About the 440 Hz tone
440 Hz is A4, the international standard tuning note that almost all modern music is tuned to. Orchestras tune to it (or a slightly higher 442 Hz), and it's the A that most tuners use as their reference.
A 440 Hz sine wave completes 440 cycles every second; each cycle lasts 2.273 ms, and the sound wave is about 78.0 cm long in air. The nearest musical note is A4.
Start with the volume low and raise it slowly. Use the slider to move away from 440 Hz, or try another preset: 20 Hz · 40 Hz · 50 Hz · 60 Hz · 100 Hz · 256 Hz · 432 Hz · 528 Hz · 1,000 Hz · 8,000 Hz · 15,000 Hz · 17,400 Hz · 20,000 Hz.
Questions
How do I play a 440 Hz tone?
Press Play above. The generator starts at exactly 440 Hz as a pure sine wave; you can change the wave shape and volume.
Why can't I hear 440 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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