Bellhop
Model AcousticsToolbox.Bellhop
Description Bellhop ray/beam tracer (wrapper)
Language Fortran
Advantages Well-established benchmark model
Limitations Not differentiable, 2½D or 3D modeling not supported 
Bellhop(env; kwargs...)

Create a Bellhop propagation model.

Supported keyword arguments:

  • nbeams: number of beams to use (default: 0, auto)
  • min_angle: minimum beam angle (default: -80°)
  • max_angle: maximum beam angle (default: 80°)
  • beam_type: geometric (default) or gaussian
  • beam_shift: use beam shift (default: false)
  • debug: debug mode (default: false)

Enabling debug mode will create a temporary directory with the Bellhop input and output files. This allows manual inspection of the files.

A good overview of the Bellhop model can be found at:

Example

using UnderwaterAcoustics
using AcousticsToolbox
using Plots

env = UnderwaterEnvironment(
  bathymetry = SampledField([200, 150]; x=[0, 1000], interp=Linear()),
  soundspeed = SampledField([1500, 1480, 1495, 1510, 1520]; z=0:-50:-200, interp=CubicSpline()),
  seabed = SandyClay
)
pm = Bellhop(env)

tx = AcousticSource(0, -50, 300)
rx = AcousticReceiver(1000, -100)
rays = arrivals(pm, tx, rx)

plot(env; xlims=(-10, 1010))
plot!(tx)
plot!(rx)
plot!(rays)
rxs = AcousticReceiverGrid2D(1:1000, -200:0)
x = transmission_loss(pm, tx, rxs; mode=:semicoherent)

plot(rxs, x; crange=70)
plot!(env; xlims=(0,1000), linewidth=3)

Notes

The Fortran Bellhop propagation model requires that the transmitter is located at \((x=0, y=0)\) and all receivers are located in the right half-plane (i.e., \(x>0\) and \(y=0\)). While this limitation can be worked around in the wrapper by a coordinate transformation, automatic transformation is not yet implemented.

Additionally, this wrapper does not yet support all the features of the original Fortran model. In particular, it does NOT support:

  • 3D environments (i.e., Bellhop 3D)
  • Range-dependent sound speed
  • N2-linear, analytic or quadratic interpolation for sound speed
  • Arbitrary reflection coefficients
  • Directional or line sources
  • Cartesian or ray-centered beams

Receivers on an irregular grid are supported, but not currently optimized for speed (by using the irregular grid option in the Fortran model).