Which filter is typically used to remove power line electrical noise?

Which filter is typically used to remove power line electrical noise?

• A. Low frequency filter
• B. Brita filter
• C. Notch (60 hz) filter
• D. High-frequency filter

Answer: (C)

Power line interference shows up as a narrow, near-pure tone at the mains frequency (typically 60 Hz in the U.S., 50 Hz in many other regions). To remove that specific noise without distorting the rest of the signal, a notch filter is used. This is a narrowband stop filter centered around 60 Hz that sharply attenuates that one frequency while leaving neighboring frequencies largely intact. That preserves the important slow and fast components of the sleep signals, unlike a low-frequency filter (which would distort slow trends) or a high-frequency filter (which would remove rapid details). A Brita filter is not relevant to electrical filtering.

Power line interference shows up as a narrow, near-pure tone at the mains frequency (typically 60 Hz in the U.S., 50 Hz in many other regions). To remove that specific noise without distorting the rest of the signal, a notch filter is used. This is a narrowband stop filter centered around 60 Hz that sharply attenuates that one frequency while leaving neighboring frequencies largely intact. That preserves the important slow and fast components of the sleep signals, unlike a low-frequency filter (which would distort slow trends) or a high-frequency filter (which would remove rapid details). A Brita filter is not relevant to electrical filtering.