Which filter type is designed to reject frequencies within a certain range?

The band-stop filter, also known as a notch filter, is specifically designed to reject frequencies within a certain range while allowing both higher and lower frequencies to pass through. This type of filter is particularly useful in applications where it is essential to eliminate unwanted signals that exist within a specific frequency band, such as in audio processing to remove hum or in communication systems to avoid interference from narrowband signals.

In contrast, the other filter types serve different purposes. A low-pass filter allows signals with frequencies below a certain cutoff frequency to pass while attenuating signals with frequencies above that cutoff. A band-pass filter permits signals within a certain frequency range to pass but attenuates frequencies outside this range. An active filter refers to a filter type that uses active components like operational amplifiers along with passive components to achieve filtering but does not inherently describe the function of rejecting a specific frequency range.

Therefore, the band-stop filter is the correct choice as it is explicitly designed to block or attenuate a specific range of frequencies, making it the ideal answer for the question posed.