Online tone generator

What people use a tone generator for

Checking speakers and headphones. A 100 Hz or 1 kHz sine in the left channel, then the right, tells you in two seconds whether a cable, a Bluetooth pairing or a balance setting has swapped or dropped a side. A slow sweep from 20 Hz to 200 Hz finds a rattle in a car door or a buzzing panel in a cabinet, and shows where a subwoofer really stops: most laptop speakers produce almost nothing under about 150 Hz, and small Bluetooth speakers roll off around 70 to 100 Hz whatever their box says.

Finding a hum. Mains electricity runs at 50 Hz in Europe, Africa, most of Asia and Australia, and 60 Hz in North America and parts of South America and Japan. A ground loop in a recording or a PA hums at that frequency and its harmonics. Play the matching preset quietly beside the recording and the pitch match makes the source obvious; the equalizer can then notch it out.

A tuning reference. 440 Hz is the A above middle C, the pitch orchestras and most instruments tune to. The semitone and octave buttons step from there on the equal-tempered scale, and the note name under the number shows where you are, so you can hold a drone for singing practice or check an instrument by ear. To tune against a meter instead, use the tuner.

Testing your hearing range. The 15 kHz and 17.4 kHz presets are the classic "can you hear it" tones; the second is the so-called mosquito tone that most people over 25 no longer hear. Treat it as a curiosity, not a hearing test. Laptop and phone speakers often stop well below 17 kHz, many Bluetooth codecs cut the top octave, and level matters as much as frequency. If you cannot hear a tone, try headphones before concluding anything, and see an audiologist for a real measurement.

Sine, square, sawtooth, triangle

A sine wave is a single frequency and nothing else: the pure "beep" used for measurements. A square wave adds every odd harmonic, a third as loud at three times the frequency, a fifth at five times and so on, which gives the hollow, reedy sound of old video games. A sawtooth has every harmonic, odd and even, and is the bright, buzzy starting point of most analogue synth sounds. A triangle has only odd harmonics like the square but they fall away much faster, so it sounds close to a soft sine with a little edge.

All three are generated band-limited: each is built from its harmonics up to the Nyquist limit and no further. A square wave drawn as a hard on-off edge contains harmonics far above what a 48 kHz file can hold, and they fold back down as tones that do not belong to the note. Measured here, a 5.1 kHz square drawn the naive way puts its ninth harmonic at 2.1 kHz, only 19 dB down; the one this page writes has nothing there, more than 100 dB down. For tests on filters or amplifiers, that difference is the whole point.

White, pink and brown noise

White noise has equal energy per hertz, so it sounds hissy: most of its energy is in the treble, where there are the most hertz. Pink noise falls 3 dB per octave, which puts equal energy in every octave and sounds balanced, more like rain. It is the standard signal for setting up PA systems and calibrating speakers with a real-time analyser such as REW or Smaart. Brown noise falls 6 dB per octave and rumbles like a waterfall or the inside of a plane; it is the one most people pick for sleep or masking a noisy office. The slopes are checked on every release from octave-band measurements of the generated noise.

Sweeps and binaural beats

Open Sweep and binaural to glide from the frequency above to an end frequency over a set time. The default spends equal time on each octave, which is how measurement software sweeps and how the ear hears pitch. A linear sweep spends most of its time in the treble. A sweep downloads as a single file the length of the sweep.

The binaural field raises the right ear's frequency by a few hertz, so with headphones you hear a slow beat at the difference: 200 Hz left and 210 Hz right beats ten times a second. It only works on headphones. Claims that particular beat rates focus or relax you come from small studies with mixed results, so try it if you like the sound, but it is not a treatment.

Downloading

Downloads are rendered at 48 kHz from the same maths as the preview, with 5 ms fades so the file starts and ends without a click. Choose 24-bit WAV or 32-bit float for measurement work; 16-bit gets a whisper of dither at the 16-bit noise floor, which is correct for listening and harmless for most tests. A stereo file is written only when the left and right differ, otherwise mono. To make a longer test track, add the tones together in the audio editor, or cut a ringtone from one with the ringtone maker.