Boundary conditions / multiple dependet PDE (coefficient form)

Hey there,

I am using the PDE coefficient form with 5 variables (u1, u2, u3, T, p) to solve a thermoacoustic problem in comsol.

I want to implement the following BC to the whole geometry (sound hard, no-slip and isothermal).

Dirichlet BC:

u1 = 0
u2 = 0
u3 = 0
T = 293.15 [K]

Neumann BC:

n*nabla p = 0

How can I implement the Neumann BC? Are there any examples?

Thank you!