Tone Generator

About the tone generator

This tool plays a steady tone at the exact frequency you choose, from 20 Hz (a deep rumble) to 20,000 Hz (a very high whistle). Type a number, drag the slider, or pick one of the quick buttons. The tone changes smoothly while it plays, so you can move through the range and listen.

Under the number you see the musical note that the frequency is closest to — for example *A4* for 440 Hz, or *C4 −2 cents* when it is a little flat.

How to use it

• Press Play
• Type a frequency, or drag the slider — it moves in octaves, so low and high notes are equally easy to reach
• Use ÷2 and ×2 to jump an octave down or up, and −1 Hz / +1 Hz for small steps
• Pick a Wave shape: Sine is the pure tone, the others sound brighter
• Open Frequency sweep to glide from one frequency to another over a few seconds

Wave shapes

• Sine — one pure frequency and nothing else. Use it for tests and tuning.
• Square — hollow and buzzy, like an old video game. It has many odd harmonics.
• Triangle — softer than square, between a sine and a flute.
• Sawtooth — bright and sharp, the classic synthesizer sound. It has every harmonic.

All four shapes play at about the same loudness at the same volume setting.

What people use it for

• Checking speakers and headphones — find the lowest bass note your speakers can play, or listen for rattles and buzzes
• Finding a room resonance — sweep slowly through 30–200 Hz and listen for notes that suddenly boom
• Tuning an instrument — 440 Hz is the standard A; play it and tune to it by ear
• Electronics and audio work — a quick test signal for an amplifier, a filter or a sound card
• Science lessons — show how pitch rises with frequency, or how two tones beat together
• Subwoofer setup — play 30, 40, 50 Hz and set the level

Frequency sweep

A sweep glides from one frequency to another. It moves by octaves, so 20→40 Hz takes as long as 10,000→20,000 Hz — that is how the ear hears pitch. A slow sweep through the bass is the easiest way to hear where speakers stop, or where a room booms.

Frequently asked questions

Is this a hearing test?

No. This tool plays tones for testing equipment, music and teaching. It does not measure hearing. If you are worried about your hearing, talk to a doctor or an audiologist.

Why can I not hear the very low or very high tones?

Small speakers, like the ones in a phone or a laptop, cannot play deep bass — often nothing below 100–200 Hz. Very high tones are hard to hear too, and that gets more common with age. Try good headphones, but keep the volume low.

Is the frequency exact?

The browser makes the tone with its own audio engine, so it is very close to the number you see. Your sound card and speakers can add a little distortion, especially at high volume.

Does it work on a phone?

Yes, in any modern browser. On an iPhone, turn off silent mode, or the tone may not play.

Does the tone stop when I leave the page?

Yes. Closing the tab stops it. Press Stop before you switch tabs if you do not want it playing in the background.

Good to know

• Your frequency, wave shape and volume are remembered in this browser for next time
• Press Enter in the number box to play, and use the ↑ ↓ arrow keys for 1 Hz steps (hold Shift for 10 Hz)
• Nothing is recorded or sent anywhere — the sound is made in your browser

Related tools

• Left Right Speaker Test — check that left and right are the right way round
• Guitar Tuner — tune with your microphone
• Metronome — a steady click at any tempo
• White Noise — calm background sound
• Microphone Test — check your microphone