Online Tone Generator (Frequency Generator)

A tone generator that plays any frequency from 1 Hz to 22,000 Hz in steps of 0.01 Hz. The slider is logarithmic, so the low and high ends get the same room, the octave buttons halve or double the frequency, and ±1 moves it by one hertz. Presets cover 50 and 60 Hz mains hum, middle C (261.63 Hz), A4 (440 Hz), 1 kHz, 10 kHz and 15 kHz.

There are four waveforms. A sine wave is a pure tone with no harmonics; square, sawtooth and triangle waves carry harmonics, so the same frequency sounds brighter. Setting the channel to left or right plays only through that speaker or earbud, which checks that a pair is wired the right way round. Changes while playing glide instead of jumping, so there is no click. The nearest note and its offset in cents are shown too (A4 = 440 Hz).

The tone can also be saved as a WAV file of 1 to 30 seconds (44.1 kHz, 16-bit stereo), rendered by the same audio graph, with a 10 ms fade at each end so it starts and stops cleanly.

Loud high tones can damage hearing, so start low; the default volume is 20%. What you actually hear depends on your speakers and your age: most adults cannot hear near 20 kHz, and small speakers produce little below 100 Hz. That is why this cannot measure hearing or a speaker's frequency response with any accuracy.