes. In fact, this idea is already used both experimentally and computationally to derive HRTFs. Two relevant references are <a href="http://asadl.org/jasa/resource/1/jasman/v120/i4/p2202_s1">here</a> and <a href="http://asadl.org/jasa/resource/1/jasman/v119/i5/p2589_s1">here</a>.</p> <p>Good luck with your simulations!</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/swapability-of-impulse-source-and-sensor#post-480 Tue, 01 May 2012 00:30:26 +0000 Chesteta 480@http://www.k-wave.org/forum/ <p>Hello, this is more of a 'general wave theory' question:<br /> I am trying to create head-related transfer functions (impulse responses) using CT scan data of my head, by setting a point source of pressure and measuring within the ear canal of the model. I figure it would be more computationally efficient to reverse the process and use many sensors placed around the head and create an impulse inside of the ear (so I can measure impulse responses from many angles at once), does this 'work' on the physics side of things?</p> <p>More plainly: can one swap an impulse source and the sensor in the model and achieve the same impulse response? - if not the same impulse response, would the frequency response at least be the same? </p> <p>From setting up sub-woofers, I know that one way to do it is to set the sub-woofer in the listening position and then crawl around and find where the bass 'sounds good' (has an even frequency response) - my thinking is that this applies to all frequencies...</p> <p>Thanks for your knowledge and help! </p>