A dB/Octave (dB/Octave) is the unit that measures the slope or "aggressiveness" of a filter's curve.

Think of the slope of a hill. A low dB/octave value represents a gentle slope, while a high value represents a very steep slope.

In the context of a filter (such as a high-pass or low-pass filter), this value indicates how quickly the filter attenuates the sound after the cutoff frequency.

"Octave" here means doubling or halving the frequency.

• 6 dB/Octave: This is a very smooth first-order filter. For each octave beyond the cutoff frequency, the volume is reduced by 6 dB.

• 12 dB/Octave: This is a second-order filter.

• 18 dB/Octave: This is a third-order filter..

• 24 dB/Octave: This is a very steep fourth-order filter with a very abrupt cutoff. It's the most common slope in filters for classic analog synthesizers.