Sound
What you enter stays on your device while you use this tool. Opening a shared link sends the settings in its address to HowToolbox to prepare the page.
Sound starts only when you press Play.
Pitch and playback
⚠ Protect your hearing: turn your device volume down before you press Play, especially with headphones, and raise it slowly. The tool keeps its output well below full scale, but how loud it sounds depends on your device. Square and sawtooth waves sound louder than a sine wave at the same setting.
If Play is disabled, this browser can't play sound. The values still work.
Frequency
440 Hz
Nearest note A4, 0 cents · one cycle lasts 2.273 ms
Frequency details
- Wavelength in air at 20 °C
- 78 cm
- Exact frequency of the note
- 440 Hz
- MIDI note number
- 69
- One octave down
- 220 Hz
- One octave up
- 880 Hz
What this means
- An octave up doubles the frequency; an octave down halves it.
- A sine wave is one pure frequency, with no harmonics.
- This is within the range of human hearing, about 20 Hz to 20 kHz.
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Play a test tone from 1 Hz to 20 kHz and see its note, period and wavelength.
How to use
- Choose a waveform and set the frequency, or pick a musical note.
- Press Play and raise the volume slowly.
- Press Stop when you're done.
Note frequencies from middle C
| Note | Frequency |
|---|---|
| C4 | 261.63 Hz |
| C♯4 | 277.18 Hz |
| D4 | 293.66 Hz |
| D♯4 | 311.13 Hz |
| E4 | 329.63 Hz |
| F4 | 349.23 Hz |
| F♯4 | 369.99 Hz |
| G4 | 392 Hz |
| G♯4 | 415.3 Hz |
| A4 | 440 Hz |
| A♯4 | 466.16 Hz |
| B4 | 493.88 Hz |
Equal temperament with A4 at 440 Hz.
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How it works
Sound is air vibrating. A tone is a vibration that repeats at a steady rate, its frequency f, measured in hertz (Hz): 440 Hz means 440 vibrations every second, and the higher the frequency, the higher the tone. One vibration lasts T = 1 / f, and the wave it makes in the air is λ = c / f long, where c is the speed of sound (343 m/s at 20 °C): at 440 Hz, 2.27 ms and 78 cm.
A speaker makes a tone by moving back and forth at that rate. The shape of the movement is the waveform: a sine wave is one pure frequency, while square, triangle and sawtooth waves add quieter tones at whole multiples of it (harmonics), which makes them sound brighter or buzzier.
Musical notes are frequencies too. Each octave doubles the frequency and is divided into 12 equal steps: f = 440 · 2^(n / 12), where n is how many steps the note is above A4 (440 Hz). Middle C is 9 steps below A4, so it is 440 · 2^(−9 / 12) ≈ 261.63 Hz.
Young ears hear about 20 Hz to 20 000 Hz, and the top end drops with age. Small speakers can't play deep bass. Loud tones can damage hearing permanently, so start quiet. Sources: ISO 16 (A4 = 440 Hz), ISO 9613-1 (speed of sound), WHO-ITU H.870 (safe listening).
Frequently asked questions
Why is 440 Hz the standard tuning note?
It was agreed internationally so that instruments everywhere tune to the same pitch; ISO 16 sets A4 at 440 Hz.
I can't hear the high or low tones. Is something wrong?
Probably not. Hearing above about 15 000 Hz fades with age for most adults, and small speakers simply can't play very low tones.
Why does the square wave sound louder than the sine wave?
It carries more energy at the same volume setting, spread over its harmonics, so it sounds louder and harsher.
Is using a tone generator safe?
Yes, at sensible volumes. Pure tones can be piercing, especially in headphones: keep the volume low and sessions short.
How do I test a subwoofer?
Play a sine tone, start quiet and step down from 100 Hz towards 20 Hz. Most subwoofers reach 30–40 Hz; a rattle at one frequency usually comes from the room or the furniture, not the speaker.
What is the mosquito tone?
A tone around 17,000 Hz that many teenagers hear and most adults no longer do. Whether you hear it also depends on your speakers or headphones.
Is this a hearing test?
Only a rough one: it shows which tones you hear on your own speakers at an unknown level. A real hearing test uses calibrated equipment, so see a professional if you notice changes in your hearing.
What is 528 Hz?
A tone a little above C5 (523.25 Hz). Claims that it heals or repairs DNA have no scientific support.
What does the waveform show?
Before Play, it shows a still preview at the selected frequency and volume. While playing, it shows the sound signal; during a sweep, the waves move closer together as pitch rises. With reduced motion, the preview stays still.
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