Example Application
Suppose a hospital is recording a heart beat (an ECG), which is being corrupted by a 50 Hz noise (the frequency coming from the power supply in many countries). However, due to slight variations in the power supply to the hospital, the noise signal may contain harmonics of the noise and the exact frequency of the noise may vary.
One way to remove the noise is to filter the signal with a notch filter at 50 Hz. Such a static filter would need to remove all the frequencies in the vicinity of 50 Hz, which 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 power supply directly and would thus be able to track the actual frequency of the noise as it fluctuates. Such an adaptive technique generally allows for a filter with a smaller rejection range, which means, in our case, that the quality of the output signal is more accurate for medical diagnoses.
Read more about this topic: Adaptive Filter
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