Audacity will generate tones. Then export them as waves at cd quality. then burn them to an audio disk.

18 hz sounded like a line of dominos falling down, slightly sped up. this in on my 10 yr old altec lansing computer speakers.

audacity is good open source software.

Randy

Axiom M80, Ep600, Qs8, VP150, Crown XLI 2500 , DBX Driverack PA2, Focusrite Scarlet 2i4