AcFDTD.jl

3D Room Acoustics Finite Difference Time Domain (FDTD) Simulator
Author nantonel
Popularity
13 Stars
Updated Last
7 Months Ago
Started In
March 2015

AcFDTD (this library is unmantained)

Finite Difference Time Domain (FDTD) method for room acoustic simulation

Installation

From the Julia command line hit:

Pkg.clone("https://github.com/nantonel/AcFDTD.jl.git")

Once the package is installed you can update it along with the others issuing Pkg.update() in the command line.

Usage

Import the package by typing using AcFDTD. First you need to specify an acoustic environment and FDTD scheme:

using AcFDTD
X = 0.1                   # spatial sampling
env = FDTDEnv(X,IISO())   # create new acoustic env with default values

where IISO() returns the Interpolated Isotropic scheme. Alternatively one can choose a samplng frequency instead of a spatial sampling:

Fs = 2000.                          # sampling frequency in Hz
env = FDTDEnv(IISO(),Fs; c = 340)   # create new acoustic env with default values

notice that in the latter line the speed of sound was chosen to be 340 m/s. By default this is set to 343 m/s. Set the acoustic impedance ξ and room geometry room geometry:

ξ = [50.;50.;100.;30.;50.;50.]; # [   ξx1    ;    ξx2   ;    ξy1   ;    ξy2    ;  ξz1 ;   ξz2  ]
                                # [front wall; rear wall; left wall; right wall; floor; ceiling]
geo = CuboidRoom(10, 11, 12, ξ, env)

The first three parameters indicate the number of spatial samples of the x, y and z directions.
Alternatively one can specify the room dimensions in meters:

geo = CuboidRoom(4., 5., 3., ξ, env)

which are then approximated on the grid. Set the number of time steps Nt Create a band-limited sound source with e.g. the DSP package:

using DSP
Nt = round(Int,env.Fs)         # number of time steps (1 sec)
s = zeros(Nt)                    # source signal
s[3] = 1
f2 = geo.env.Fs/2*0.175          # cut-off frequency of source
filt!(s,digitalfilter(Bandpass(10,f2;fs = geo.env.Fs),Butterworth(5)),s)

Define the position of microphone and sound sources:

xr = [(2, 2, 2), (2, geo.Ny-1, geo.Nz-1)] # mic positions
xs = (geo.Nx-1, geo.Ny-1, geo.Nz-1) # sound source position
#positions must be Tuple{Int,Int,Int} or Array{Tuple{Int,Int,Int},1} 

Now type:

p = fdtd(xr,xs,Nt,geo,s)

to obtain the sound pressure of the microphones.

For more details on the methods type:

?fdtd

Credits

AcFDTD.jl is developed by Niccolò Antonello at KU Leuven, ESAT/Stadius.