Pure low end on demand: sine tones from 10 to 250 Hz with presets at the frequencies that matter - subwoofer checks, room boom hunting, and bass reference notes. Use headphones or real speakers; laptops cannot reproduce most of this range.
Careful with the volume: low frequencies at high level stress drivers hard - and rattles you hear may be your room, not the speaker.
Below roughly 30 Hz you feel more than hear - a clean system produces pressure without buzz. Tones that boom at one frequency and vanish at another are your room speaking, not the speaker: predict those spots with the room mode calculator. For the guided bass workup use the subwoofer test, and for full-range work the main tone generator covers 20 Hz to 20 kHz.
Testing the bottom octaves: how low a subwoofer or speaker genuinely reaches, where a room booms or cancels, whether cabinets and furniture rattle, and providing reference pitches for bass instruments (low E on a bass guitar is 41.2 Hz).
Three possibilities in order: your playback hardware cannot reproduce it (laptop speakers stop around 200-300 Hz, small earbuds around 40-60 Hz), the volume is below your hearing threshold (sensitivity drops steeply at the extremes), or the tone is playing as feelable pressure rather than audible pitch - 20 Hz sits at the official edge of hearing.
Sweep the 20-80 Hz range rather than trusting one tone: 40-60 Hz shows the power region of the sub, 25-30 Hz separates real subwoofers from pretenders, and 80 Hz checks the crossover handoff to your main speakers.
At sensible volumes, no. At high volume, low frequencies stress equipment (port chuffing, driver bottoming) before they harm hearing - but sustained loud exposure at any frequency damages hearing, so keep sessions moderate.