What is 440 Hz?
440 Hz is a tone in the midrange region — the core of speech and most instruments. Its nearest musical note is A4, and its sound wave is roughly 0.78 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.
440 Hz is A4, the international concert-pitch standard (ISO 16) that orchestras and tuners around the world reference. It is the single most useful tuning tone: match your instrument's A string to this and you are in tune with almost everyone else.
What you can use a 440 Hz tone for
- Tuning instruments by ear against a reference A
- Comparing 432 Hz vs 440 Hz tuning
- Checking speaker warmth and 'boominess'
- Room-mode and standing-wave hunting
- Tuning instruments to concert pitch
Can you hear 440 Hz?
This sits in the range where human hearing is most sensitive, so almost everyone hears it clearly at a low volume. 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 440 Hz test tone?
A 440 Hz test tone is a pure sine wave vibrating 440 times per second. It falls in the midrange range (the core of speech and most instruments) and its nearest musical note is A4. You can play it instantly above to test audio equipment or your hearing.
Can everyone hear 440 Hz?
This sits in the range where human hearing is most sensitive, so almost everyone hears it clearly at a low volume.
What note is 440 Hz?
The nearest equal-tempered note to 440 Hz is A4 (essentially exact).
Is it safe to play 440 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.