Here is a simple tutorial on the why and how of using a High Pass Filter in Soundtrack Pro.
Audio filters and audio effects are one of the main aspects of post-production audio software like Apple's Soundtrack Pro. These audio filters are often used to correct common problems that occur when you are recording your audio. The high pass filter is a common type of audio equalizer that is used to remove any low lying tones that are interfering with the sound you want. Just as the name suggests, this audio equalizer essentially lets the high tones pass through while the lower tones are restricted. The high pass filter has always been a standard type of audio equalization and Soundtrack Pro keeps the high pass filter as a standard. Here is a step by step tutorial on how to apply a high pass filter to your audio track in Soundtrack Pro.
Applying the High Pass Filter
Start by first identifying the segment of audio that holds the low interference that you want to remove. Select it and then go up to Process, then Effects and find Single Band EQ.
From the Soundtrack Pro's Single Band EQ select High Pass Filter, which was right above High Shelving EQ and below High Cut. This will bring up the Soundtrack Pro High Pass Filter that will allow you to adjust the parameters of what you are filtering out, just not as much as a different type of pass filter.
You will likely begin by adjusting the frequency for the high pass filter, which will determine exactly what frequencies are caught and what are allowed to pass. You will also adjust order and smoothing, all of which is really relative to how you want the final sound to appear. You can also assign presets to the high pass filter, but these will have to be ones that you set yourself. You may want to create some high pass filter presets for common sounds that you have come in contact with and have been forced to deal with.
Using the High Pass Filter
When applying the high pass filter you are going to want to limit the overall amount of high pass filter that is applied. Only a small amount of frequency restriction is usually all that is needed, and otherwise it can create a very dramatic change in the sound that may limit its audibility. This is going to be especially true for music tracks that often have a high range of frequencies in the track. This is going to be best if there is a single type of noise that is consistent and very low on the frequency spectrum. By eliminating this sound you will not alter the rest of the audio track too much, but no matter how limited the amount of the high pass filter that is applied in Soundtrack Pro you are going to find some type of alteration to the digital audio playback.