What is 20 Hz?
20 Hz is a tone in the sub-bass region — the deepest bass, felt as much as heard. Its nearest musical note is D#0 (about +49 cents away), and its sound wave is roughly 17.15 m long in air. Because it is a pure sine wave, it contains only this one frequency with no harmonics, which is exactly what you want for testing and calibration.
20 Hz sits right at the lower edge of the audible range. Most people feel it in the chest and gut more than they 'hear' it as a pitch, and many speakers, earbuds and laptop drivers cannot reproduce it at all — if you hear nothing, that is usually your hardware, not your ears. It is a favourite tone for checking whether a subwoofer truly extends to the bottom octave.
What you can use a 20 Hz tone for
- Testing subwoofer and speaker bass extension
- Finding room resonances and rattles
- Setting a subwoofer crossover and level
Can you hear 20 Hz?
Most people feel this more than they hear it as a pitch, and many speakers and earbuds cannot reproduce it — if you hear nothing, it is usually your hardware, not your ears. If you are testing your hearing, do it at a modest, consistent volume in a quiet room and compare both ears. For a full walkthrough, see our at-home hearing range test guide. Remember this is a self-check, not a medical diagnosis.
Frequently asked questions
What is a 20 Hz test tone?
A 20 Hz test tone is a pure sine wave vibrating 20 times per second. It falls in the sub-bass range (the deepest bass, felt as much as heard) and its nearest musical note is D#0. You can play it instantly above to test audio equipment or your hearing.
Can everyone hear 20 Hz?
Most people feel this more than they hear it as a pitch, and many speakers and earbuds cannot reproduce it — if you hear nothing, it is usually your hardware, not your ears.
What note is 20 Hz?
The nearest equal-tempered note to 20 Hz is D#0 (about +49 cents away).
Is it safe to play 20 Hz?
Yes, at a sensible volume. Start low and raise it gradually. Very loud tones of any frequency can harm hearing or, at very low frequencies, over-drive speakers — so keep levels comfortable and take breaks.
Explore more test tones
Need a different pitch? Browse every test-tone frequency, or jump to a nearby one:
You can also use the full test tone generator for frequency sweeps, speaker balance and polarity checks, and the tinnitus matcher.