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.