Skip to content

Remove harmonic artefacts from wavelet spectrograms.

License

Notifications You must be signed in to change notification settings

lwiklendt/mesaclip

Folders and files

NameName
Last commit message
Last commit date

Latest commit

 

History

20 Commits
 
 
 
 
 
 
 
 
 
 
 
 

Repository files navigation

An O(n) algorithm for clipping wide peaks from 1D signals, designed for application to removing harmonic artefacts from the continuous wavelet transform.

Published in the open-access article: https://www.frontiersin.org/articles/10.3389/fphys.2020.00484/full

Given a signal with amplitudes y[0..n-1] and non-decreasing locations x[0..n-1], clips all peaks that are too wide x[b] - x[a] > k for all b > a and given parameter k.

The following animation shows an example with a uniformally increasing x along the horizontal, y along the vertical, and k = 12:

The mesaclip.py file contains the main algorithm in the mesaclip function, and demo.py will reproduce the animation. Running the mesaclip.py file will run tests on random signals.

The following table shows four examples comparing a convential continuous wavelet transform and one with mesaclipping applied. The middle subplots use a conventional Morse(β=12, γ=3) wavelet transform, and the bottom subplots use a Morse(β=1.58174, γ=3) wavelet with mesaclipping applied. The mesaclipped version does not suffer from harmonic artefacts generated due to sharp changes in the singals.

From a smooth to a spiky signal Bursts of Dirac deltas
Thresholded chirp Real EMG signal

The choice of β=1.58174 is based on minimising the 1st harmonic amplitude of a Dirac comb halfway between two Dirac delta functions:

Example applications to some real EMG data:

Exploration of signal-to-noise ratio for artificial spike-train signals of varying regularity:

Estimates of the ground truth frequency:

About

Remove harmonic artefacts from wavelet spectrograms.

Resources

License

Stars

Watchers

Forks

Releases

No releases published

Packages

No packages published

Languages