Free Online Tone Generator
440 Hz
A4
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About the Tone Generator
Generate a pure tone at any frequency (20 Hz – 20 kHz) with sine, square, sawtooth or triangle waveform — displays the musical note and cents deviation, all in your browser.
How to use the Tone Generator
- 1Click the play button (or press Space) to start the tone.
- 2Drag the frequency slider or type an exact Hz value to change the pitch — the note name and cents offset update in real time.
- 3Choose a waveform: Sine is the purest tone, Square and Sawtooth are buzzy, Triangle is softer.
- 4Adjust the volume slider to a comfortable listening level.
- 5Use the note presets to jump to standard reference frequencies like A4 (440 Hz) or Middle C.
Frequently asked questions
What is this tool used for?
Common uses include hearing tests (checking the range you can detect), tuning instruments by ear, testing speakers and headphones, and calibrating audio equipment. The A4 440 Hz sine tone is the standard reference for tuning.
What do the waveforms sound like?
Sine is a pure, smooth tone with no harmonics. Square has a hollow, buzzy character (think old video-game sounds). Sawtooth is bright and harsh (closest to a bowed string). Triangle is softer than square — similar to a flute or recorder.
What do the cents mean?
One cent is 1/100th of a semitone. The display shows how many cents above (+) or below (−) the nearest standard note your chosen frequency is. A deviation of ±50 cents is half a semitone — more than that and the note sounds out of tune.
Why can't I hear very high frequencies?
Human hearing typically ranges from 20 Hz to 20 kHz, but the upper limit decreases with age — adults commonly top out at 15–16 kHz. If you cannot hear tones above 14 kHz, that is normal. Headphone quality also matters at the extremes.
Is this safe at any volume?
Start with the volume slider low and increase gradually. Sustained loud tones — especially through headphones — can cause ear fatigue or damage. This tool defaults to 60% volume; treat it like any audio source and listen at a comfortable level.