Add transient and impulse noise masks

[beatfactor]

Overview

This PR introduces two new functions, get_impulse_noise_mask and get_transient_noise_mask that provide masks for impulsive noise (noise sources shorter than 1 ping) and transient noise (short, but still multi-ping noise sources). These are ported from the echopy library:
mask_impulse.py
mask_transient.py

Methodologies

The methodology employed uses both previously published methods defined:

• Reducing bias due to noise and attenuation in open-ocean echo integration. ICES Journal of Marine Science 72, 2482-2493 – Ryan T. E., Downie R. A., Kloser R. J., Keith G. (2015) (ryan as mask generation method)
• A noise removal algorithm for acoustic data with strong interference based on post-processing techniques CCAMLR SG-ASAM: 15/02 – Wang et al. (2015) (wang, for impulse noise only - unlike in echopy, this has been modified to provide a mask rather than a modified Sv array).
• otherwise-unpublished methods implemented by the authors of echopy (fielding as mask-generation method, for transient noise only).

Key Features

1. Impulse noise - implements the Ryan two-sided comparison method as "ryan", an iterable modification of it that allows it to detect adjacent noise spikes, and the Wang erosion/dilation/median filtering method as "wang"
2. Transient noise - implements the Ryan identified Sv spikes method as "ryan" and a previously unpublished method proposed by Fielding et al, which compares the data, ping by ping, with respect to a bloc in a reference layer – should the ping median be greater than the block median by a user-defined threshold, the ping will be masked until transient noise disappears or until it gets to the minimum range allowed by the user

Key Considerations

In order to ensure compatibility between the echopy and echopype libraries, several important factors were taken into account while adapting the echopy code – responsible for noise masking:

• Data type discrepancies: the differences in input and output data types between the two libraries required adjustment.
• Mask delivery variation: in echopy, two separate masks are typically generated: one indicating the locations of noise (represented as true) and another showing where the method applied may not have been suitable for certain samples. In contrast, echopype usually delivers a single mask marking samples that are free of noise.
• Differences in the ‘pings’ and ‘range’ axes: the two libraries have divergent approaches to these axes, which needed to be addressed.

For each noise type, specific decisions were made to combine and adapt the masks appropriately within the echopype environment.

Function Signatures

def get_impulse_noise_mask(
    source_Sv: xr.Dataset,
    desired_channel: str,
    thr: Union[Tuple[float, float], int, float],
    m: Optional[Union[int, float]] = None,
    n: Optional[Union[int, Tuple[int, int]]] = None,
    erode: Optional[List[Tuple[int, int]]] = None,
    dilate: Optional[List[Tuple[int, int]]] = None,
    median: Optional[List[Tuple[int, int]]] = None,
    method: str = "ryan",
) -> xr.DataArray:

def get_transient_noise_mask(
    source_Sv: Union[xr.Dataset, str, pathlib.Path],
    desired_channel: str,
    mask_type: str = "ryan",
    **kwargs
) -> xr.DataArray:

Usage

The functions can be utilised to create masks for Sv data based on identified single-ping or short multi-ping noise sources.

[codecov-commenter]

Codecov Report

Merging #1142 (ec60163) into dev (6b734eb) will decrease coverage by 9.89%.
Report is 49 commits behind head on dev.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##              dev    #1142      +/-   ##
==========================================
- Coverage   80.71%   70.82%   -9.89%     
==========================================
  Files          67       10      -57     
  Lines        6056     1042    -5014     
==========================================
- Hits         4888      738    -4150     
+ Misses       1168      304     -864     

Flag	Coverage Δ
unittests	70.82% <77.77%> (-9.89%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
echopype/utils/mask_transformation.py	62.99% <62.99%> (ø)
echopype/mask/mask_transient_noise.py	90.00% <90.00%> (ø)
echopype/mask/mask_impulse_noise.py	99.12% <99.12%> (ø)
echopype/mask/__init__.py	100.00% <100.00%> (ø)

... and 66 files with indirect coverage changes

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[beatfactor]

Codecov Report

@mihaiboldeanu Looks like we could do a with a few more tests.

[leewujung]

Hey folks, thanks for the PR!

I did a high-level review of the function/module organization and have the following suggestions. @emiliom also contributed to the discussion.

• Could you please revert all the changes in tests/mask/test_mask.py? These changes are due to formatting, and even though the current one is not optimal, this would cause conflicts for the ongoing other PR Improved input syntax for frequency_differencing operation #1106 .
• Based on what we have for the subpackage organization (see here), these noise mask generation functions would be in the clean subpackage. It is true that the functions you added here are generating masks, but noise assessment is a pretty central task for data processing that having its own subpackage is logical. So, could you move them? In the comment below I'll use clean to avoid confusion, but let me know if it is confusing!
• Could you use pytest fixtures for the setup parts of the two test modules test_mask_transient.py and test_mask_impulse_noise.py, and put them in tests/clean/conftest.py so that they can be reused in the test modules. Also suggest renaming:
  • test_mask_transient.py to test_clean_transient_noise.py
  • test_mask_impulse_noise.py to test_clean_transient_noise.py
• For get_impulse_noise_mask.py:
  • move the function get_impulse_noise_mask to within echopype/clean/api.py
  • move all the subfunctions (ryan, ryan_iterable, wang, etc) to a separate module echopype/clean/impulse_noise.py, and add _ to the beginning of the function call so it is clear they are private functions
• For get_transient_noise_mask.py:
  • move the function get_transient_noise_mask to within echopype/clean/api.py
  • move the other two functions _get_transient_noise_mask_ryan and _get_transient_noise_mask_fielding to a separate module echopype/clean/transient_noise.py, and rename them to just _ryan and _fielding

For the last 2 points, our convention has been to keep the main API call under a subpackage in subpackage/api.py, and put supporting functions into separate modules (.py files) with filenames indicating which api function they are used in.

In addition, in clean we currently only have one function with a generic name (remove_noise), even though that function implements a specific algorithm that aims to estimate the time-varying background noise. With your addition of new noise removal functions (once masked), we need to change this function name and figuring out the API pattern for noise-related functions that generate masks (like these added here) and functions that suppress some noise (the current remove_noise). But all that would be a separate PR.

[ruxandra-valcu]

Hello @leewujung

I've rewritten this PR (both the already-reviewed impulse noise algorithms and the transient noise and signal attenuation ones) to use xarray functionality rather than numpy.

Please let me know if there are any other improvements I should make!

[ctuguinay]

Closing this since the Echopy functions were added in #1316 and #1326