High Pass
This filter will allow only frequencies above a certain frequency to pass, thereby removing lower frequency audio. You can use this filter to remove lower-frequency sounds. The frequency control determines the cut-off frequency, or the point at which the curve hits the -6 dB level, and the "Steepness" control determines how many samples the filter uses as input, indirectly affecting how sharp the drop-off is at the cutoff frequency. You can use the graph in this dialog to see how the filter affects different frequencies.
One effect you can get with this filter is making audio sound as if it were being played on a cheap radio with tinny speakers. Another effect is to use this filter and the Low Pass filter to emulate audio coming through a telephone.