How it works
The generator builds the tone inside your browser with the Web Audio API: one oscillator, a per-waveform level so the four shapes sound about as loud as each other, and a short fade at the start and the end so there is no click. The slider covers 20 Hz to 20 kHz on a logarithmic scale, the field takes an exact number, and both stay in step. Change the frequency, the waveform or the pan while the tone plays and the sound follows at once. Press Stop and the result card records what played and for how long.
The chip on the panel shows the frequency, the nearest note in scientific pitch notation and the deviation from it in cents, one hundredth of a semitone. The trace shows the waveform being sent to the output; it is the generated signal, not a measurement of the room or the speaker. On a desktop browser the tone keeps playing if you switch to another tab, so you can use it as a reference while working elsewhere; phones may pause it when the browser goes to the background. It stops when you close the page.
What the readout means
The result card shows the frequency that was playing when you pressed Stop, the waveform, the side and the time. It is a log of what you played, useful when you are comparing speakers or repeating a test.
- Note name and cents. A4 +0 ¢ is exactly concert pitch. Positive cents mean sharp, negative flat; 50 cents is a quarter tone.
- Sine. Use it for tuning, for finding a resonance in a room or a rattle in a speaker, and for hearing tests by ear.
- Square and sawtooth. Rich in harmonics; use them to hear a speaker's tweeter working at a low fundamental, or as a raw sound source.
- Left, centre, right. Centre plays the same tone on both channels. Left and right isolate one side, which is the quickest way to find a dead channel in a cable or an adapter.
What to use it for
Finding a rattle: set a sine wave, start around 40 Hz and move the slider up slowly. A buzz that appears and disappears at one frequency is a resonance in the cabinet, the desk or something nearby; move objects until it stops. Testing an extension cable or a headphone splitter: pan left, then right, and confirm each side arrives. Checking a subwoofer crossover: sweep from 40 to 120 Hz in steps and listen for the point where the sound moves from the subwoofer to the main speakers. Reference pitch for tuning: type the frequency of the note and play it in the centre.
For an ear check, go up from 8 kHz in steps of 1 kHz at a low, fixed volume and note where the tone disappears. It is a rough indication, not a hearing test: headphones, volume and your own attention all shift the result by a lot. If you notice a real difference between your ears, or a limit far below what people your age usually hear, see an audiologist.
Volume and hearing safety
Start every session with the system volume low and raise it only as far as you need. A continuous pure tone at the same level as music feels louder and tires the ear faster, and a sudden high tone at full volume in headphones is painful. Do not play tones near their upper limit at high volume for long, and take the headphones off before you change the frequency by a large amount. The generator never raises its own level: the loudness you hear is set by your device, and lowering it there is always enough.
Frequently asked questions
What is the difference between the four waveforms?
A sine wave is a single pure frequency with no overtones, the cleanest signal for testing. A square wave adds every odd harmonic and sounds hollow and buzzy, like an old video game. A triangle wave has the same odd harmonics but much weaker, so it sounds soft and flute-like. A sawtooth contains every harmonic and sounds bright and brassy. The trace on the panel shows the shape as it plays.
Why is the slider not linear?
The slider moves in octaves: each equal step multiplies the frequency by the same factor, so 20 to 40 Hz takes as much travel as 10 to 20 kHz. That matches how pitch is heard. A linear slider would squeeze the whole bass and midrange into the first few pixels. Type an exact value in the field when you need one.
How loud is the tone and can it damage my speakers or ears?
The tone plays at about half of full scale for a sine or triangle wave and lower for square and sawtooth, and your system volume sets the rest. Start low: a steady tone is louder to the ear than music at the same level, and high frequencies at high volume are uncomfortable in headphones. Small speakers are not harmed by a tone at normal listening volume; a clipping amplifier at full volume can harm any speaker, tone or not.
Can I use it to tune an instrument?
Yes, as a reference pitch. A4 is 440 Hz; the chip on the panel names the note nearest to the frequency you set and the deviation in cents, so 432 Hz shows as A4 minus 32 cents. Type the frequency of the note you need, play it and tune by ear. The generator does not listen, so it cannot tell you whether the instrument is in tune; a tuner app does that.
Why does a very high or very low frequency seem silent?
Below about 40 Hz most speakers produce almost nothing and phone speakers stop well above that; above 16 kHz most adults hear nothing even when the tweeter is working. The generator plays the full 20 Hz to 20 kHz regardless. To hear what your speakers or headphones actually reach, run the sweep in the speaker or headphone test and watch the frequency readout.