Free Online Tone and Frequency Generator

What a tone generator does

A tone generator plays a steady sound at a frequency you choose. Frequency is measured in hertz (Hz), the number of times the wave repeats each second, and you hear it as pitch. A 440 Hz tone is the A above middle C, 50 Hz is a deep hum and 10,000 Hz (10 kHz, where kHz means kilohertz) is a thin whistle.

Doubling a frequency raises it by one octave, so 220, 440 and 880 Hz are three A’s an octave apart. The 20 Hz–20 kHz range spans about ten octaves, and the slider gives each octave the same length of travel.

Changes apply while the sound plays, and the number field takes two decimal places, such as 261.63 Hz for middle C.

Note frequencies in hertz

Western instruments are tuned in equal temperament with A4 at 440 Hz. Each semitone multiplies the frequency by the twelfth root of two, about 1.0595.

Type a value from the table into the frequency field to hear the note, and double or halve it to move an octave.

Middle C is C4 at 261.63 Hz. The octave number goes up at each C, so B3 sits one semitone below C4.

Reference pitches for tuning strings

To tune by ear, play the reference and the string together and listen for beats, a slow wobble in volume. The number of wobbles per second equals the difference between the two frequencies. As the string gets closer the wobble slows down, and it stops when the two match.

A sine is the easiest reference because it has no harmonics competing with those of the string. For a low string on small speakers, a sawtooth is easier to hear.

Frequency bands and what to listen for

Audio engineers split the audible range into bands, and a tone in each one shows what an EQ (equalizer) boost or cut there will change. The guide to equalization covers the mixing side.

The 50 Hz preset matches the mains hum of power grids in Europe and much of the world. Grids in North America run at 60 Hz.

Testing speakers, subwoofers and headphones

A sine puts all of its energy at one frequency, so anything else you hear comes from the speaker, the room or something loose.

1. Start with 1 kHz at a low volume. Almost every speaker plays it cleanly, so it sets a comfortable reference level.
2. Step down through 100 Hz and 50 Hz, then type lower values in steps of 5 or 10 Hz. The point where the tone fades away is the practical low limit of your speakers.
3. Listen for a buzz that appears at one frequency and vanishes a few hertz away. It usually comes from a loose panel, a cable against a wall or an object on a shelf.
4. If a low tone sounds higher than the number on screen, the speaker is distorting and adding harmonics of its own. Turn the volume down.
5. Finish at 10 kHz, then raise the frequency slowly to find where the tweeter or your hearing stops.

The generator plays the same signal on both channels. To check left and right separately or run automatic sweeps, use the speaker test.

Finding room modes with low tones

At low frequencies the room itself shapes the bass. Sound reflects between parallel walls and builds standing waves, so at some frequencies the bass booms at your seat and at others it almost disappears.

The first of these axial modes sits at 1,125 divided by twice the distance between two walls in feet, since sound travels about 1,125 feet per second at room temperature. Further modes fall at two and three times that frequency.

To find them, sit where you listen and step a sine from 30 to 150 Hz in 2 Hz steps, noting the frequencies that jump out or drop away. Moving the subwoofer or the seat by a foot or two is the first fix to try.

Harmonics in square, sawtooth and triangle waves

Every waveform other than the sine is a stack of sine waves. The lowest, the fundamental, sets the pitch, and the harmonics at two, three and four times its frequency set the tone color.

The levels explain the sound. In a square wave the third harmonic has a third of the amplitude of the fundamental, while in a triangle it has a ninth, which is why the triangle sounds so much closer to a sine.

Harmonics also change a speaker test. A 100 Hz square wave carries energy at 300, 500 and 700 Hz, so a small speaker that cannot play 100 Hz still seems to produce the note, because the brain fills in the missing fundamental. Use a sine whenever you want to know what the speaker itself reproduces.

In subtractive synthesis, a filter removes harmonics from a sawtooth or square to shape a bass, lead or pad. The analog synths course explains how a synthesizer shapes each waveform, and the ARGEN plugin generates tones inside a DAW (digital audio workstation).

White, pink and brown noise by the numbers

Noise contains every frequency at once, in random proportions from moment to moment. Its color describes how the level changes from low to high frequencies.

Pink noise carries the same energy in every octave. To balance speakers or a subwoofer, play it, measure at the listening seat with a sound level meter or a meter app, and adjust each speaker until the readings match.

How high you can hear, and safe listening levels

Human hearing is usually given as 20 Hz to 20 kHz, but the top end drops with age and with noise exposure. Children often hear close to 20 kHz, and adults lose the highest frequencies first.

To find your own limit, play the 10 kHz preset quietly on headphones and raise the frequency slowly until the tone disappears. Laptop speakers and some headphones lose output up there too, so a low result may come from the equipment.

Ears are most sensitive between about 2 and 5 kHz. A tone there sounds far louder than a 100 Hz tone at the same volume setting, so set the level again each time you jump to a new band.

Never raise the volume to chase a frequency at the edge of your hearing. A louder tone tells you little more and puts your ears and speakers at risk.

The US National Institute for Occupational Safety and Health (NIOSH) recommends a limit of 85 dBA averaged over eight hours, and halves the time for every 3 dB above that. dBA is sound level in decibels, weighted to match the sensitivity of the ear.

A browser cannot know how loud your speakers are, so the volume slider is relative, and even at its top the generator plays at half of full scale. Start at the bottom and keep test sessions short.

Matching the pitch of tinnitus

Some people with tinnitus use a tone generator to estimate the pitch they hear and describe it to an audiologist. Use a sine at a volume just above audible.

Approach the pitch slowly from below and stop when the tone blends with the ringing. Then try double and half that frequency, because tones an octave apart are easy to confuse.

A tone generator does not diagnose or treat tinnitus. Ringing that starts suddenly, affects one ear, or comes with hearing loss or dizziness is a reason to see a doctor soon.

Using the downloaded tones in a project

Each download is a WAV file at 16-bit, 44.1 kHz, mono, the same resolution as a CD, which DAWs and video editors open without conversion. Tones fade in and out over 10 milliseconds so the file does not click at either end, and tones and noise both peak at about −6 dBFS (decibels relative to full scale).

• A 1 kHz tone at the start of a video or podcast as a level and sync reference.
• A 440 Hz sine on its own track as a tuning reference for a recording session.
• A 30-second pink noise file for matching speaker levels from a phone.

To hear several tones together, such as a chord, download each one and stack them on separate tracks in a DAW.