440 Hz Tone – A4 Tuning Note

What is 440 Hz?

440 Hz is the note A above middle C (written A4). It is the standard tuning pitch used by most orchestras, bands, instrument makers and tuning apps around the world. When musicians "tune to A", they usually mean this exact frequency: the air vibrates 440 times per second.

This page plays a clean 440 Hz tone so you can tune an instrument by ear, check a tuning fork, test speakers or headphones, or use it as a reference pitch for singing.

How to tune an instrument to 440 Hz

1. Press Play 440 Hz and set a comfortable volume.
2. Play the A string (guitar 5th string at the 5th fret, violin A string, piano A4) or sing an "ah".
3. Listen for beats – a slow "wah-wah" wobble. The slower the beats, the closer you are.
4. Adjust until the wobble disappears. Then you are in tune with A4 = 440 Hz.

The triangle option is softer and easier to listen to for a long time; the square option has strong harmonics, which can make beats easier to hear with bright instruments.

Why 440 Hz is the standard

Before the 20th century, orchestras tuned to many different pitches, roughly from 415 to 450 Hz. To make it easier for musicians and instrument makers to work together, an international conference in London in 1939 recommended A = 440 Hz, and the International Organization for Standardization later adopted it as the standard tuning frequency (ISO 16). Some orchestras still tune slightly higher, such as 442 or 443 Hz, for a brighter sound.

440 Hz vs 432 Hz

432 Hz is about 32 cents (roughly a third of a semitone) lower than 440 Hz. Some musicians prefer it and describe it as warmer. Claims that 432 Hz is "natural" or has special healing powers are not supported by scientific evidence – both are simply reference pitches. Hear the difference with our 432 Hz tone.

Notes near 440 Hz

Need another note? Type the frequency into our tone generator.

Using 440 Hz to test audio equipment

A 440 Hz tone sits in the middle of the audible range, so almost every speaker, phone and earbud can play it clearly. It is useful for checking that both channels work (switch between speakers with the left right audio test), for listening for distortion and buzzing, and as a calibration tone. For bass and treble checks use the speaker test.

Supported devices and browsers

• Any devicePhones, tablets and computers with Chrome, Edge, Firefox or Safari.
• OutputSpeakers, headphones or Bluetooth. The tone is generated live, so it never loops or clicks.

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