its for a turntable-to eliminate low frequency rumble.
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Only the subsonic filter is for low frequency turntable noise & feedback. The ultrasonic filter is for high frequency interference above the normal range of human hearing. Some amps are sensitive and can oscillate if the signal includes very high frequency info. This can damage the amp or speakers and intermodulate with audible frequencies.
Best approach is to try them on & off and just see if you have a preference. If you don't, just leave them off.
Back in the day many FM sources transmitted a second carrier with commercial "Elevator Music". This sub carrier transmission could often be heard as a high frequency "twittering" when the receiver was set to stereo. It was more pronounced with receivers deploying slope detection than with true FM discriminators.
Anyway it was not uncommon to have a high cut on pre's to make that sub carrier less irritating.