Which term refers to a low-frequency filter used in signal processing?

• A. High Pass Filter
• B. Bandpass Filter
• C. Notch Filter
• D. Low Frequency Filter

Answer: (D)

In signal processing, filters shape which frequencies of a signal are allowed to pass. A low-pass filter is designed to pass frequencies below a certain cutoff with little attenuation while progressively attenuating frequencies above that cutoff. This exact behavior—letting low frequencies through while suppressing higher ones—defines it as the term for a filter that targets low-frequency content.

The phrase “low frequency filter” isn’t the standard name for this type. It’s vague and could refer to many different implementations, whereas the proper, widely used designation is low-pass filter.

To contrast, a high-pass filter does the opposite by attenuating low frequencies and passing higher ones; a bandpass filter passes only a specific range of frequencies; and a notch (band-stop) filter attenuates a narrow range around a particular frequency.