How tone generator works
Enter a frequency in hertz or pick a note and octave, choose a waveform, and press Play — the tone sounds immediately through your browser's Web Audio oscillator, with no audio files and no server. Any frequency from 20 Hz (the bottom of human hearing) to 20 kHz (roughly the top for young ears) works; a note input is also provided, so A4 plays 440 Hz and C4 plays 261.63 Hz under the standard equal-tempered scale.
Four waveforms are available. Sine is a pure single frequency with no overtones — the cleanest choice for hearing tests and speaker checks. Square contains odd-numbered harmonics and sounds hollow, like a chiptune. Sawtooth contains all harmonics and is the classic bright synth lead. Triangle sits between sine and square, with a soft, flute-like edge. When you type a frequency instead of a note, the tool reports the nearest musical note and how many cents away it is.
Everything is computed and played locally: the page asks your browser for an audio channel the moment you press Play (browsers require a click before sound can start), shapes the volume with a short fade to avoid clicks and pops, and keeps going until you press Stop. Lower the volume before playing high frequencies — small speakers distort, and 16 kHz+ is inaudible to many adults anyway.