Tone Generator

How to use the tone generator

1. Lower the Volume first. The slider starts at 20 %, which is a comfortable level on most devices. Put your headphones on only after you have heard the tone through them at a low level.
2. Type a value in Frequency (Hz), drag the logarithmic slider below it, or choose a note in Note. Every value from 20 Hz to 20,000 Hz is accepted, including decimals such as 432.5 Hz.
3. Choose a Waveform: Sine, Square, Sawtooth or Triangle.
4. Press Play. The button turns into Stop. While the tone plays you can change the frequency, the waveform and the volume, and the sound follows immediately.
5. Use Octave down (÷2), Octave up (×2), −1 Hz and +1 Hz for quick, precise steps.

Below the controls, this tool shows the Nearest note (with its deviation in cents), the Period of one cycle and the Wavelength in air. The sound is synthesized live by your browser with the Web Audio API; no audio file is downloaded and nothing plays until you press Play.

The four waveforms

• Sine: a pure tone with a single frequency and no harmonics. It is the reference signal for hearing tests, speaker checks and acoustic measurements.
• Triangle: contains only odd harmonics that fall off quickly, so it sounds close to a sine but slightly brighter, like a soft flute.
• Square: odd harmonics that decrease slowly (1/n). It sounds hollow and buzzy, like an old video game, and is much louder than a sine at the same peak level.
• Sawtooth: every harmonic, falling as 1/n. It is the brightest, most “brassy” waveform and the starting point of many synthesizer sounds.

Because square and sawtooth waves carry more energy, this tool automatically plays them quieter than a sine at the same slider position, so switching waveforms does not make you jump.

Frequency, notes and wavelength

Musical notes use equal temperament with A4 = 440 Hz. Each semitone multiplies the frequency by the twelfth root of two (about 1.0595), and each octave doubles it: A3 is 220 Hz, A5 is 880 Hz. The formula is f = 440 × 2^((n − 69) / 12), where n is the MIDI note number. The Note list covers the 88 keys of a piano, from A0 (27.5 Hz) to C8 (4,186 Hz).

A cent is one hundredth of a semitone. When you type a frequency that is not exactly a note, the tool tells you how many cents it sits above or below the nearest one, which is useful for checking tuning references like 432 Hz.

The period is 1 / f (2.27 ms at 440 Hz) and the wavelength is the speed of sound divided by the frequency, using 343 m/s for air at 20 °C. A 50 Hz tone has a wavelength of about 6.9 m, which explains why low bass behaves so differently in small rooms.

Hearing safety

Pure tones are fatiguing and high frequencies can be loud even when they seem faint. Keep the volume low, especially above 2 kHz and with headphones, and take breaks. A warning appears when the slider goes above 60 %. Remember that this tool’s slider only sets the signal level: your device volume multiplies it.