To feel a ghost’s presence:
Around 17 Hz: Some studies suggest that frequencies near 17 Hz can create unsettling sensations, possibly linked to resonance with the human body
https://www.instructables.com/Build-an-Infrasonic-Subwoofer/
Ready made speaker/amplifiers:
Rockville RBG12S
Mackie SRM350v3
JBL 308P MkII