Editing Adaptive filter (section)

==Example application==
The recording of a heart beat (an [[ECG]]), may be corrupted by noise from the [[power supply|AC mains]]. The exact frequency of the power and its [[harmonics]] may vary from moment to moment.

One way to remove the noise is to filter the signal with a [[notch filter]] at the mains frequency and its vicinity, but this could excessively degrade the quality of the ECG since the heart beat would also likely have frequency components in the rejected range.

To circumvent this potential loss of information, an adaptive filter could be used. The adaptive filter would take input both from the patient and from the mains and would thus be able to track the actual frequency of the noise as it fluctuates and subtract the noise from the recording. Such an adaptive technique generally allows for a filter with a smaller rejection range, which means, in this case, that the quality of the output signal is more accurate for medical purposes.<ref>{{Cite journal|title = Applications of adaptive filtering to ECG analysis: noise cancellation and arrhythmia detection|journal = IEEE Transactions on Biomedical Engineering|date = 1991-08-01|issn = 0018-9294|pages = 785–794|volume = 38|issue = 8|doi = 10.1109/10.83591|pmid = 1937512|first1 = N.V.|last1 = Thakor|first2 = Yi-Sheng|last2 = Zhu| s2cid=11271450 }}</ref><ref name="Widrow">{{cite book|last1=Widrow |first1=Bernard |last2= Stearns|first2= Samuel D. |year= 1985 |title=Adaptive Signal Processing |url=https://archive.org/details/adaptivesignalpr00widr |url-access=limited |edition= 1st | page = [https://archive.org/details/adaptivesignalpr00widr/page/n173 329]| publisher= Prentice-Hall|isbn= 978-0130040299 }}</ref>