The highest exponent in the transfer function of a circuit, which directly correlates to the number of reactive elements (capacitors and inductors) it contains. In filters, a higher order means a steeper roll-off beyond the cutoff frequency, typically adding 20 decibels per decade per order.
A first-order filter won't cut it for this noise, we need at least a third-order Butterworth to get the roll-off we want.
Each increase in order usually requires an additional reactive component in a passive filter, or another RC stage in an active filter.
Related terms
Roll off
To gradually attenuate a signal's amplitude as its frequency moves past a specific cutoff point.
Band-pass
Describing a circuit or filter that allows a specific range of frequencies to pass while blocking those outside the range.
Lowpass
A type of filter that allows low-frequency signals to pass while blocking higher frequencies.