Which one or more of the following statements is true regarding notch filters?

Notch filters are designed to eliminate specific frequency components from a signal, commonly associated with power line interference, such as the 60-Hz frequency in the United States. While they can be helpful in reducing noise and interference in EEG and EMG recordings, excessive use of these filters can obscure important information in the signal.

The accuracy of the option stating that notch filters should not be used routinely in EEG recordings stems from the understanding that applying these filters regularly might mask underlying issues within the data. For instance, a bad signal or an unstable electrical environment could go undetected if a notch filter is incorrectly applied. This can compromise the quality of the analysis and lead to misinterpretation of the results.

Additionally, it is correct that notch filters should only be employed when absolutely necessary. The decision to utilize such filters typically occurs when there is clear evidence of unwanted interference—like minor 60-Hz noise—and after assessing the impact on the overall signal. Employing notch filters judiciously ensures that the integrity of the recorded data remains intact while mitigating interference effectively.

Therefore, the statements that highlight the cautious use of notch filters and the consideration of their impact on signal quality provide a valid context for their application, thus supporting the choice that both statements B and C