http://www.k-wave.org/forum/topic/sound-from-ultrasound Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 00:19:55 +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-from-ultrasound#post-4685 Tue, 19 Aug 2014 18:01:51 +0000 Bradley Treeby 4685@http://www.k-wave.org/forum/ <p>Unfortunately I don't have many other suggestions, except for continuing to increase the pressure to see if you see an effect.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/sound-from-ultrasound#post-4682 Tue, 19 Aug 2014 14:52:38 +0000 PiesangBrood2000 4682@http://www.k-wave.org/forum/ <p>Hi Brad,</p> <p>the source pressure was at 2 Pa (peak). I've rerun the simulation with a RMS pressure of 6.5 Pa and it still doesn't seem to indicate any of the nonlinear effects I'm expecting.</p> <p>Kind regards,<br /> PiesangBrood2000 </p> http://www.k-wave.org/forum/topic/sound-from-ultrasound#post-4679 Mon, 18 Aug 2014 17:32:40 +0000 Bradley Treeby 4679@http://www.k-wave.org/forum/ <p>Hi PiesangBrood2000,</p> <p>This sounds like an interesting project. I don't have much experience simulating nonlinear effects in air. However, the contribution of the nonlinear effects will depend on the amplitude of the pressure waves. Wikipedia suggests to generate sound from ultrasound, you need ~110 dbSPL, i.e., the RMS pressure should be 20e-6*10^(110/20) = 6.5 Pa. What pressure do you currently use for your source?</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/sound-from-ultrasound#post-4674 Fri, 15 Aug 2014 08:02:40 +0000 PiesangBrood2000 4674@http://www.k-wave.org/forum/ <p>Hi,</p> <p>I'm trying to simulate a localized sound field in air using the sound from ultrasound techniques (<a href="http://en.wikipedia.org/wiki/Sound_from_ultrasound)" rel="nofollow">http://en.wikipedia.org/wiki/Sound_from_ultrasound)</a>. I've got two ultrasonic sources, one at 20 kHz and one at 21 kHz. Looking at the frequency spectrum of a sensor placed at the point where the two waves meet it does not give the expected result which is a harmonic at the difference frequency of 21 kHz - 20 kHz = 1 kHz.</p> <p>the grid is set up as follows:<br /> c0_min = 343;<br /> f_max = 25e3;<br /> x_size = 1;<br /> y_size = 1;<br /> points_per_wavelength = 2;<br /> dx = c0_min/(points_per_wavelength*f_max);<br /> dy = dx;<br /> Nx = round(x_size/dx);<br /> Ny = round(y_size/dy);<br /> kgrid = makeGrid(Nx, dx, Ny, dy); </p> <p>The medium is set up as follows:<br /> medium.sound_speed = 343;<br /> medium.alpha_coeff = 2.4*10^(-7);<br /> medium.alpha_power = 1.4484;<br /> medium.density = 1.045;<br /> medium.BonA = 0.4;<br /> [kgrid.t_array, dt] = makeTime(kgrid, medium.sound_speed);</p> <p>The sensor data looks like this: <a href="http://imgur.com/T9zuyN4" rel="nofollow">http://imgur.com/T9zuyN4</a></p> <p>A FFT of this data looks like this: <a href="http://imgur.com/ZB2eFQ4" rel="nofollow">http://imgur.com/ZB2eFQ4</a></p> <p>Is it possible to simulate the nonlinear effects with k_wave? If so what am I doing wrong? </p>