http://www.k-wave.org/forum/topic/sound-speed-determination-in-heterogeneous-medium Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 02:33:24 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/sound-speed-determination-in-heterogeneous-medium#post-7937 Thu, 26 Nov 2020 11:17:26 +0000 Bradley Treeby 7937@http://www.k-wave.org/forum/ <p>Hi Ahmet,</p> <p>This suggests that the inverse problem as you've set it up is not well-posed. It may be that you need more complexity in your source, or perhaps more sensor data.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/sound-speed-determination-in-heterogeneous-medium#post-7911 Mon, 02 Nov 2020 18:53:01 +0000 AhmetYildirim 7911@http://www.k-wave.org/forum/ <p>Thank you for your answer. Yes i have tried the algorithm which maximizes the sharpness metric. But the plot i obtained has several peaks close to each other. Also the Normalized Focus Function value of the real sound speed combination is not the one with highest value.</p> <p>When i give the correct sound speeds of 2 of 3 mediums and change the other one through loop and calculate the sharpness, it mostly gives my the correct sound speed of that medium. There is no problem with that.</p> <p>But when i loop all mediums sound speeds and compare sharpness values of all combinations it has a lot close peaks as i mentioned.</p> <p>What could be the reason?</p> <p>As an example:<br /> Real values of sound speeds of mediums are: 1450, 1550, 1600<br /> I created a nested loop and changed sound speeds as 1400:25:1700<br /> The result has peak at almost 15 combination and the highest one is at 1450, 1550, 1400</p> <p>I suppose it is because of the medium with really low thickness compared to the others. Which is the topmost medium. Sharpness decreases when i increase the sound speed assumption of that medium. </p> http://www.k-wave.org/forum/topic/sound-speed-determination-in-heterogeneous-medium#post-7906 Sun, 01 Nov 2020 22:53:00 +0000 Bradley Treeby 7906@http://www.k-wave.org/forum/ <p>Have you tried using a simple optimisation algorithm to find the three sound speeds by maximising the sharpness metric?</p> <p>I recall someone published on this a few years ago, but I don't remember the reference off hand. You could try going through the <a href="https://scholar.google.co.uk/scholar?cites=10304938964631880461&amp;as_sdt=2005&amp;sciodt=0,5&amp;hl=en">citations of the original autofocus paper</a> on google scholar to see if you can find it.</p> <p>Brad </p> http://www.k-wave.org/forum/topic/sound-speed-determination-in-heterogeneous-medium#post-7887 Sun, 25 Oct 2020 13:01:21 +0000 AhmetYildirim 7887@http://www.k-wave.org/forum/ <p>I am trying to make photoacoustic image reconstruction of a heterogenous medium that I've created on k-wave.</p> <p>The properties of this simulated area are basically:<br /> I have 3 mediums with different sound speeds, their density is equal to each other. And i have a binary line sensor on top of these mediums.</p> <p>My aim is to determine the sound speed of each medium and obtain better reconstruction image. I need to make correlation between sound speed of mediums and their thickness. Until now i used Time Reversal reconstruction algorithm given with k-wave toolbox, i got result image of various combination of sound speeds for each medium but it is hard and time consuming to make correlation between thousands of images.</p> <p>There is "Automatic Sound Speed Selection Example" given in k-wave toolbox. I tried to determine sound speeds of the mediums with that but i couldn't achieve any meaningful output (at least for me). I think it is because i have 3 different mediums and a line sensor.</p> <p>So, my question is that am i able to determine the sound speeds of mediums that i have created in k-wave by only having sensor_data as an input? If so how can i do that to determine sound speeds of each medium. </p>