Hi,

I am trying to simulate the wave propagation in a viscoelastic medium using "pstdElastic2D" function. I assume that the viscoelastic properties can be defined using "medium.alpha_coeff_shear". For a 4 MHz transducer, I am defining the "medium.alpha_coeff_shear" of the order of 1e7 to have a shear viscosity (eta) of 2.5 Pa.s based on the calculation of "eta" in the "pstdElastic2D" function, which is:

```
eta = 2 * rho0 .* medium.sound_speed_shear .^ 3 .*
db2neper(medium.alpha_coeff_shear, 2);
```

However, I don't see any change in the results if I don't define "medium.alpha_coeff_shear" at all (elastic medium). Could you please clarify how the viscoelastic properties can be defined and what the range of "medium.alpha_coeff_shear" should be for a 4 MHz transducer?

Thanks in advance for your time and help.

```
shear_modulus = 4e3; %[Pa]
shear_viscosity = 2.5; %[Pa.s]
medium.density = 1000; % [kg/m^3]
medium.sound_speed_compression = 1540; %[m/s]
medium.sound_speed_shear = sqrt(shear_modulus / medium.density); %[m/s]
medium.alpha_coeff_shear = shear_viscosity /
(2 * medium.density * medium.sound_speed_shear^3) *
8.7 / 100 * (2 * pi * 1e6)^2; %[dB/(MHz^2 cm)]
```