What a tone generator is useful for
A tone generator produces a signal of one known frequency, which makes it a surprisingly versatile diagnostic tool. The 440 Hz preset is concert pitch A4 for tuning instruments. A 1 kHz sine is the standard reference for setting levels on mixers and interfaces. A 10 kHz tone quickly reveals whether a tweeter is alive, and 60 Hz (or 50 Hz in much of the world) lets you compare a suspected ground-loop hum against the real thing. Sweeping the slider slowly through a room can even expose rattles and resonances in furniture and speaker cabinets.
How the generator works
The tone comes from a Web Audio oscillator running in your browser — no audio files, no server. Frequency, waveform and volume all update live while the tone plays, so you can sweep smoothly instead of stopping and restarting. One small quality touch: the gain ramps up and down over about 15 milliseconds on start and stop. Starting a waveform mid-cycle at full volume produces a sharp click; the short ramp removes it, which matters when you are listening for artifacts rather than creating them.
The frequency slider is logarithmic, matching how hearing works: the octave from 100 to 200 Hz gets as much slider travel as the octave from 5 to 10 kHz, so low frequencies are not squashed into the first few pixels.
A note on hearing safety
Pure tones concentrate all their energy at one frequency, and the ear judges loudness poorly above 8 kHz or so — a high tone can be doing damage before it feels loud. Begin every test at low volume and raise it gradually. If you need steady timing rather than steady pitch, the Online Metronome uses the same audio engine to produce sample-accurate clicks.