Tone & Frequency Generator

This tone generator synthesises a pure tone anywhere from 20 Hz to 20 kHz — the full span of healthy human hearing — straight from a Web Audio oscillator in your browser, with nothing to install. Frequency is pitch: 440 Hz is the A above middle C (concert-pitch "A4"), so the readout also shows the nearest musical note and how many cents sharp or flat you are, which makes it a quick tuning reference.

The waveform choice changes the timbre because of harmonic content. A sine wave is the pure fundamental with no overtones; a triangle adds faint odd harmonics; square and sawtooth waves are harmonically rich and sound buzzy or bright. That matters when you are testing gear: a sine is best for measuring a single frequency cleanly, while richer waves reveal how a speaker handles harmonics. You can route the tone to the left ear, right ear or both to check each channel independently.

Two built-in tests use the acoustics directly. The frequency sweep glides smoothly from a low to a high frequency (log or linear) and loops, which surfaces speaker rattles, room resonances and dead spots. The hearing-range test steps up through the highest frequencies and asks what you can still hear — most people lose the top end with age (presbycusis), so the highest tone you catch gives a rough hearing-age estimate. Start the volume low: high frequencies at full volume can harm both ears and speakers.