Rolloff Slope

Typically, a filter’s rolloff is measured in decibels-per-octave. Thus a shallow slope, such as 6dB per octave, would allow some frequencies beyond the cutoff frequency to be heard, but at a reduced amplitude. Steep rolloff slops, such as 24dB per octave, result in frequency components close to the cutoff frequency to be reduced in amplitude so much that they are generally below the threshold of audibility. As you’d expect, a 12dB rolloff slope falls somewhere between these two extremes.