What this tone generator can do
A tone generator makes a steady sound at a frequency you choose. Frequency is measured in hertz (Hz), the number of vibrations per second. Low numbers sound deep, high numbers sound thin and bright. Most adults hear from about 20 Hz to somewhere between 12 and 17 kHz, and the range shrinks with age.
Everything on the page is made by your browser's audio engine. There is no file to download and no recording from the microphone.
- Frequency control. A logarithmic slider from 20 Hz to 20 kHz, plus a box where you can type any value, including decimals such as 432.5.
- Fine steps. Buttons for plus and minus 1 Hz, and for halving or doubling the frequency to jump one octave.
- Note display. The nearest musical note and how many cents sharp or flat you are from it.
- Waveforms. Sine, square, triangle and sawtooth.
- Output channel. Left, both or right, to test one speaker at a time.
- Volume and a live oscilloscope that draws the wave as it plays.
- A sweep that glides from one frequency to another over the time you set, with an exponential option.
- Presets for 50 Hz hum, 60 Hz hum, 100 Hz, A4 440, 1 kHz, 10 kHz and 15 kHz.
Why a log slider? Musical pitch is logarithmic. Going from 100 Hz to 200 Hz sounds the same size of step as going from 1,000 Hz to 2,000 Hz. A linear slider would squeeze everything below 1 kHz into a tiny strip. A log slider gives each octave the same room.
Presets and what they are for
The preset buttons save you typing the numbers people use most. Each one has a practical use.
| Preset | Frequency | What it is useful for |
|---|---|---|
| 50 Hz hum | 50 Hz | Matches mains hum in Europe, Asia and most of Africa. Helps you spot a ground loop or a noisy cable |
| 60 Hz hum | 60 Hz | Matches mains hum in North America. Same use, other power grid |
| 100 Hz | 100 Hz | Deep bass. A quick check that a small speaker can reproduce low notes |
| A4 440 | 440 Hz | The standard tuning note. Use it to tune an instrument by ear |
| 1 kHz | 1000 Hz | The usual reference tone for levels and for checking the mid range |
| 10 kHz | 10,000 Hz | A high treble tone. Tests tweeters and the top of your hearing |
| 15 kHz | 15,000 Hz | Very high. Many adults over 40 cannot hear it, and some speakers cannot play it |
Mains hum is worth knowing. The grid runs at 50 or 60 Hz, and electrical interference leaks into audio at that frequency, plus multiples at 100 and 120 Hz. Playing the tone beside your recording lets you match the hum by ear and then find the right place for a notch filter.
Notes and frequencies
Western music uses equal temperament. Each semitone is the twelfth root of two (about 1.0595) times the one before it, and each octave doubles the frequency. The reference is A4 at 440 Hz. Here is the octave around middle C.
| Note | Frequency (Hz) |
|---|---|
| C4 (middle C) | 261.63 |
| D4 | 293.66 |
| E4 | 329.63 |
| F4 | 349.23 |
| G4 | 392.00 |
| A4 | 440.00 |
| B4 | 493.88 |
| C5 | 523.25 |
The A in every octave has a neat value, because each octave doubles the one below. Use the octave buttons to jump between them.
| Octave | A frequency (Hz) |
|---|---|
| A1 | 55 |
| A2 | 110 |
| A3 | 220 |
| A4 | 440 |
| A5 | 880 |
| A6 | 1760 |
| A7 | 3520 |
| A8 | 7040 |
A cent is one hundredth of a semitone. The display shows how far the current frequency sits from the nearest note, so you can see that 442 Hz is about 8 cents sharp of A4. Under 5 cents, most listeners cannot tell the difference from the exact note.
Sine, square, triangle and sawtooth
A waveform is the shape of one vibration. The shape decides which extra frequencies, called harmonics, ride along with the main one. Harmonics are what give a sound its colour. Watch the oscilloscope as you change the shape.
| Waveform | Harmonics | How it sounds | Typical use |
|---|---|---|---|
| Sine | None, only the fundamental | Pure, smooth, a little dull | Hearing tests, speaker checks, finding resonances |
| Triangle | Odd harmonics, weak (falling as 1 over n squared) | Soft and hollow, a bit like a flute | Gentle tones when a sine is too plain |
| Square | Odd harmonics (falling as 1 over n) | Buzzy, hollow, reedy | Testing distortion, retro game sounds |
| Sawtooth | All harmonics (falling as 1 over n) | Bright, harsh, rich | Brass-like tones, checking filters and tweeters |
For measurement, stick to sine. A square or sawtooth wave contains energy at many frequencies, so a speaker that cannot play 15 kHz may still seem to play a 5 kHz sawtooth, because its harmonics land at 10 kHz and below. If you want to know whether a driver reaches a frequency, a sine tells the truth.
Frequency sweep
A sweep glides from a start frequency to an end frequency. Set the start, the end and the number of seconds, and choose exponential or linear motion. Exponential spends the same time on every octave, which matches how we hear pitch. Linear spends most of its time in the highest frequencies.
Numbers show the difference. The range 20 Hz to 20 kHz is almost ten octaves (about 9.97). In a 20-second exponential sweep each octave takes roughly two seconds. In a linear sweep of the same length, half the time, ten seconds, is spent above 10 kHz, which is only the last octave.
| Sweep setting | From | To | Suggested length |
|---|---|---|---|
| Full range | 20 Hz | 20 kHz | 20 to 30 seconds |
| Bass only | 20 Hz | 200 Hz | 10 to 15 seconds |
| Mid range | 200 Hz | 2 kHz | 10 seconds |
| Treble and hearing top end | 8 kHz | 20 kHz | 15 to 25 seconds |
Sweeps are the quickest way to find trouble. Listen for rattles in a case, a buzzing panel, or a sudden jump in loudness. These show up as a spot where the sound changes character. Stop the sweep there and type that frequency in to examine it.
Common ways to use a tone generator
- Tuning. Play A4 440 and match your string, reed or voice to it. For other notes, use the table above.
- Speaker and subwoofer testing. Step through 100, 60, 40 and 30 Hz at low volume. A sub that disappears below 40 Hz is rolling off. Send the tone to Left, then Right, to check each side.
- Room resonances. Some bass notes boom in a room because of standing waves. Sweep slowly through 30 to 120 Hz and listen for notes that sound much louder.
- Tinnitus matching. Some people use a tone generator to find the pitch of the ringing they hear. This can help describe it to a clinician. It is not medical advice or a diagnosis, and a hearing professional should check any ringing that persists.
- Science classes. Show how pitch changes with frequency, how waveforms differ, or how interference works using the left and right outputs.
- A quick hearing check. Play 8, 10, 12, 15 and 17 kHz at low volume to see where you stop hearing.
You can also split a song into its parts at /vocal-remover/ and find a song's tempo and key at /bpm-finder/. The key result tells you which note to tune to, and the generator then plays it.
Room modes and wavelengths
Low sounds are long. The wavelength is the speed of sound, about 343 metres per second at 20 degrees Celsius, divided by the frequency. A 50 Hz wave is nearly 7 metres long, which is why bass reacts so strongly to room size.
| Frequency | Wavelength (approx.) |
|---|---|
| 20 Hz | 17.15 m |
| 50 Hz | 6.86 m |
| 100 Hz | 3.43 m |
| 1 kHz | 34.3 cm |
| 10 kHz | 3.43 cm |
| 20 kHz | 1.7 cm |
Between two parallel walls, the lowest standing wave has a half wavelength equal to the distance. The first mode is the speed of sound divided by twice the length. The figures below follow from that.
| Room length | First mode (Hz) |
|---|---|
| 3 m | 57.2 |
| 4 m | 42.9 |
| 5 m | 34.3 |
| 6 m | 28.6 |
Sweep through those frequencies in your own room and you may hear a strong boom at a number close to the table value. It will change if you move your listening position, which is a sign of a room mode and not of the speaker.
Safety: start quiet
A steady tone is tiring and can be loud. A generator has no limiter, so volume is your job.
- Turn the volume down before you press play, and raise it slowly.
- Take headphones off or hold earbuds away from your ears while you set a new frequency.
- Be careful with high frequencies. Tweeters are small and can burn out if you play a loud 10 kHz or 15 kHz tone for a long time.
- Keep square and sawtooth waves quiet. They carry more energy than a sine at the same setting.
- Do not play very high tones near pets. Dogs and cats hear far above 20 kHz.
- Stop if you feel pain, ringing or discomfort.
These tones are for testing and learning. They are not a treatment and not a hearing test. If you are worried about your hearing, see an audiologist.
Frequently asked questions
Is this tone generator free?
Yes. It is free, with no sign-up, no download and no time limit. The tones are created by your browser, so nothing is sent to a server and the page does not need a microphone. It works on desktop, tablet and phone browsers.
What frequency range does it cover?
It covers 20 Hz to 20 kHz, the usual range of human hearing. You can type any value in that range, including decimals, or use the log slider. Whether you hear the whole range depends on your ears and on your speakers or headphones.
Which waveform should I choose?
Use sine for tuning and for testing speakers or hearing, because it has only one frequency. Pick square, triangle or sawtooth if you want to hear harmonics or to test how a filter or amplifier handles a richer signal.
Why can't I hear very low or very high tones?
Small speakers and laptops cannot move enough air to play below about 100 Hz, and most adults lose the top of their hearing with age. If a tone is silent, try headphones, or check that the volume is up. A sound you cannot hear may still be playing.
What does cents mean in the note display?
A cent is one hundredth of a semitone. The display names the nearest note and shows how many cents your frequency is above or below it. Zero means exactly in tune with A at 440 Hz. A few cents either way is hard to hear.
What is the difference between exponential and linear sweep?
An exponential sweep covers each octave in the same time, which sounds even to the ear. A linear sweep moves by the same number of hertz each second, so it races through the low notes and crawls through the highs. Exponential is better for most tests.
Can I use it to test a subwoofer?
Yes, at low volume. Play 100, 60, 40 and 30 Hz one at a time, or run a bass sweep from 20 to 200 Hz. A sub that fades away below 40 Hz is rolling off. Start quiet, because low tones can rattle things before they sound loud.
Can it help with tinnitus?
Some people use a tone to match the pitch of their ringing, which can help when describing it. This is not medical advice, and the tool does not diagnose or treat anything. Keep the volume low and see a hearing professional if ringing continues.
Is it safe for my speakers and ears?
It is safe when you start quiet and raise the volume slowly. Loud continuous high tones can overheat a tweeter, and any loud sound can harm hearing. Keep headphones off your ears while setting a new frequency, and stop if anything hurts.