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This example shows how k-Wave can be used to model the output of a focussed bowl detector where the directionality arises from spatially averaging across the detector surface. It builds on the Homogeneous Propagation Medium and Using A Binary Sensor Mask examples.
For large single element detectors, the directionality arises
because the output is spatially averaged across the pressure field on
the transducer surface. Here this effect is simulated using a focussed
bowl detector (defined using a binary sensor mask) created with makeCircle
.
% define a sensor as part of a circle centred on the grid
sensor_radius = 65; % [pixels]
arc_angle = pi; % [rad]
sensor.mask = makeCircle(Nx, Nz, Nx/2, Nz/2, sensor_radius, arc_angle);
To illustrate the directionality of the simulated detector, a disc
shaped source (created using makeDisc
) is
first placed at the focus of the detector and then horizontally offset.
A visualisation of the two simulations (with the initial pressure
distribution overlayed) is given below.
The output from the simulated single element detector is then
obtained by averaging the time signals recorded at each pixel within
the sensor.mask
giving a single time series output. The
resulting time series for both source positions are shown below; it is
clear that the detector produces a larger output for the source nearer
the focus of the detector. (This example uses an initial value as the
source of the wave, but this averaging effect will also be seen for
time-varying sources.)
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Sensor Directivity | Focussed Detector in 3D | ![]() |
© 2009, 2010, 2011 Bradley Treeby and Ben Cox.