How to play a tone
- Drag the slider to pick a frequency, or type an exact value in the box next to Hz. ×2 and ÷2 jump an octave, ±1 st a semitone and ±1 Hz one hertz.
- Choose a wave shape: Sine for a pure tone, or Square, Sawtooth or Triangle for a brighter sound.
- Turn the Volume down, press Play or the space bar and raise it slowly. You can change the frequency, shape, volume and Balance between left and right while it plays.
What people use it for
- A tuning reference. 440 Hz is A4, the pitch most instruments tune to. Play it as a sine wave and tune by ear, or use ÷2 to get A3 at 220 Hz.
- Testing speakers and subwoofers. Slide down slowly from 200 Hz and listen for where the bass fades out, or for rattles and buzzing at particular frequencies.
- Finding the top of your hearing. At a low volume, raise the frequency slowly and note where the tone disappears. The result depends on your headphones as much as your ears, so treat it as a curiosity, not a hearing test.
- Science and music lessons. Press ×2 a few times to show that each octave doubles the frequency, or switch wave shapes to show how the same pitch can sound completely different.
Frequencies worth knowing
| Frequency | What it is |
|---|---|
| 50 Hz or 60 Hz | Mains hum: 50 Hz in Europe and many other regions, 60 Hz in North America |
| 261.63 Hz | Middle C (C4) |
| 440 Hz | A4, the usual tuning pitch |
| 1,000 Hz | The common reference tone for audio testing |
A word of care: tones near the edges of your hearing can seem quiet even when your speakers are working hard. Don’t keep turning the volume up to chase a tone you can’t hear, as that is how hearing and tweeters get damaged. Short listens at a comfortable level are enough for every use above.