OP wants HZ but gets SPL (“I didn’t order umm”) suggestions as though he were the brain dead one. LOL.
OP, there are free versions of tone generators, SPL meters and spectrum analyzers available in the Apple App Store or Google Apps. HSU Research has a test tone CD that has the absolute cleanest 16HZ recordings on the planet, should you be interested in the extreme. I’ve gotten one free with every sub. Probably available for sale on the cheap. It has a bunch of other test pieces as well including music and pink/white noises. In the event you’re looking at 20HZ and up, the free stuff will do nicely.
(Mr. Anderson was here.)