I'm simulating a transducer used as sensor for photoacoustic signals in a 3D setup. Here is my setup:
kWaveGrid with properties:
Nx: 304.0000e+000
Ny: 748.0000e+000
Nz: 12.0000e+000
dx: 170.0000e-006
dy: 170.0000e-006
dz: 170.0000e-006
kx_vec: [304x1 double]
ky_vec: [748x1 double]
kz_vec: [12x1 double]
k: [304x748x12 double]
kx_max: 18.4800e+003
ky_max: 18.4800e+003
kz_max: 18.4800e+003
k_max: 18.4800e+003
dim: 3.0000e+000
nonuniform: 0
t_array: [1x1511 single]
x: [304x748x12 double]
y: [304x748x12 double]
z: [304x748x12 double]
kx: [304x748x12 double]
ky: [304x748x12 double]
kz: [304x748x12 double]
x_vec: [304x1 double]
y_vec: [748x1 double]
z_vec: [12x1 double]
kWaveTransducer with properties:
number_elements: 128.0000e+000
element_width: 5.0000e+000
element_length: 6.0000e+000
element_spacing: 0.0000e+000
position: [6.0000e+000 55.0000e+000 4.0000e+000]
radius: Inf
active_elements: [128x1 double]
elevation_focus_distance: Inf
transmit_apodization: 'Rectangular'
receive_apodization: 'Rectangular'
sound_speed: 1.5289e+003
focus_distance: Inf
record_start_index: 1.0000e+000
active_elements_mask: [304x748x12 uint8]
indexed_active_elements_mask: [304x748x12 uint8]
all_elements_mask: [304x748x12 uint8]
indexed_elements_mask: [304x748x12 uint8]
mask: [304x748x12 uint8]
transducer_width: 640.0000e+000
number_active_elements: 128.0000e+000
steering_angle_max: 'auto'
appended_zeros: 'auto'
beamforming_delays_offset: 'auto'
steering_angle: 0.0000e+000 x_size: 51.6800e-003
z_size: 2.0400e-003
y_size: 127.1600e-003
dt: 33.3575e-009
Nt: 1.5110e+003
total_grid_points: 2.7287e+006
medium =
sound_speed: 1.5289e+003
alpha_coeff: 750.0000e-003
alpha_power: 1.5000e+000
>> find(source.p0)
ans =
1250594
>> [x y z]=ind2sub(size(source.p0),find(source.p0))
x =
242
y =
374
z =
6
An initial value of 1 KPa is applied to the source grid point. The leading edge of the wave should arrive at the farthest sensor in ~43.5 usec and the time trace of that element indeed shows that pulse as expected with a peak ~0.3 Pa.
But, there is another, small blip at ~36.1 usec with amplitude ~3.5% of the expected pulse.
Am I doing something wrong? Is a source with only one grid point not allowed?
I have run this both with/without GPU and in single and double precision all with the same results.