What type of filter allows frequencies below a certain cut-off to pass through?

A low-pass filter is designed specifically to allow frequencies below a certain cut-off frequency to pass through while attenuating the higher frequencies. The fundamental purpose of this type of filter is to block signals with frequencies higher than the designated cut-off, making it ideal for applications where lower frequency components are desired, such as in audio processing or signal conditioning.

In practice, this means that any signal with a frequency lower than the cut-off can exist in its entirety in the output, while those with frequencies above the cut-off are progressively attenuated as their frequency increases. This property is particularly useful in various applications, including removing high-frequency noise from signals or in the design of audio crossover networks.

The other options relate to different filtering functionalities. For instance, a high-pass filter allows frequencies above a certain cut-off to pass while attenuating lower frequencies. A band-stop filter rejects a specific range of frequencies while allowing frequencies outside this band to pass. A notch filter is a more specialized type of band-stop filter that targets a very narrow range of frequencies for attenuation.