Noise-Reduction Frequency Range
Noise-reduction frequency range is the band over which a power filter is specified to attenuate unwanted electrical noise.
It describes frequencies in the supply noise, not the audible frequency response of the connected audio system. The amount of attenuation can vary across the band.
Noise-Reduction Frequency Range — Power Filter
For a power filter, the range identifies where its filtering action is characterized. A broad frequency span does not mean equal suppression at every point or address every path by which interference can enter a system.
Compare the range together with attenuation values and test conditions, including the stated noise mode where available. A range alone does not show how much noise is removed. Keep filtering separate from surge protection and voltage regulation; those functions address different electrical conditions.