Butterworth vs Bessel DSP bandpass filters

dschoepf · October 2015

I was just wondering why the Butterworth filter was selected for all filtering in the EEG Processing. I imagine the maximally flat frequency response is the enviable characteristic, but wouldn't a Bessel filter be preferable in most applications since it tends to preserve the shape of the wave in the pass band region the best? Has anyone had any experience with altering the filters (I'm more interested in filter type than simply band pass). While I grant that it is simple to modify the coefficients of a filter to achieve other forms, I was simply curious as to why the Butterworth filter is the default. Is it industry standard?

wjcroft · October 2015

I can't speak for all applications, but Butterworth is by far used more often in realtime neurofeedback applications.

https://www.google.com/search?q=eeg+butterworth+vs+chebyshev+vs+bessel

https://books.google.com/books?id=hfjSVIWViRUC&pg=RA1-PA304

Some of the apps such as Bioexplorer or BioEra will let you draw a graph of the Delay factor in milliseconds against the incoming frequency of the filter you are setting up. In such cases Butterworth usually is computed faster, which is important if you are looking for realtime feedback with minimal delay. The order of the filter is a very important factor as well.

William

dschoepf · October 2015

Thanks for the response, William! I figured there was some reason that a Butterworth was used besides the fact that MATLAB has a more robust Butterworth function than it does a Bessel. I may look into this further and try to do a comparison of the performance and waveforms obtained using each filter, but I'm glad that I now know that the Butterworth is more standard.

Butterworth vs Bessel DSP bandpass filters

Comments