About the Tone Generator
This Tone Generator plays a steady tone at the frequency you choose, from 20 Hz to 20,000 Hz. Type a frequency, drag the slider, which is spaced by pitch so that each octave takes the same distance, or press a preset such as A4 440 Hz, Middle C, 1 kHz or 60 Hz. The display names the nearest musical note and how many cents you are above it. You can choose a sine, square, triangle or sawtooth wave, set the volume, use a note picker to jump to a note and octave, and set a timer that stops the tone after 10, 30 or 60 seconds. The tone starts only when you press Play, and it changes smoothly while it plays. What you hear depends on your speakers or headphones. It is not a calibrated test signal and must not be used for medical hearing tests. Loud tones can damage hearing and equipment.
Updated September 2026
How to use the Tone Generator
- 1Type a frequency, use the slider, or press a preset. The note name appears under the number.
- 2Choose a waveform: sine, square, triangle or sawtooth.
- 3Turn the volume down low, then press Play.
- 4Change the frequency, waveform or volume while it plays, and press Stop when you finish.
Playing a pure tone
Type a number between 20 and 20,000 in the Frequency box, or drag the slider. The slider uses a logarithmic scale, so moving it equal distances changes the pitch by equal musical steps, and it is easy to reach 440 Hz as well as 8 kHz. The buttons under it nudge the frequency by 1 or 10 Hz for fine tuning.
Press Play to start. Browsers only allow sound after a click, so the tone never starts by itself. Changing the frequency, waveform or volume while it plays is smooth, and starting and stopping fade over a fraction of a second so that you do not hear clicks.
Waveforms and how they sound
The shape of the wave decides its sound. A sine wave is the simplest and is heard as a smooth, pure note. A triangle wave adds faint odd overtones. A square wave has strong odd overtones and sounds hollow, like an old video game. A sawtooth wave has all the overtones and sounds bright and buzzy. At very high frequencies the computer-made shapes are less clean, and the difference between them is harder to hear.
Notes and frequencies
The readout under the number shows the closest note in equal temperament, using sharps, and the number of cents above or below it. A cent is one hundredth of a semitone. Use the Note and Octave lists and press Set to jump to a note, for example A4 or C5. This is useful for tuning a guitar string or a piano key by ear.
The presets include 60 Hz, the mains hum in many countries, which is handy for checking whether a speaker or an amplifier picks up interference. Tones are a good starting point for audio checks. Capture what you hear with the Voice Recorder, make sentences audible with Text to Speech, record the screen while you test with the Screen Recorder, and use the Morse Code Translator to turn a message into beeps.
Safe listening and testing speakers
- Start with the volume low and raise it gradually.
- Take headphones off before you change to a very different frequency.
- Do not play loud tones at the extremes of the range through small speakers.
- Use the timer for long tests so that the tone stops by itself.
- This tool is not a calibrated hearing test or a measuring instrument.
Features
- Any frequency from 20 Hz to 20,000 Hz
- Sine, square, triangle and sawtooth waveforms
- Note name and cents readout
- Logarithmic slider plus buttons for -10, -1, +1 and +10 Hz
- Note and octave picker
- Presets: 440 Hz, Middle C, 1 kHz, 100 Hz, 60 Hz and 10 kHz
- Volume control and an optional 10, 30 or 60 second timer
- Smooth changes with no clicks
Frequently asked questions
What is a tone generator used for?
People use one to tune instruments, test speakers and headphones, check how low or high a device can play, find a rattle in a room, or learn how pitch works. It plays one clean tone, unlike a music player.
What is the frequency of A4?
A4, the A above middle C, is 440 Hz in standard tuning. Middle C is about 261.63 Hz. The tool uses equal temperament, where each semitone is a factor of the twelfth root of two, and the display shows the nearest note.
What is the difference between sine, square, triangle and sawtooth waves?
A sine wave is the purest sound with a single frequency. Square waves sound hollow and buzzy, triangle waves are softer than square, and sawtooth waves sound bright and harsh. The last three contain extra overtones, which is why they sound richer than a sine at the same pitch.
Can I use it to test speakers?
You can use it for a rough check: play a low tone to hear whether the bass speaker moves, then sweep upward to find any rattles or gaps. It is not a calibrated signal, so it cannot measure how accurately a speaker performs.
Why can't I hear very high or low tones?
Small speakers cannot move enough air to play tones below about 100 Hz, so you may feel or see nothing. Many people cannot hear above 15 to 17 kHz, and the upper limit falls with age. If you hear nothing, it does not mean the tone is not playing.
Is it safe to play loud tones?
Keep the volume low, especially with headphones, and raise it slowly. Loud steady tones can damage hearing and can also overheat or damage speakers, most of all at very high or very low frequencies. Stop if anything sounds distorted or uncomfortable.