About the 20 Hz tone
20 Hz is usually given as the lowest frequency humans can hear, and at this level it's felt as much as heard. Most laptop and phone speakers can't reproduce it at all; you'll need good headphones or a subwoofer. Keep the volume low: at very low frequencies it's easy to push speakers too hard.
A 20 Hz sine wave completes 20 cycles every second; each cycle lasts 50.000 ms, and the sound wave is about 1715.0 cm long in air. The nearest musical note is D♯0.
Start with the volume low and raise it slowly. Use the slider to move away from 20 Hz, or try another preset: 40 Hz · 50 Hz · 60 Hz · 100 Hz · 256 Hz · 432 Hz · 440 Hz · 528 Hz · 1,000 Hz · 8,000 Hz · 15,000 Hz · 17,400 Hz · 20,000 Hz.
Questions
How do I play a 20 Hz tone?
Press Play above. The generator starts at exactly 20 Hz as a pure sine wave; you can change the wave shape and volume.
Why can't I hear 20 Hz?
Your speakers or headphones may not reproduce it, the volume may be too low, or it may be outside your hearing range. Very low and very high tones are the hardest.
Is it safe to listen to test tones?
At a comfortable volume, yes. Start quiet, and stop if anything feels uncomfortable.
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