Online Tone Generator

How to use the tone generator

Type a value in the Hz box or drag the slider. The slider is logarithmic, like a piano keyboard, so every octave takes up the same width and 30 Hz is as easy to set as 3,000 Hz. With the Hz box focused, the arrow keys move 1 Hz, Shift with an arrow moves 10 Hz, and Page Up or Page Down moves a whole semitone. When you are not typing in a field, the space bar starts and stops the tone.

The semitone and octave buttons step musically instead of by a fixed number of hertz, and snap, next to the nearest note, moves you onto that equal-tempered note. Every change applies to a tone that is already playing, so you can sweep while you listen. Copy link puts the frequency and waveform in the address, for example tunestand.com/tone-generator?hz=528&wave=sine. The volume is left out of the link on purpose, so a shared link never opens loud.

Which note is a frequency in Hz?

In twelve tone equal temperament every note has a fixed frequency: f = 440 x 2^((n - 69) / 12), where n is the MIDI note number and 69 is A4 at 440 Hz. Middle C (C4) is n = 60, nine semitones lower, which gives 261.63 Hz. Each semitone multiplies the frequency by the twelfth root of two, about 1.0595, and each octave doubles it.

To go the other way, work out n = 69 + 12 x log2(f / 440). The whole number nearest to n is the closest note, and the leftover fraction times 100 is the offset in cents, where 100 cents is one semitone. The 1,000 Hz test tone gives n = 83.21, so it sits 21 cents sharp of B5 at 987.77 Hz. A 100 Hz tone gives n = 43.35, which is 35 cents sharp of G2 at 98.00 Hz. The line under the readout does this calculation live, and the note frequency chart lists all 108 notes from C0 to B8.

Sine, square, triangle and sawtooth

A sine wave contains only its fundamental frequency. It sounds smooth and plain, and it is the right choice for tuning references, speaker checks and anything where you want to hear exactly one frequency. A square wave adds the odd harmonics (3, 5, 7 and so on times the fundamental) and sounds hollow and buzzy. A triangle wave also has only odd harmonics, but they fade much faster, so it sits between a sine and a square. A sawtooth contains every harmonic and sounds bright and full, close to the raw tone of a classic synth lead.

Harmonics also explain why the waveforms converge at the top of the range. A 10,000 Hz square wave has its first added harmonic at 30,000 Hz, above human hearing, so it sounds almost identical to a 10,000 Hz sine. The differences between waveforms are easiest to hear between roughly 100 and 1,000 Hz.

Safe volume and protecting your hearing

Turn your device volume down before the first play and raise it slowly. The volume slider here scales the signal before it reaches your speakers or headphones, so the real loudness depends on your hardware and system volume, and the same setting can be quiet on a laptop and very loud in earbuds. The generator fades the tone in and out over a few milliseconds, so starting and stopping never produces a sharp click.

The ear is not equally sensitive at every frequency. It is most sensitive roughly between 2,000 and 5,000 Hz, so a tone in that range sounds far louder than a 100 Hz tone at the same setting. Square and sawtooth waves also sound louder than a sine, because they carry more energy and add harmonics in that sensitive range. Turn down before you switch waveform or sweep upward.

The risk of hearing damage grows with both level and listening time. Keep test tones short, take breaks, and stop straight away if you notice ringing, muffled hearing or discomfort. High frequencies need extra care: near the top of your hearing a tone can seem faint or silent while the speaker is still producing a high level, so never turn the volume up to chase a tone you cannot hear. Children usually hear higher frequencies than adults, and dogs and cats hear well above the human range, so a tone you cannot hear may still bother someone else in the room.

What people use a tone generator for

Speaker and headphone checks. Step through the 100 Hz, 1 kHz and 10 kHz presets at low volume and listen for buzzing, rattles or distortion. A slow sweep through the low end reveals a cabinet, shelf or panel that resonates at one frequency. Small laptop and phone speakers produce very little deep bass, so a weak tone below about 100 Hz on those is normal rather than a fault.

Tuning by ear. Play a reference such as A4 for strings or E2 for the low string of a guitar, then play the same note on your instrument. When the two are close you hear beats, a slow pulsing whose rate in beats per second equals the difference in hertz. Tune until the pulsing slows and stops. For a needle display instead, use the chromatic tuner.

Tinnitus pitch matching. Some people with tinnitus use a tone generator to find the approximate pitch of the sound they hear, so they can describe it to a doctor or audiologist. That is all a tone generator can do: a matched tone is not a diagnosis or a treatment, and tinnitus that is new, one-sided or comes with hearing loss should be checked by a professional.

Exploring your hearing range. Sweeping upward shows roughly where your hearing fades, which makes a good demonstration but is not a hearing test. Consumer speakers and headphones are not calibrated and many lose output before 20,000 Hz, and the upper limit of human hearing falls with age. A real hearing test uses calibrated equipment and is done by an audiologist.