I am just entering the world of propagation modeling and transmission loss estimating and I'm curious about the differences between the MMPE and the Bellhop models. Is there a certain environment where one is better than the other? Does anyone have resources or recommendations of literature I can read to better educate myself? I know there are other propagation models out there too – any info provided about those would be great, but the MMPE and Bellhop are the two that I've come across most often when looking for info.

I understand that the MMPE model is a range-dependent model using a derivation of the wave equation to model transmission loss. I've read that it's appropriate for use in shallow-water environments for low frequency sounds. I've downloaded the program and intro/instructions for using the MMPE also.

I've found a similar set of documents for the Bellhop model - both the manual and user guide and a brief overview of how it's used, but I was hoping someone could help explain in simpler terms what the key differences are and in what environments you would use one or the other.

For example, if my recording site is in the middle of a canyon like the Monterey Canyon, which model would be better to use? I would think Bellhop because of the deep water associated with the canyon. Or would this require a more sophisticated model given the relatively complex bathymetry associated with the canyon?


2 Answers 2


Bellhop is a ray tracing approach, while MMPE is a parabolic estimation. Definitely check out the acoustic toolbox and the documentation suggested above. RAM/RAMGEO is another parabolic equation model that is widely used and may have more documentation than MMPE. Kraken is a normal mode model. Each type of model has pros and cons for different environments and frequencies. So you would want to figure out the environment that you want to model TL for, e.g. range dependent or range independent; depth etc., and the frequency of acoustic pressure of interest. As an example, bellhop and ray tracing may not be appropriate for low-frequency sounds but may be fine for higher frequency sounds.


I would strongly suggest to inspect the Acoustic Toolbox website and read the comments, explanations of the different programs. I understand there are different dialects of PE programs, but they are all similar.

Download the toolbox and run the different test cases to get a taste about them.


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