k-Wave User Forum » Topic: Sound pressure decrease with distance

k-Wave User Forum » Topic: Sound pressure decrease with distance http://www.k-wave.org/forum/topic/sound-pressure-decrease-with-distance Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 03:45:11 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php Bradley Treeby on "Sound pressure decrease with distance" http://www.k-wave.org/forum/topic/sound-pressure-decrease-with-distance#post-8005 Tue, 19 Jan 2021 19:50:21 +0000 Bradley Treeby 8005@http://www.k-wave.org/forum/ Hi Andreas, I haven't run your simulation, but in 2D, a point source actually corresponds to an infinite line source so will generate a cylindrical wave (everything is implicitly extended off to infinity in the out-of-plane direction). This means the pressure should decay with 1/sqrt(r). Have a look at the <a href="http://www.k-wave.org/documentation/example_ivp_photoacoustic_waveforms.php">Photoacoustic Waveforms in 1D, 2D and 3D Example</a> if you need more details. Brad Andreas Blum on "Sound pressure decrease with distance" http://www.k-wave.org/forum/topic/sound-pressure-decrease-with-distance#post-7980 Tue, 08 Dec 2020 12:37:11 +0000 Andreas Blum 7980@http://www.k-wave.org/forum/ Hey there, i'm working on a little sound simulation for loudspeakers. With a point source, shouldn't the sound pressure level decrease linear with increasing distance from the source (p ~ 1 / r)? I've attached an little example: Sensor 1 is in 30*dx distance from source Sensor 2 in in 60*dx distance from source The results are: max Pressure Sensor 1: 0.1751 Pa max Pressure Sensor 2: 0.12383 Pa but they dont match with p2 = p1*(r1/r2) = 0.1751*(30/60) = 0,0876 Pa Can someone help me? Best regards Andreas EXAMPLE: % Monopole Point Source In A Homogeneous Propagation Medium Example % % This example provides a simple demonstration of using k-Wave for the % simulation and detection of a time varying pressure source within a % two-dimensional homogeneous propagation medium. It builds on the % Homogeneous Propagation Medium and Recording The Particle Velocity % examples. % % author: Bradley Treeby % date: 2nd December 2009 % last update: 4th May 2017 % % This function is part of the k-Wave Toolbox (<a href="http://www.k-wave.org" rel="nofollow">http://www.k-wave.org</a>) % Copyright (C) 2009-2017 Bradley Treeby % This file is part of k-Wave. k-Wave is free software: you can % redistribute it and/or modify it under the terms of the GNU Lesser % General Public License as published by the Free Software Foundation, % either version 3 of the License, or (at your option) any later version. % % k-Wave is distributed in the hope that it will be useful, but WITHOUT ANY % WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS % FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for % more details. % % You should have received a copy of the GNU Lesser General Public License % along with k-Wave. If not, see <http://www.gnu.org/licenses/>. clearvars; % ========================================================================= % SIMULATION % ========================================================================= % create the computational grid Nx = 128; % number of grid points in the x (row) direction Ny = 128; % number of grid points in the y (column) direction dx = 50e-3/Nx; % grid point spacing in the x direction [m] dy = dx; % grid point spacing in the y direction [m] kgrid = kWaveGrid(Nx, dx, Ny, dy); % define the properties of the propagation medium medium.sound_speed = 343; % [m/s] medium.alpha_coeff = 0;%0.75; % [dB/(MHz^y cm)] medium.alpha_power = 0;%1.5; % create the time array kgrid.makeTime(medium.sound_speed); % define a single source point source.p_mask = zeros(Nx, Ny); source.p_mask(end - Nx/4, Ny/2) = 1; xpos_source = Nx- Nx/4; % define a time varying sinusoidal source source_freq = 0.25e6; % [Hz] source_mag = 2; % [Pa] source.p = source_mag * sin(2 * pi * source_freq * kgrid.t_array); source.p_mode = 'dirichlet'; % filter the source to remove high frequencies not supported by the grid source.p = filterTimeSeries(kgrid, medium, source.p); % define a single sensor point sensor.mask = zeros(Nx, Ny); xpos_sensor_1 = xpos_source - 30; xpos_sensor_2 = xpos_source - 60; sensor.mask(xpos_sensor_1, Ny/2) = 1; sensor.mask(xpos_sensor_2, Ny/2) = 1; % define the acoustic parameters to record sensor.record = {'p', 'p_final'}; %% run the simulation sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor); %% % ========================================================================= % VISUALISATION % ========================================================================= % plot the final wave-field figure; imagesc(kgrid.y_vec * 1e3, kgrid.x_vec * 1e3, ... sensor_data.p_final + source.p_mask + sensor.mask, [-1, 1]); colormap(getColorMap); ylabel('x-position [mm]'); xlabel('y-position [mm]'); axis image; % plot the simulated sensor data figure; [t_sc, scale, prefix] = scaleSI(max(kgrid.t_array(:))); subplot(2, 1, 1); plot(kgrid.t_array * scale, source.p, 'k-'); xlabel(['Time [' prefix 's]']); ylabel('Signal Amplitude'); axis tight; title('Input Pressure Signal'); subplot(2, 1, 2); plot(kgrid.t_array * scale, sensor_data.p, 'r-'); xlabel(['Time [' prefix 's]']); ylabel('Signal Amplitude'); axis tight; title('Sensor Pressure Signal'); disp(['max Pressure Sensor 1: ', num2str(max(sensor_data.p(2,:)))]); disp(['max Pressure Sensor 2: ', num2str(max(sensor_data.p(1,:)))]);